Impact of Processing on Potato Phytochemicals Amber Nicole Furrer Purdue University

Purdue University Purdue e-Pubs

Open Access Theses Theses and Dissertations

January 2015 Impact of Processing on Potato Phytochemicals Amber Nicole Furrer Purdue University

Follow this and additional works at: https://docs.lib.purdue.edu/open_access_theses

Recommended Citation Furrer, Amber Nicole, "Impact of Processing on Potato Phytochemicals" (2015). Open Access Theses. 1108. https://docs.lib.purdue.edu/open_access_theses/1108

This document has been made available through Purdue e-Pubs, a service of the Purdue University Libraries. Please contact [email protected] for additional information. Graduate School Form 30 Updated 1/15/2015

PURDUE UNIVERSITY GRADUATE SCHOOL Thesis/Dissertation Acceptance

This is to certify that the thesis/dissertation prepared

By Amber N. Furrer

Entitled Impact of Processing on Potato Phytochemicals

For the degree of Master of Science

Is approved by the final examining committee:

Mario Ferruzzi Chair Bill Aimutis

Fernanda San Martin-Gonzalez

To the best of my knowledge and as understood by the student in the Thesis/Dissertation Agreement, Publication Delay, and Certification Disclaimer (Graduate School Form 32), this thesis/dissertation adheres to the provisions of Purdue University’s “Policy of Integrity in Research” and the use of copyright material.

Approved by Major Professor(s): Mario Ferruzzi

Approved by: Mario Ferruzzi 7/28/2015 Head of the Departmental Graduate Program Date

IMPACT OF PROCESSING ON POTATO PHYTOCHEMICALS

A Thesis Submitted to the Faculty of Purdue University by Amber N Furrer

In Partial Fulfillment of the Requirements for the Degree of Master of Science

August 2015 Purdue University West Lafayette, Indiana

For Ana Steen, my partner in crime and friend through all the ups and downs.

i i

iii

ACKNOWLEDGEMENTS

This thesis and the work therein was directly supported and influenced by my advisor, Mario Ferruzzi, Anne Kurilich of McCain Foods, and my committee members Bill Aimutis and Fernanda San Martin-Gonzalez. Thank you for all of your guidance and advice. This thesis and the work therein was indirectly supported by the grace of God, my family, friends and fellow grad students, and many cups of coffee, which I only started drinking in graduate school. I would like to specifically thank my lab mates Tristan, Sydney, Ben, Dennis, Darwin, and Ingrid for all of their help when I needed it. It was a pleasure working with all of you, and I couldn’t have asked for a better lab group. To the lunch table- thanks for brightening my days. To all of my friends in grad school, thank you for sharing these past two years with me and putting up with all of my shenanigans. I will miss each and every one of you.

i i i

TABLE OF CONTENTS

Page LIST OF TABLES ...... vii

LIST OF FIGURES ...... viii

LIST OF ABBREVIATIONS ...... ix

ABSTRACT ...... x

CHAPTER 1. LITERATURE REVIEW ...... 1

1.1 Introduction ...... 1

1.2 Potato Varieties, Cultivation, and Forms in the Diet ...... 3

1.2.1 Potato Variety and Selection ...... 4

1.2.2 Cultivation, Harvest, and Storage ...... 7

1.2.3 Value-Added Commercial Processing of Potatoes ...... 8

1.3 In-Home Processing ...... 10

1.4 Nutritive Value and Perception of Potatoes & Potato Products ...... 12

1.4.2 Protein ...... 17

1.4.3 Lipid ...... 19

1.4.4 Vitamins ...... 20

1.4.5 Minerals ...... 21

1.5 Potato Bioactive Phytochemicals Content and Bioavailability ...... 23

1.5.1 Phenolic Acids and Flavonoids ...... 23

1.5.2 Carotenoids and Tocochromanols ...... 28

1.5.3 Glycoalkaloids ...... 30 i v

Page

1.5.4 Factors Impacting Phytochemical Content in Potatoes and Potato Products . 31

1.5.5 Bioavailability of Phytochemicals in Potatoes ...... 38

1.6 Health Benefits of Potatoes and Potato Products ...... 42

1.6.1 Contribution to Dietary Nutrients of Concern and Bioactive Compounds ...... 42

1.6.2 Potatoes and Risk of Chronic Diseases ...... 44

1.6.3 Potatoes and Modulation of Oxidative Stress ...... 46

1.6.4 Potatoes and Modulation of Inflammatory Stress ...... 47

1.6.5 Glycemic Effect of Potatoes ...... 48

1.6.6 Potato Influences on the Microbiota ...... 51

1.7 Opportunities to Improve Nutritional Value of Processed Potato Products ...... 51

1.7.1 Lipid Reduction ...... 52

1.7.2 Resistant Starch Formation ...... 53

1.7.3 Management of Acrylamide Formation ...... 55

1.8 Research Needs and Future Directions ...... 55

CHAPTER 2. RESEARCH RATIONALE AND OBJECTIVES ...... 58

CHAPTER 3. PHYTOCHEMICAL CONTENT IN COMMERCIALLY RELEVANT POTATO VARIETIES AND PROCESS STABILITY IN COMMERCIAL AND FRESH POTATO PRODUCTS. 60

3.1 Abstract ...... 60

3.2 Introduction ...... 61

3.3 Materials and Methods ...... 64

3.3.1 Chemicals and Standards ...... 64

3.4 Sampling and Processing Procedures ...... 64

3.4.1 Experiment 1: Preparation of Fresh Potatoes for Determination of Phytochemical Content ...... 64

Page

3.4.2 Experiment 2: Sampling of Commercially Processed Samples for Determination of Phytochemical Content ...... 65

3.4.3 Experiment 3: Sampling and Reconstitution of Commercially Processed Frozen Products for Comparison of Phytochemical Content...... 65

3.4.4 Experiment 3: Preparation of Freshly Prepared Products for Comparison of Phytochemical Content...... 66

3.4.5 Phenolic Acid and Anthocyanin Extraction and Analysis...... 68

3.4.6 Carotenoid Extraction and Analysis ...... 69

3.4.7 Statistical Analysis ...... 70

3.5 Results and Discussion ...... 71

3.5.1 Experiment 1: Phytochemical Content in Fresh Commercial Varieties ...... 71

3.5.2 Experiment 2: Chlorogenic acid and Anthocyanin Content Through Commercial Processing...... 78

3.5.3 Experiment 3: Comparison of Chlorogenic Acids and Beta-Carotene in Fresh and Commercially Produced Potato Products...... 85

3.6 Conclusions ...... 90

CHAPTER 4. GENERAL FINDINGS AND FUTURE DIRECTIONS ...... 91

LIST OF REFERENCES ...... 94

APPENDICES

Appendix A. Other phytochemicals detected but not quantified in potatoes……………….115

Appendix B. Chlorogenic acid content in raw Covington potatoes destined for sweet potato fries and wedges……………………………………………………………………………………………....116

Appendix C. Nutritional data and % moisture for raw potato varieties……………………...117

Appendix D. Nutritional data for commercial and fresh processed potato products…...118

Appendix E. PDCAAS data for raw varieties……………………………………………………………..119

v i

vii

LIST OF TABLES

Table Page Table 1. Common US fresh market potato varieties and uses ...... 5 Table 2. Common Commercial Potato Products Grouped By Processing Type ...... 11 Table 3. Proximate composition and nutritive value of potatoes, potato products, and comparable carbohydrate sources per 100 g of product ...... 14 Table 4. Potato phytochemicals: Range of content of main phytochemicals in key commercial and select specialty varieties, grouped by phytochemical and potato flesh color ...... 25 Table 5. Effects of several processing methods on potato phytochemical content, grouped by processing type and author...... 35 Table 6. Percent of dietary nutrient provided by potato for US adults (1994-96) and rank among 112 food/food groups ...... 43 Table 7. CQA and caffeic acid in whole potatoes and potato flesh of nine commercial potato varieties and one commercial sweet potato variety...... 73 Table 8. Anthocyanin content of three pigmented potato varieties, expressed by class of anthocyanidin...... 76 Table 9. CQAs in four varieties of potatoes through various levels of commercial processing...... 82 Table 10. Anthocyanins in three pigmented varieties of potato through various levels of commercial processing, expressed by class...... 84 Table 11. Chlorogenic acids in freshly prepared and commercially processed products. ... 87

v i i

viii

LIST OF FIGURES

Figure Page Figure 1. Structures of primary phytochemicals found in Solanum tuberosum varieties. ... 27 Figure 2. Overview of the digestion and intestinal absorption of phytochemical from potatoes...... 39 Figure 3. Schematic of commercially processed potato samples obtained from McCain foods for phenolic and anthocyanin analysis...... 65 Figure 4. Preparation of samples for Experiment 3- comparison of CQAs and beta-carotene in commercially processed and freshly prepared products...... 67 Figure 5. Average total CQA’s in flesh and whole of nine commercial Solanum tuberosum varieties...... 74 Figure 6. Example anthocyanin chromatograms for three varieties of pigmented potato: (1) ADR, (2) ADB, (3) AR2009-10 ...... 77 Figure 7. Example chromatogram of the Norland variety, whole. m/z 353- CQA; m/z 179- caffeic acid...... 80 Figure 8. Total CQAs (sum of averages of 3-,4-, and 5-O-CQAs) quantified in four varieties of commercially processed potatoes ...... 81 Figure 9. Total anthocyanins (sum of averages of individual anthocyanidins) quantified in three varieties of commercially processed potato...... 85 Figure 10. Total CQA’s (sum of averages of 3-,4-, and 5-O-CQA) compared in commercial and fresh products...... 88 Figure 11. Total CQAs (sum of averages of 3-,4-, and 5-O-CQA) compared in commercial and fresh products…………………………………………………………………………………………………………88 Figure 12. Beta-carotene content in fresh and commercial products...... 89

v i i i

LIST OF ABBREVIATIONS

CQA Caffeoylquinic acid (Chlorogenic acid)

FWS Flesh with skin (whole)

FNS Flesh

BF Blanched, frozen

BFM Blanched, frozen, microwaved

BFF Blanched, fried, frozen

BFFF Blanched, fried, frozen, fried

BFFO Blanched, fried, frozen, fried

i x

ABSTRACT

Furrer, Amber, N. M.S. Purdue University. August 2015. Impact of Processing on Potato Phytochemicals. Major Professor: Mario G. Ferruzzi.

Potatoes (Solanum tuberosum) are an important staple crop in both developed and developing countries around the world. These tubers offer an important source of nutrients, micronutrients, and health-promoting phytochemicals to the diet. However, reported content and process stability of phytochemicals in commercial potatoes and potato products is inconsistent. The objectives of this research were to compare phytochemical content in white/yellow and pigmented commercially relevant varieties, determine changes in phytochemical content of select potato varieties through commercial processing, and assess differences in phytochemical content between freshly “home” prepared and reconstituted, commercially processed white and sweet potato products. To carry out the first objective, phenolic acids, anthocyanins, and carotenoids were analyzed in whole and flesh of nine commercial potato varieties. Total chlorogenic acids (CQAs), the primary phenolic acid in potatoes, ranged from 43-953 mg/100 g dw and were found in greater concentrations in the whole of all varieties compared to flesh, suggesting concentration in the peel. Higher levels of CQAs were also observed in in pigmented potatoes compared to white/yellow-fleshed potatoes (318-953 and 43-88 mg/100 g dried whole potato, respectively). 5-O-Caffeoylquinic acid (5-CQA) was the primary chlorogenic acid isomer detected in all varieties of potato, followed by 4-O- and 3-O-caffeoylquinic acid (4-CQA and 3-CQA). Acylated anthocyanins in red potatoes were primarily cyanidin and pelargonidin derivatives, while those in purple varieties were primarily derivatives of petunidin with smaller amounts malvidin and delphinidin. For the second objective, four varieties (2 purple, 1 red, 1 white) of processed, dried, and ground commercial products were obtained from McCain foods, including raw flesh without skin (FNS), blanched+frozen (BF), +microwaved (BFM), and blanched+par- x

fried+frozen (BFF), +baked (BFFO) or +fried (BFFF). Retention of phenolics ranged from 49-85% for pigmented varieties and 32-55% for white. For purple and red varieties, CQA levels were significantly lower (p<0.05) in BFF, BFFO, and BFFF compared to FNS, BF, or BFM products. For white, CQA levels were lower (P<0.05) in all processed products compared to FNS, but no differences were observed between processing levels. Retention of anthocyanins through all forms of processing was found to be high (69-129%). For the last objective, CQA and beta-carotene were compared in freshly prepared versus commercially produced and reconstituted classic fries, fresh-style fries, hash browns, sweet potato fries, and sweet potato wedges. Levels of CQA did not differ for classic fries, fresh-style fries, or sweet potato fries, but were significantly (p<0.05) lower in industrial baked and fried sweet potato wedges and baked and pan-fried hash browns. Sweet potato -carotene was higher in commercial baked wedges (30 mg/100g dw) compared to fresh prepared (26 mg/100g) (p<0.05), but no other differences between fresh and commercial products were found. These results suggest that commercial blanching, freezing, and microwaving have an overall mild impact on phytochemical levels in raw potatoes compared to par-frying and subsequent baking or frying. Additionally, industrial products compare favorably to freshly prepared products in recovery of phytochemicals suggesting that both commercially prepared and freshly prepared products would provide similar delivery of health promoting phytochemicals.

x i

CHAPTER 1. LITERATURE REVIEW

Introduction

The potato (Solanum tuberosum) is currently the fourth most important agricultural crop, after rice, wheat, and corn, grown for human consumption (USDA Economic Research Service, 2014). Potatoes are known to have high agricultural yields and significant nutritive value as a source of macronutrients (carbohydrate and protein), micronutrients (vitamin C, potassium, magnesium) and potentially healthful phytochemicals (Camire et al., 2009). This, combined with the ability of potato varieties to be grown, processed and transformed in many temperate as well as tropical/subtropical regions of the world (Govindakrishnan and Haverkort, 2006), gives this tuber the potential to impact several dimensions of health and nutrition ranging from under-nutrition and basic food security to products associated with over-nutrition. Since initial domestication by natives of the Central Andes in South America almost 8000 years ago (Food and Agriculture Organization of the United Nations, 2008a) the potato has been consistently bred and improved resulting in tremendous diversity over 4500 cultivated varieties (“New World Catalogue of Potato Varieties,” 2009). Two main subspecies exist, S. tuberosum: andigena, known as Andean; and S. tuberosum, or Chilean (Zaheer & Akhtar, 2014). S. tuberosum varieties remain the most commonly grown and consumed representing ~10% of cultivated species and over 200 wild species (Global Crop Diversity Trust and FAO Plant Production and Protection Division, 2008). Tremendous variation in physical (size, shape and color), organoleptic, and nutritional quality exists in commonly consumed potatoes, providing an opportunity to meet an array of food requirements around the world. In the developing world, the need exists to diversify the diet with nutritious and high yielding crops that can endure less-than-ideal conditions (Bradshaw, 2007). The potato is a critically important “food security” crop for many developing nations, as it is not traded as a commodity and thus is less vulnerable to world

food price increases. Many countries have begun to use potatoes to reduce their dependence on commodity crops, and in 2005, for the first time, the share of potatoes produced by developing nations surpassed that of developed nations (FAO Trade and Markets Division, 2008). In the developed world, there is need for varieties which are high- yielding, pest-resistant, and sustainably-produced to meet the growing convenience, specific health, and quality demands of consumers (Bradshaw, 2007). While global consumption of potatoes is increasing, in developed markets such as the US, consumption of fresh potatoes is actually decreasing relative to consumption of commercially processed potatoes (frozen, fried, chips and snacks) which is increasing (USDA Economic Research Service, 2014). This increase in prevalence and preference of processed products is often met with criticism due to the perception that processed potato products do not deliver the same nutritional value as freshly prepared products. In fact, while potatoes in their raw state are an excellent source of key nutrients and phytochemicals, both traditional (in home) and commercial processing and preparation methods can result in loss of micronutrients and other perceived negative nutritional changes including addition of fat and salt as well as conversion of natural resistant starch to highly digestible starch (Ek et al., 2012). Considering the diversity of potato varieties and processing technologies, opportunities exist to leverage basic principles of food science and technology to improve the nutritional profile of potatoes in all forms from basic in-home products to processed products including meal components and snacks. The purpose of this review is to summarize key information on potatoes and potato products commonly consumed as key source of nutrients and biologically active phytochemicals and describe the state of the science relative to the impact of processing (in home and commercial) on nutritional quality and health impacts of potato products. As several reviews already exist on potato genetics and agronomic characteristics (Arvanitoyannis et al., 2008; Mori et al., 2015; Watanabe, 2015), the nutritional quality and impact of potato (Brown, 2005; Camire et al., 2009; Ezekiel et al., 2013; King and Slavin, 2013; McGill et al., 2013), and overall contribution of potato products to the human diet (Keijbets, 2008; Zaheer and Akhtar, 2014), this literature review strives to build on these previous efforts and includes discussion of research gaps, novel technologies, and potential targets that can be leveraged to enhance the value of this critically important food product in all forms in the human diet.

Potato Varieties, Cultivation, and Forms in the Diet

As of 2014, China ranked first in global potato production, followed by Russia, India, and the United States (USDA Economic Research Service, 2014). However, the United States, the Netherlands, Germany, and Canada lead the world in production of processed potato products (Keijbets, 2008). As of 2008, world per capita consumption of potatoes (average 31 kg) was led by Europe (88 kg), followed by North America (60 kg), then Asia (24 kg), Latin America (21 kg), and Africa (14 kg). However, when total consumption was considered, Asia/Oceania was the global leader with 94 million tonnes, followed by Europe at nearly 65 million tonnes (Food and Agriculture Organization of the United Nations, 2008b). In the United States consumption of fresh potatoes has decreased from 81 lbs/capita/year in 1960 to 42 lbs/capita/year in the 2000’s. This drop in fresh potato consumption was marked by an increase in processed potato consumption to 55, 17, and 14 lbs/capita/year of frozen potato products (mostly French fries), potato chips, and dehydrated potato products (including flakes and potato flour), respectively (USDA Economic Research Service, 2014). Changes in consumption patterns have implications for the nature and quality requirements of potatoes from cultivation through harvest and processing. The following sections will briefly review common potato varieties and the selection of varieties for fresh market and commercial production of potato products, potato cultivation, post-harvest handling, and processing. For more in depth information see additional references: (Pieterse and Hils, 2009), (Jai Gopal and S. M. Paul Khurana, 2006), (Hawkes, 1990), (Vreugdenhil et al., 2011).

1.2.1 Potato Variety and Selection

Potato varieties can vary significantly in physical and chemical characteristics, nutrients, micronutrients, and phytochemicals. The genetic diversity of potatoes has made it possible to breed for specific functional and nutritional qualities critical to producers and consumers alike. Potato varieties have been broadly characterized by many features of both the plant and tuber. Some characteristics relating to the tuber include orientation relative to the stolon (stem connected to root), shape, number of buds, or ‘eyes’, skin texture, skin and/or flesh color and distribution of pigmentation, maturity type, and disease resistance (Burton, 1989). Potatoes are also categorized based composition, cooking quality characteristics, and use. In 1926, Salaman described four categories: floury (often burst spontaneously, crumble easily), close (do not burst, readily break, don’t crumble), waxy (firm flesh, only breaks down by kneading), and soapy (same as waxy, but also watery and translucent). These differences in texture correspond to differences in starch type and content. Floury potatoes contain more starch than other varieties (20-22%) with a high proportion of amylose, giving them a drier, mealier texture. Waxy potatoes contain lower amounts of starch (16-18%) with a high proportion of amylopectin. Starch type and content contribute to performance differences in certain dishes (see discussion below). The British Potato Council provides a categorization of popular fresh market varieties as “fluffy” (13 varieties), “salad” (18 varieties), and “smooth” (20 varieties) (Agriculture and Horticulture Development Board: Potato Council, 2012). Relative to industrial processing, the US Potato Board summarizes 15 major varieties used for chip stock in the United States: Alturas, Andover, Atlantic, Chipeta, Dakota Pearl, Ivory Crisp, Kennebec, LaChipper, Marcy, Megachip, NorValley, Norwis, Pike, Reba, and Snowden (United States Potato Board, 2007a). Other varieties, like Russet Burbank and Shepody, are more suitable for French fry production (Keijbets, 2008). Cultivar use for processed potato production varies by country (Keijbets, 2008).

Table 1. Common US fresh market potato varieties and uses (United States Potato Board, 2007b).

Type Description/Notes Common Varieties Most common variety High in starch, floury Burbank, Norkotah, Russet All purpose, good for baking, frying, Ranger, Shepody roasting and mashing

Medium starch Thin skin Atlantic, Katahdin, Round White Creamy texture Norwis, Reba, Superior All purpose, good for salads, scalloped dishes, steaming, frying, roasting Medium starch Firm, creamy texture Kennebec, White Rose, Long White All purpose, good for boiling, Cal-White microwaving, and pan frying Firm, smooth, waxy texture Chieftain, Dakota Often found as "new potatoes" Red Rose, La Rouge, Good for salads, roasting, boiling, and Norland, Red La Soda steaming

Dense, creamy texture Mild buttery flavor Yukon Gold, German Yellow Good for mashing, roasting, baking, Butterball, Sierra Gold boiling, and steaming

Mainly available in fall Purple Peruvian, All Blue and Subtle nutty flavor Blue, Congo, Lion's Purple Good for microwaving, salads, steaming, Paw, Vitillete, Purple grilling, and baking Viking, Purple Majesty

Restaurant trend Russian Blue, Red Firm, waxy texture Fingerlings Thumb, French Russian Good for steaming, boiling, baking, and Banana salads More concentrated flavor Petite, or New Always starchier than their mature C-size and smaller of Potatoes counterparts any potato variety Good for salads, roasting, frying

Breeding and selection of varieties is dependent on several factors that can be broadly separated on the intended use of the potato, specifically fresh market or for further processing. However, several of these factors clearly overlap. For fresh market potatoes, critical characteristics include shape and overall appearance (free from blemishes and defects). Consumers have rated appearance of the skin and location of growth (interest in “locally grown”) as important factors in potato purchasing (Jemison et al., 2008). Cooking quality is important as it relates to color, texture, and flavor of the final dish. For example, selection is often based on stability to preparation and absence of cooking defects such as enzymatic browning- resulting from oxidation of tyrosine through reactions catalyzed by polyphenoloxidase- and stem-end blackening- resulting from a reaction between iron and chlorogenic acid (Burton, 1989, chap. 11; Storey, 2007). Starch type and content greatly affects performance in different dishes. For example, high starch and high amylose potatoes are most appropriate for baking, mashing, and frying due to their more crumbly texture and because amylose molecules separate easily when cooked in water (Hassanpana et al., 2011). In contrast, high amylopectin varieties hold together better upon boiling (Dresser, 2007). The common uses of several types of fresh market varieties are found in Table 1. Selection of commercial varieties can be more complicated considering both the commercial process and in some cases the in home final preparation (for products such as frozen potatoes). All of the “fresh market” characteristics are also important for potatoes used in commercial processing, with the addition of more specific factors. In general, potatoes should be uniform and not disfigured, without sprouts or blemishes, and within an appropriate size range depending on the application. A short, oval shape with a transverse axis ratio less than 1.33:1 is desired for chip manufacturing. In French fry manufacturing, long varieties are desirable (transverse axis greater than 50 mm). Dry matter concentration is also important; dry matter less than 19.5% and 20% for French fry and chip manufacturing, respectively, is considered unacceptable (Kirkman, 2007). Final color (control of excessive browning) is a critical component of quality in fried potato products, which is a result of reactions occurring during heating between both reducing sugars and sucrose (especially at higher temperatures) and amino acids (Shallenberger et al., 1959). The amino acid glutamine has been highly associated with dark fry color in crisps, as well as arginine, asparagine, and others, depending on concentration of reducing sugar (Khanbari and Thompson, 1993). Thus, lowering sucrose and reducing

sugar content in addition to certain amino acids in commercial varieties is desired to limit darkening. This is also a critical factor in controlling acrylamide formation. A byproduct of the Maillard reaction, acrylamide is considered a potential carcinogen (Tareke et al., 2000) produced from the reaction of reducing sugars and the amino acid asparagine, which is abundant in potatoes, during high heat (>1200C) processing including baking, frying and roasting. Reducing sugar concentration is the limiting portion of the reaction, and therefore steps taken to lower reducing sugars in potatoes are a key strategy to control acrylamide formation in final processed products (Kirkman, 2007). Several factors impact sugar concentration, including genetic characteristics, weather patterns and agronomic practices during growth, maturity at harvest, and temperature and air composition during storage (Kirkman, 2007). Concentration of free amino acids, citrate, phosphate, and vitamin C may also have an effect on browning reactions (Burton, 1989, chap. 11). Additional important functional and nutritional factors in variety selection for commercial processing include type of starch, high yields, improved micronutrient and antioxidant content, reduction in anti-nutritional components such as glycoalkaloids and acrylamide precursors, and resistance to various environmental stresses, pests, and diseases (Bradshaw and Bonierbale, 2010; Jansky, 2009).

1.2.2 Cultivation, Harvest, and Storage

Potatoes are grown from “seed potatoes”, which can comprise 5-15% of a year’s crop. They can be grown in a variety of climates, but cannot flourish at temperatures less than 10°C (50°F) or more than 30°C (86°F) (Food and Agriculture Organization of the United Nations, 2008a). High temperatures during growth and storage advance potato physiological aging- a combination of chronological age and environmental conditions which affects composition and sensory qualities (Wszelaki et al., 2005). Potatoes which age faster and reach the incubation (sprouting) phase of growth earlier will have a higher sugar content and lose significantly more water. The speed at which a potato advances into the incubation phase is determined by variety, maturity at harvest, weather and soil conditions during growth, and irrigation. Cool, wet weather is considered ideal for growth (Govindakrishnan and Haverkort, 2006). While potatoes are quite adaptable to different soil and growing conditions, the best soils are rich in organic matter and loose and loamy to allow for appropriate aeration and drainage (Thornton and Sieczka, 1980). 7

Typical yields (tonnes/hectare) for potatoes are reported to be highest in North America (41), followed by Europe (17), Latin America (16), Asia (15), and Africa (10) (Food and Agriculture Organization of the United Nations, 2008b). The size of the potato harvest in the United States continues to expand, due to both increases in land area and average yields. In 2013, US farmers harvested 467 million hundredweight (cwt) of potato tubers (Wells et al., 2013). Potato tubers are harvested when at maturity, usually determined by a sucrose rating test (levels should be less than 1 mg/g fw). 90% of potato harvest occurs in the fall, but many varieties are suited for long-term storage in climate controlled conditions. This allows them to be sold throughout the year to both the fresh and processing markets. Fresh market potatoes are sold on the open market upon harvest, while potatoes intended for commercial processing are usually contracted before spring planting (USDA Economic Research Service, 2014). Potatoes that are meant to be stored can be left in the soil to allow skins to thicken, which helps to prevent moisture loss (Food and Agriculture Organization of the United Nations, 2008a). Stored potatoes should not be washed first to minimize spread of disease and limit moisture. However, potatoes intended for processing should be stored in a dark area at high relative humidity, and between 6-8°C to prevent greening or loss in quality (Bradshaw and Ramsay, 2009; Food and Agriculture Organization of the United Nations, 2008a). Colder temperatures during storage lead to accumulation of reducing sugars, which increase sweetness, promote excessive darkening during frying, and as described previously, can contribute to acrylamide formation (Amrein et al., 2003). For additional information on storage, as well as sprouting inhibition, see Gopal and Khurana (2006).

1.2.3 Value-Added Commercial Processing of Potatoes

Early processing of potatoes had the goal, similar to that for most perishable foods, of minimizing spoilage and extending shelf-life. In this regard, dehydration was uniquely suitable for potatoes. Early examples of processed potatoes can be traced to the Incan Empire (~1400 A.D.), which created a dehydrated product known as chuño, made through a natural freeze drying process leveraging the conditions of the Andean region (Bradshaw and Ramsay, 2009). This product is still made today in some South American communities (Kirkman, 2007). The first reference to more modern processed potato products appeared in France around 1780 describing dehydrated potato biscuits (Burton, 1989, chap. 9). In 8

1845, Charles Edwards filed a US patent for the first dehydrated potato process, in which potatoes were pressed and dried on tubes heated with steam (Edwards, 1845). In general, dehydrated products were the most common potato product until the second half of the 20th century, at which point more diverse forms of processed potato products became increasingly popular (Bradshaw and Ramsay, 2009). Currently, around 50-60% of fresh potatoes undergo commercial processing in some form. This includes transformation into chips, frozen potato products (mostly French fries), dehydrated potato products (including flakes, granules, flour, meal, and dried potatoes), chilled-peeled potatoes (mostly in Europe), canned potatoes, and other potato products (Bradshaw and Ramsay, 2009; USDA Economic Research Service, 2014). Potato products with significant market presence driven by consumer and restaurant demand are summarized in Table 2. Frozen French fries are the United States’ top potato export product (valued at $635 million), followed by potato chips ($178 million), and dehydrated potato products ($82 million) (USDA Economic Research Service, 2014). Beyond typical application in potato based food products, potatoes are also processed into potato starch, and also fermented into alcoholic beverages or as feedstock for pharmaceutical, textile, paper, and other industries. Examples of these products include biodegradable plastic substitutes, fuel-grade ethanol, and farm animal feed (Food and Agriculture Organization of the United Nations, 2008a). These kinds of products are important to consider as potential avenues for waste stream disposal. Many other applications exist for use of potato processing waste. Potato juice secondary stream obtained from potato starch processing can be used as a high quality protein source for further applications (Kärenlampi and White, 2009). Potato peelings contribute certain superior functional and nutritional properties and have been successfully used to replace wheat bran as a fiber source in bread (Toma et al., 1979). Potato peel waste is also rich source of polyphenols (Mattila and Hellström, 2007) and minerals, especially iron (Tarazona-Díaz and Aguayo, 2013). According to Maeder, et al. (2009), waste mash from dried potato flake processing contained similar amounts of glycoalkaloids and phenolic compounds as the final commercial product, making it a suitable byproduct to consider for animal feed. Data from Rodriguez de Sotillo et al. (1994) suggests that antioxidant activity of freeze-dried potato peel extract compared to that of BHA (butylated hydroxyanisole). Use at 200 ppm in foods kept concentrations of glycoalkaloids below toxicity thresholds (discussed in Section 4.3). The ability to leverage

these secondary product streams and capture beneficial compounds from potato waste streams may prove useful for future applications and aid in enhancing sustainability of potatoes in all forms. This would require consideration of safety and quality of waste streams (including pesticide residue and glycoalkoloid content) but also investment into processing lines suitable for transforming these products into usable materials or intermediates.

In-Home Processing

While processed potato products remain the primary end use, a significant portion (40~50%) of potatoes are distributed and sold on the fresh market to be used in homes and for food service applications. Fresh potatoes that are home-grown or purchased in the fresh market are processed/prepared, in order of popularity, via boiling/steaming, baking/roasting, frying, microwaving, and other methods (Vreugdenhil et al., 2011). Variations within each of these methods can produce hundreds of recipes, including soups, salads, mashed potatoes, baked potato dishes, dumplings, pancakes, French fries, and on. Other than differences in scale and intensity, approaches in home are similar to those employed in commercial operations relying on similar unit operations such as peeling, size reduction (slicing, cubing, etc.), thermal treatment, roasting, baking, boiling and frying. One exception may be commercial French fry processing. Industrially, French fries often undergo par frying and frying before consumption, which means there are two opportunities for heat and mass (water for oil) transfer at the surface of the potato.

1 0

Table 2. Common Commercial Potato Products Grouped By Processing Type (Bradshaw and Ramsay, 2009; Kirkman, 2007).

Product Category Common Products Sold in USA Snacks Potato chips Sheeted or extruded products Frozen Products Baked, frozen whole potatoes and half shells Blanched, IQF slices or cubes Dehydro-frozen dices Hash Browns, patties, tots French fries, crinkle cut, waffles, wedges, curly Various child products Dehydrated Potato Standard flakes Products Standard flakes, ground Low peel flakes Flour Granules Slices, dices, and shreds

Nutritive Value and Perception of Potatoes & Potato Products

The nutritional value of potatoes and their derived products have long been misunderstood by many consumers, based in part on the manner in which potatoes are processed and prepared as well as the assumption that all potatoes result in high glycemic response. In 1973, a survey of British women showed that 65% considered potatoes to be fattening, 13% thought they provided a good source of energy, and only 2% thought that they had any nutritional value (Burton, 1989, chap. 10). A study by Monteleone, et al. (1997) revealed that in general, participants viewed potatoes in general as “filling”, and boiled and baked potatoes were seen as “healthy”. However, these preparations were also seen as bland and boring. Chipped and roast potatoes were viewed as more flavorful, but they were also rated as highly fatty and fattening. Fearne (1992) also observed positive attitudes in a population of British consumers. In regards to starch content, a study of UK consumers revealed that participants thought starch-rich foods like potatoes were high in energy and wouldn’t help them control weight (Stubenitsky and Mela, 2000). Results of a study on “good foods gone bad” by Oakes (2004) showed that if a food contained added fat and sugar (e.g. baked potato with sour cream), it was considered by respondents to be lower in vitamins and minerals than the corresponding primary food alone (baked potato, skin on). Participants viewed French fries as “very, very fatty” and “just carbs and fat”, and stated that “fatty foods have no vitamins”. Spinach and potatoes (baked/skin on) contained the highest overall levels of vitamins and minerals per serving out of 17 primary foods tested including apples, strawberries, raisins, peanuts, carrots, mushrooms, milk, and corn. However, respondents considered spinach, carrots, and apples highest in vitamins and minerals (both carrots and apples would actually be close to the bottom of the list). Overall, the study conveys that perception of the nutritional value of potatoes is strongly influenced by factors (possibly historical, social, and cultural) other than their nutrient and micronutrient content. In addition, this perception is strongly influenced by presence of added fat. In reality, potatoes are an inexpensive staple source of energy, contain relatively high amounts of high-quality protein compared to other vegetables and starchy foods, and are an important source of vitamin C, potassium, and other key micronutrients. However, as stated previously, potatoes are often prepared and served with ingredients such as salt and fat to increase their palatability, and fully gelatinized potato starch in these products

contributes to a high glycemic index. Considering the complexity and variation in preparation, it is more difficult to determine the nutritional benefits of potato products with increased sodium and fat content of finished products (Table 3). This is further complicated if the context of the full finished product or meal is not considered. Furthermore, potato preparation practices are known to influence micronutrient and phytochemical profiles through thermal degradation and leaching (reviewed in Decker and Ferruzzi, 2013). In that context, the nutritional perception of processed potatoes should include their carbohydrate content, in the form of starch, protein content/quality, fiber and presence of key micronutrients including potassium, magnesium and vitamin C (Table 3). When compared to other common sources of starch in the diet- cooked pasta or brown rice- a serving of potatoes (with skins) contains less energy and carbohydrates and contains more fiber, iron, Vitamin C, folate, and Vitamin B6 (US Department of Agriculture Agricultural Research Service, 2014). While promising, these data do not take into account the considerable diversity that exists in raw potato nutritional quality (Augustin, 1975), which represents an opportunity to leverage breeding/selection and agronomic practices to maximize the nutritional value of potato products. Combined with post-harvest and processing strategies (discussed later) significant opportunities exist to better position potato nutritional perception and value for consumers.

1 3

Table 3. Proximate composition and nutritive value of potatoes, potato products, and comparable carbohydrate sources per 100 g of product (US Department of Agriculture Agricultural Research Service, 2014).

Component Unit Potato Sweet Potato Potato, Potato, Macaroni, Brown Rice, Potato Chips, French Fries DRV/ w/ Skin, Raw1 Raw2 Flesh, Boiled w/ Skin, Baked Unenriched, Long grain, Plain, Salted7 Frozen, Baked, RDI w/ Salt3 w/ Salt4 Cooked5 Cooked6 w/ Salt8 Moisture g 79 77 77 75 62 73 1.9 64 Energy kcal 77 86 86 93 158 111 532 158 2000 Protein g 2.0 1.6 1.7 2.5 5.8 2.6 6.4 2.8 50 Fat g 0.09 0.05 0.1 0.13 0.9 0.90 34 5.5 300 Carbohydrate g 17 20 20 21 31 23 54 26 300 Total Sugars g 0.78 4.2 0.85 1.1 0.56 0.35 0.33 0.37 Fiber g 2.2 3.0 2.0 2.2 1.8 1.8 3.1 2.0 25 Potassium mg 421 337 328 535 44 43 1196 478 4700 Phosphorus mg 57 47 40 70 58 83 153 87 1000 Magnesium mg 23 25 20 28 18 43 63 24 400 Calcium mg 12 30 8 15 7 10 21 12 1000 Sodium mg 6 55 241 10 1 5 527 324 2300 Iron mg 0.78 0.61 0.31 1.1 0.50 0.42 1.3 0.57 18 Zinc mg 0.29 0.30 0.27 0.36 0.51 0.63 1.1 0.35 15 Thiamin mg 0.08 0.08 0.10 0.06 0.02 0.10 0.21 0.13 1.5 Niacin mg 1.1 0.56 1.3 1.4 0.40 1.5 4.8 2.1 20 Riboflavin mg 0.03 0.06 0.02 0.05 0.02 0.03 0.09 0.03 1.7 Vitamin B6 mg 0.30 0.21 0.27 0.31 0.05 0.15 0.53 0.26 2 Folate ug 16 11 9 28 7 4 29 23 400 Vitamin B12 ug 0 0 0 0 0 0 0 0 6 Vitamin C mg 20 2.4 7.4 9.6 0 0 22 8.6 60 Vitamin A IU 0 14187 0 10 0 0 0 5 900 Vitamin E mg 0.01 0.26 0.01 0.04 0.06 0.17 10.5 0.39 30 1Report #11352. One medium potato (2.25-3.25”) is about 213 g. One cup is about 150 g. 2Report #11507. One 5” sweet potato is about 130 g. One cup is about 133 g. 3Report #11833. Flesh boiled without skin. One medium potato of 2.25” is about 167 g. One cup is about 156 g. 4Report #11828. One medium potato (2.25-3.25”) is about 173 g. One cup is about 122 g. 5Report #20400. One cup elbow macaroni is about 140 g. 6Report #20037. One cup of long-grain brown rice is about 195 g. 7Report #19411. Serving size is 28 g (1 oz). Values given equal about 3 servings. 8Report #11403. All types. 10 French fries weigh about 76 g.

1.4.1.1 Starch and Resistant Starch

1.4.1.2 Content and Digestibility

Potatoes typically contain between 16-20% starch (Food and Agriculture Organization of the United Nations, 2008a) in the form of extensively branched amylopectin (70-80% of total starch), and more linear amylose (~20-30% of total starch) (Hoover, 2001). Potato starch is unique in the significant amounts of mono-phosphate esters covalently bound primarily to amylopectin (Hoover, 2001) resulting in a very high swelling power by provide repulsive forces within amylopectin chains, which allows water to more easily penetrate the structure (Ek et al., 2012). Additionally, a small percentage of potato starch is complexed with protein. Potato starch can provide unique functionality in food applications due to its high content of smooth medium (11-25 휇m) and large (>25 휇m) granules, high content of covalently linked phosphate, long amylopectin chains, and high-molecular-weight amylose (Bertoft and Blennow, 2009). It is commonly used as a thickener, stabilizer, gelling agent, bulking agent, or water-holding agent. Limitations include low shear and thermal resistance and high tendency to retrograde, however, starch modification can improve these properties (Singh et al., 2009). Native potato starch is classified as resistant starch, or starch that is undigested within 120 minutes of consumption but rather passes on to be fermented in the large intestine. Resistant starch can be classified as a type of dietary fiber and has demonstrated benefits for colonic health (Nugent, 2005). In 1992, Englyst and others classified resistant starch into three groups: RS1- physically entrapped starch; RS2- un-gelatinzed starch granules that are resistant to digestive action of amylases; and RS3- retrograded starch resulting from cooling after gelatinization. Now, another classification, RS4, exists to describe starches that have been chemically modified in a way that reduces digestibility (Sajilata et al., 2006). Native potato starch is characterized as RS2. It is crystalline in nature (B-type) and highly compact, which protects it from action by amylases and digestive enzymes. Extent of resistance is dependent on several factors including size, shape and porosity of the potato starch granule, extent of molecular association, amylose:amylopectin ratio, amylose chain length, and presence of amylose-lipid complexes (Ek et al., 2012; Hoover, 2001). Starches with B-type crystallinity have been found to be more resistant to

digestion than those with A-type crystallinity because enzymatic damage is confined to the surface of granules (Sajilata et al., 2006). Native potato starch has been found to be less digestible than other starches, such as maize, likely due to its high phosphorous and amylose content as well as the large size of the starch granules (Noda et al., 2008).

1.4.1.3 Effect of Processing

Upon cooking, starch in potatoes is gelatinized and converted to rapidly digestible starch (RDS), which means that it can be digested to glucose in 20 minutes or less (Englyst et al., 1992). The amount of RDS present in cooked potato products will largely determine glycemic response (Raigond et al., 2014). However gelatinized RDS present in cooked potatoes (especially amylose) has a tendency to retrograde upon cooling and become slowly digestible starch (SDS) or resistant to digestive enzymes (RS3 type) (Englyst and Cummings, 1987). While dietary fiber content is relatively low in potatoes, generation of resistant starch type RS3 through processing has been demonstrated to enhance dietary fiber content (Sajilata et al., 2006; Thed and Phillips, 1995). Therefore, method of preparation and consumption can have significant impacts on fiber content and glycemic response of potatoes (Slavin, 2013). Strategies to increase dietary fiber content and modulate glycemic response of potato products has been the subject of several investigations which will be discussed further in Sections 5.5 and 6.2.

1.4.1.4 Fiber

Recommendations of daily fiber intake are 25 and 38 g of fiber per day for women and men, respectively (Institute of Medicine, 2005). Potatoes contain approximately 1-2% dietary fiber by weight, which is concentrated in the peels. While potato cannot be considered a good source of fiber, a medium potato with skins can provide 3 g. At the level that potatoes are consumed in many diets, potato may provide a significant portion of dietary fiber (Kolasa, 1993). As stated in the previous section, processing can be used to enhance the dietary fiber content of potato products.

1.4.1.5 Sugars

In addition to starch, simple sugars are an important carbohydrate component of potatoes. Wilson, et al (1981) found that glucose is the sugar at greatest concentration in three varieties of potatoes, followed by fructose and sucrose, measured at both 3.3 and 7.2°C. However, Zhu, et al. (2010) reported that fructose had highest mean content in 16 varieties from Hong Kong, followed by sucrose, then glucose. Total sugar content can vary significantly between and within varieties, and even within a tuber (Watada and Kunkel, 1955). Amrein, et al. (2003) reported free sugar content of 17 varieties to range from 30- 1537 mg/kg and 97-2550 for glucose. Values for sugar content reported in these studies and throughout the literature range from <100 to >2000 mg/kg. Overall, concentration of sugars are highest in immature tubers and decrease over tuber development as starch synthesis is increased (Navarre et al., 2013; Payyavula et al., 2013). However, the starch to sugar ratio can be impacted by storage conditions (See sections 2.1 and 2.2). For example, cold induced sweetening of potatoes is a significant problem where potatoes stored at refrigerated temperatures undergo a biochemical conversion for starch to reducing sugars (Watada and Kunkel, 1955). This process has detrimental impact on finished processed products by promoting excessive brown color (Shallenberger et al., 1959) and acrylamide formation (Zhu et al., 2010). Currently strategies including biotech approaches are being leveraged to limit cold sweetening and enable refrigerated storage of potatoes for fresh market and processing (Sowokinos, 2001).

1.4.2 Protein

Potatoes contain between 2-2.5% protein, making them one of the richest protein source of any root or tuber crop (Food and Agriculture Organization of the United Nations, 2008a). In addition, because of its amino acid composition, potato protein is considered to be a very high quality plant protein source (Desborough et al., 1981; Kärenlampi and White, 2009). However, it is important to recognize that many other plant and animal foods contribute more protein to the diet than potatoes (Cotton et al., 2004). Potato proteins have been classified as patatins, protease inhibitors, and other proteins (Kärenlampi and White, 2009). Protein content, like other nutritional components in potatoes, decreases with maturity and is dependent on the cultivar/variety (Payyavula et al., 2013).

In general, potatoes are high in amino acids asparagine, glutamic acid, and aspartic acid, and low in methionine, cysteine, and histidine. Differences exist in amino acid content between varieties (Brierley et al., 1996; Zhu et al., 2010). However, the amino acid asparagine is most abundant in potatoes and has been positively correlated to acrylamide formation during potato frying (Zhu et al., 2010). Therefore, as with reducing sugars, interest in factors influencing free asparagine content have received significant attention. Amrein, et al. (2003) reported asparagine content from 17 potato cultivars grown in Switzerland ranged between 2010 and 4250 mg/kg FW. Interestingly, while varietal differences existed, there appeared to be little influence of farming system or extent of fertilization in this study (organic compared to conventional and integrated). Processing approaches to reduction of asparagine content include addition of asparaginase to convert asparagine to aspartic acid, yeast fermentation, lowering pH to protonate and/or partially hydrolyze asparagine, blanching, addition of glycine or lysine to compete with asparagine for binding, and addition of metal ions, among others (Friedman and Levin, 2008; Pedreschi et al., 2014). Agronomic approaches include limiting excess nitrogen during fertilization (asparagine is a nitrogen reservoir), choosing appropriate climate conditions, and of course breeding for selection of low asparagine content (Morales et al., 2008). More recently, transgenic approaches have been applied to the development not only of low reducing sugar tubers (Rommens et al., 2008) but reduction in free asparagine up to 95% (Rommens et al., 2006). In March of 2015 the FDA issued an evaluation of J.R. Simplot’s submission of potatoes genetically engineered to reduce levels of asparagine and reducing sugars. It was concluded that these genetically engineered potatoes are as safe for human consumption or feed as parent varieties (U.S. Food and Drug Administration, 2015)

1.4.3 Lipid

1.4.3.1 Natural Content

Potatoes have very little natural lipid, which comprises about 0.1% of fresh weight. The large majority (90%) of fatty acids in potato are palmitic, linoleic, and linolinic acids. Combined, polyunsaturated lipids make up approximately 70-76% of potato lipids. These lipids are mostly associated with lipoprotein membrane structures (Galliard, 1973). In contrast to other nutrients, lipid content in potato varieties does not widely vary. However, potato products often consumed have large amounts of added lipid, usually mono- and polyunsaturated oils, through frying or panfrying.

1.4.3.2 Lipid Addition through Processing

Processing potatoes by frying or roasting involves the addition of fat, which contributes additional energy and has potentially undesirable health effects. For example, relative to the low lipid levels in raw potatoes, commercial frozen French fries typically have about 15% lipid after final frying (Aguilera and Gloria-Hernandez, 2000). The French fry and chips industries have developed ways of reducing fat content, and uptake and retention of fat is often greater in home prepared, fried products compared to commercial fried products (Bradshaw and Ramsay, 2009). For example, home-fried chips had considerably more fat than commercial fried chips (40-45% compared to about 36%) (Burton, 1989, chap. 9). Studies suggest that oil absorption during frying is mainly a surface phenomenon and that most absorption occurs after the product is removed from the oil (Aguilera and Gloria-Hernandez, 2000; Bouchon et al., 2003). Between structural, penetrated surface, and surface fractions of oil, penetrated surface oil contributes the most to total oil content (Pedreschi et al., 2008). Strategies to reduce lipid content of potato products are discussed further in Section 6.1.

1.4.4 Vitamins

1.4.4.1 Content

Potatoes are a naturally good source of many vitamins, and high consumption rates make them a significant source of these vitamins in the US diet. Based on USDA nutrient data, a serving of whole, baked potato provides an excellent source (>20% of DV) of vitamin C and vitamin B6 and a good source (10-19% of DV) of niacin and folate (US Department of Agriculture Agricultural Research Service, 2014). A serving of potato equates to 1 cup of mashed/diced potato, or about one medium (2.5-3” diam.) boiled or baked potato (United States Department of Agriculture, 2015). However, content of vitamin C and other vitamins and nutrients have been shown to vary widely depending on potato variety, growing year or environment, and storage length (Augustin, 1975; Love et al., 2004; Singh et al., 2009). Folate analyzed in >70 potato cultivars varied between ~0.5 and 1.4 ug/100 g dw (Navarre et al., 2009). In general, vitamin C is lost over storage of potatoes, but reported levels vary. Dale et al. (2003) reported a two-fold difference in the average vit C. content between the highest and lowest vitamin C-containing varieties analyzed (n=33) and significant losses in content (35-55%) through storage for 4 months at 4°C. Mazza (1983) observed similar losses in Kennebec, Norchip, and Russet Burbank varieties over several months of storage. Linneman and others (1985) found that L-ascorbic acid (vit. C) content only decreased from 8.2 to 7.8 mg/100 g fresh weight in Bintje potatoes during 12 weeks of storage at 7°C (1985). Interestingly, they also discovered a slight increase in ascorbic acid content over 11 weeks of storage at 16°C. Tudela et al. (2002) reported a small increase in vit. C content in some varieties (Agria, Cara, Liseta, Monalisa) of potato strips stored in open air at 4°C for 6 days after cutting from long term-stored potatoes. However, vit. C in potatoes stored under frozen and modified atmosphere conditions decreased over the storage period. Lee and Kader (2000) discuss several pre-harvest, harvest, and post-harvest factors which affect vitamin C content in potatoes and other vegetables.

1.4.4.2 Effect of Processing

Studies have shown relatively high retention of vitamins in heat-processed potatoes. Augustin et al. (1978) measured retention of vitamin C, thiamin, riboflavin, niacin, folic

acid, and vitamin B6 in whole boiled, baked, and microwaved potatoes (R. Burbank, Katahdin, Norchip, and Pontiac). Discounting boiled peeled potatoes, retention (dry weight basis) of vitamin C ranged from 73-80%, thiamin 86-95%, riboflavin 77-87%, niacin 93-

103%, folic acid 71-88%, and vitamin B6 91-100%. Navarre et al. (2010) also reported 120- 140%, 116-122%, and 118-155% retention of vitamin C in Bintje, Piccolo, and Purple Majesty varieties, respectively, after microwaving, steaming, boiling, or baking. In a study by Golaszewska and Zalewski (2001), cooking methods without water resulted in 73-92% retention of vit. C. However, in other studies retention of vit. C and other vitamins through processing is low and/or varies depending on processing method (Keller et al., 1990). Han and others (2004) reported retention as low as 12-23% in boiled potatoes and as high as 67-79% in microwaved potatoes (ranges for Sumi, Chaju, and Dejima varieties). Lachman et al. (2013) measured retention of vit. C in Agria (yellow-fleshed), HB Red, Rote Emma (red- fleshed), Blaue St. Galler, Valfi, and Violette (purple-fleshed) potatoes. On average, boiled peeled potatoes retained 70% compared to fresh peeled, and microwaved and baked whole potatoes retained 66% and 38%, respectively, compared to whole fresh potatoes. In this study, peeling did not significantly affect vit. C content. In general, it appears that potatoes best retain vitamins after microwaving compared to other cooking methods. Vitamin C from processed potatoes has demonstrated similar bioavailability to that of water (Kondo et al., 2012).

1.4.5 Minerals

1.4.5.1 Content

Potatoes are an important source of many minerals, including (in order of percent contribution to DRI), copper (Cu), iodine (I), potassium (K), iron (Fe), phosphorous (P), manganese (Mn), magnesium (Mg), zinc (Zn), and calcium, (Ca) (Kärenlampi and White, 2009). When ordered by concentration, potatoes contain significant amounts of K, P, Mg, Ca, Fe, Zn, Mn, Zn (US Department of Agriculture Agricultural Research Service, 2014). Depending on soil and growing conditions, potatoes can also be a source of trace elements such as Se. Many minerals, such as Ca, K, Mg, Fe, and Mn are far more concentrated in the skin than the flesh, so peeling before processing reduces levels in finished products

(Wszelaki et al., 2005). Mineral content can vary widely among cultivars, depending on genetics and the environment in which the potato was grown (Ereifej et al., 1998; Rusinovci et al., 2012; True et al., 1979; White et al., 2009). In addition, complex mineral interactions within the soil and plant can impact mineral levels observed in different cultivars (White et al., 2009). Andre, et al. found the iron concentrations varied from 30-155 ug/g dw, calcium from 272-1093 ug/g dw, and zinc from 12.6-28.8 ug/g dw in 74 potato cultivars (2007a). Concentrations of minerals inside the potato seem to especially depend on the availability of minerals in the soil. Thus, the local soil composition as well as agronomic practices will affect mineral composition in potatoes. As overall productivity and yield increases, there is some concern that mineral content of commercial potatoes is decreasing as a results of dilution or depletion, however, this relationship has not been firmly established (Kärenlampi and White, 2009). Applying mineral fertilizers can increase mineral content, accelerate plant growth, and increase yield (White et al., 2009). Variation among cultivars also implies the potential for selective breeding to enhance mineral content of potatoes to address micronutrient deficiencies in the developed and developing world.

1.4.5.2 Effect of Processing

True et al. (1979) conducted a study in which three varieties of white potatoes were processed by four preparations: boiling with skin, without skin, oven baking, and microwaving. Few significant mineral losses were found in any mineral through any method of cooking in two of the three varieties. However, retention of minerals fell as low as 42% in the Norchip variety. In a variety of Irish Potatoes, boiling did not affect calcium levels, decreased magnesium levels, and actually increased iron levels compared to the raw form (Dilworth et al., 2007). Overall, processing does not seem to greatly effect mineral content, except by leaching and perhaps more so in some varieties than others.

1.4.5.3 Bioavailability

Human studies on the bioavailability of minerals from potatoes are limited. Information on the bioavailability of key shortfall nutrients including potassium, magnesium, calcium and iron has also been primarily limited to in vitro assays. Iron in vitro bioaccessibility was found to be generally lower than calcium and magnesium (Dilworth et

al., 2007). Using in vitro assays, Gahlalwal and Segal (1998) demonstrated that roasting or baking could enhance the availability of potatoes’ minerals. It is of interest to note that potatoes are high in compounds that improve absorption of minerals (such as Vitamin C), and low in phytate and oxalate, which limit absorption of minerals (Brown et al., 2005; Frossard et al., 2000). Phenolic compounds have also been shown to limit absorption of minerals, which should be taken into account when considering breeding high-phenolic varieties because this may reduce mineral bioavailability (Frossard et al., 2000). However, further human studies are needed to better understand the true contribution of potatoes to micronutrient status. This is particularly important for shortfall nutrients such as potassium, calcium and iron.

Potato Bioactive Phytochemicals Content and Bioavailability

In addition to their macro- and micronutrient content, potatoes are well known to be a source of several classes of dietary bioactive compounds, including phenolics, polyphenolics, polyamines, tocochromanols, carotenoids and glycoalkaloids (Table 4). The phytochemical content of potatoes has been the subject of several studies and also summarized in previous reviews (Brown, 2005; Camire et al., 2009; Ezekiel et al., 2013). Potatoes contribute significantly to dietary intake of phytochemicals, which are associated with several health benefits (Section 6).

1.5.1 Phenolic Acids and Flavonoids

Phenolics belong to a broad class of plant compounds structurally defined as containing one or more phenolic functional groups (Manach et al., 2004; Crozier et al., 2009). While thousands of individual phenolic species exist in nature, several broad classes have been defined based on specific structural conformations, oxidation states and/or substitution patterns including: simple phenolic acids, and complex polyphenols including stilbenoids, tannins and ellagitannins, lignans and flavonoids. Typically, flowers of the potato plant have much greater levels of phenolic acids than any other part, followed by leaves, stems, and then the tubers (Im et al., 2008). It is well-established that tuber skins consistently have greater concentrations of phenolics than the flesh. The most abundant

class of phenolic compounds in potato tubers are caffeoylquinic acids commonly known as chlorogenic acids (CGAs) which may account for up to 90% of the total amount of phenolic compounds in tubers (Payyavula et al., 2014). CGAs are synthesized in the potato through esterification of trans-cinnamic acids, primarily caffeic acid, with quinic acid (Stöckigt and Zenk, 1974). The most abundant CGAs in potato are 5-O-caffeoylquinic (5-CQA, chlorogenic acid) and its isomers 3- and 4-CQA known as, neochlorogenic and cryptochlorogenic acid, respectively (Andre et al., 2007b; del Mar Verde Méndez et al., 2004; Deusser et al., 2012; Im et al., 2008; Manach et al., 2004; Zhu et al., 2010). Free caffeic acid has been reported at significant levels in potatoes (<1-50 mg/100 g dw), however, the reported levels may depend on experiment methodology, as chlorogenic acid can be hydrolyzed to caffeic and quinic acid by acidic or alkaline conditions (Antolovich et al., 2000).

Table 4. Potato phytochemicals: Range of content of main phytochemicals in key commercial and select specialty varieties, grouped by phytochemical and potato flesh color.

Name Range1 Mean1 Potato Potato Flesh Number of Source Part (Skin) Color3 Varieties Chlorogenic Acid 2.6 23 7.2 Flesh2 W,Y (Y,R) 16 Deusser (2012) (5-Caffeoylquinic acid) 24 170 68 Whole W, Y 21 Navarre (2011) mw 354 39 85 11 Whole W (Bl,R,B) 4 Mendez (2004) 17 146 31 Whole W,Y (W,Y,P,R) 18 Andre (2007) 3.3 203 54 Whole W,Y (Y,B,R) 24 Im (2008) 42 318 138 Whole W,Y (Y,B,R) 8 Xu (2009) 42 219 89 Whole unk. 16 Zhu (2010) 22 231 74 Whole unk. 19 Navarre (2011) 44 1275 404 Whole R, P 5 Andre (2007) 383 383 Whole P 1 Deusser (2012) 80 330 230 Whole R, P 9 Navarre (2011) Cryptochlorogenic Acid 2.8 124 15 Whole W, Y 21 Navarre (2011) (4-Caffeoylquinic acid) 0.2 12 3.2 Flesh2 W,Y (Y,R) 16 Deusser (2012) mw 354 1.4 46 9.8 Whole W,Y (W,Y,P,R) 18 Andre (2007) 1 145 17 Whole unk. 19 Navarre (2011) 9.1 77 32 Whole R, P 5 Andre (2007) 13 64 39 Whole R, P 9 Navarre (2011) 428 428 Whole P 1 Deusser (2012) Neochlorogenic Acid 0.7 20 3.6 Whole W, Y 21 Navarre (2011) (3-Caffeoylquinic acid) 0.3 12 2.5 Flesh2 W,Y (Y,R) 16 Deusser (2012) mw 354 0.6 9.6 3.4 Whole W,Y (W,Y,P,R) 18 Andre (2007) 16 83 29 Whole unk. 16 Zhu (2010) 0.1 19 4.0 Whole unk. 19 Navarre (2011) 94 94 Whole P 1 Deusser (2012) 3.1 20 9.2 Whole R, P 5 Andre (2007) 2.9 44 24 Whole R, P 9 Navarre (2011) Caffeic Acid 0.02 0.07 0.04 Flesh2 W,Y (Y,R) 16 Deusser (2012) mw 179 0.5 14 6 Whole W, Y 21 Navarre (2011) 3.5 5.5 4.5 Whole W (Bl,R,B) 4 Mendez (2004) 0.5 15 6.7 Whole W,Y (Y,B,R) 24 Im (2008) 0.9 3.1 1.6 Whole unk. 16 Zhu (2010) 2 48 20 Whole unk. 19 Navarre (2011) 0.9 6.2 2.8 Whole W,Y (W,Y,P,R) 18 Andre (2007) 2.4 2.4 Whole P 1 Deusser (2012) 1.3 14 7.2 Whole R, P 5 Andre (2007) 5.2 15 10 Whole R, P 9 Navarre (2011) Ferulic Acid 0.02 0.06 0.03 Flesh2 W,Y (Y,R) 16 Deusser (2012) mw 194 0.5 4 2 Whole W (Bl,R,B) 4 Mendez (2004) 1 1 Whole P 1 Deusser (2012) p-Coumaric Acid n.d. n.d. n.d. Flesh2 W,Y (Y,R) 16 Deusser (2012) mw 164 n.d. 0.6 0.4 Whole W (Bl,R,B) 4 Mendez (2004) n.d. n.d. Whole P 1 Deusser (2012)

Name Range1 Mean1 Potato Potato Flesh Number of Source Part (Skin) Color3 Varieties Rutin n.d. 14 3.6 Whole W, Y 21 Navarre (2011) (Quercetin-3-rutinoside) n.d. 1.6 0.36 Flesh2 W,Y (Y,R) 16 Deusser (2012) mw 610 n.d. 19.1 4.6 Whole V 18 Andre (2007) n.d. 1.7 0.8 Whole unk. 19 Navarre (2011) n.d. n.d. Whole P 1 Deusser (2012) n.d. 16.6 4.9 Whole R, P 5 Andre (2007) 0.5 3.5 1.4 Whole R, P 9 Navarre (2011) Kaempferol-3-rutinoside n.d. 4.5 0.9 Whole W, Y 21 Navarre (2011) mw 594 n.d. 0.3 0.03 Flesh2 W,Y (Y,R) 16 Deusser (2012) n.d. 22.4 2.8 Whole W,Y (W,Y,P,R) 18 Andre (2007) n.d. 2.5 0.9 Whole unk. 19 Navarre (2011) n.d. n.d. Whole P 1 Deusser (2012) n.d. 22.7 6.1 Whole R, P 5 Andre (2007) n.d. 10.6 3.5 Whole R, P 9 Navarre (2011) Catechin n.d. 0.07 0.007 Flesh W,Y (Y,R) 16 Deusser (2012) mw 290 48.5 66 57 Whole W (Bl,R,B) 4 Mendez (2004) n.d. n.d. Whole P 1 Deusser (2012) Total Anthocyanins n.d. 54 33 Flesh W (P) 9 Lewis (1998) 1.4 5.2 3.8 Whole W,Y (W,Y,P,R) 5 Andre (2007) 2 46 18 Whole W,Y (P,R) 13 Jansen (2006) 15 1160 640 Flesh R, P 4 Lewis (1998) n.d. 1633 468.8 Whole R, P 5 Andre (2007) 42 785 238 Whole R, P 17 Jansen (2006)

1All units given in mg/100 g dw. If originally on ww basis, converted to dw using 80% moisture. 2Values for inner flesh and outer flesh were averaged 3W= White, Y= Yellow, R= Red, P=Purple, B=Brown/Tan, Bl= Black

Cyanidin Peonidin Petunidin

Malvidin Delphinidin Pelargonidin

Chlorogenic Acid caffeic acid quinic acid

5-O-caffeoylquinic acid (5-CQA) (chlorogenic acid)

Figure 1. Structures of primary phytochemicals found in Solanum tuberosum varieties. Top six structures illustrate anthocyanidin aglycones which are found as acylated glucosides in potatoes. Common epimers of chlorogenic acid (bottom) include 3-O-caffeoylquinic and 4-O-caffeoylquinic acids where caffeic acid is at the 3 or 4 position, respectively.

Flavonoids are a diverse subgroup of polyphenols characterized structurally by a 15 carbon (C6-C3-C6) flavan skeleton (Bravo, 1998; Beecher, 2003; Pietta, 2000). Flavonoids are subdivided into six major groups including anthocyanins, flavonols, flavan-3-ols (flavanols), flavanones, flavones and isoflavones (Beecher, 2003; Manach et al., 2004). In general, levels of flavonoids are lower in potatoes than those for phenolic acids and chlorogenic acids. However, appreciable levels (~0.6-21 mg total/100 g dw ) of flavonols, including quercetin-3-rutinoside (rutin), quercetin, myricetin, and kaempferol-3-rutinoside (Blessington et al., 2010; Lewis et al., 1998; Navarre et al., 2011; Payyavula et al., 2013) have been reported in certain potato varieties. Mendez, et al. (2004) quantified levels of the flavan-3-ol catechin in four varieties of potatoes from the Canary Islands. For these varieties, catechin levels (~48-66 mg/100g dw) were comparable to those of chlorogenic acid. Brown et al. (2005) and Reddivari et al. (2007) have also reported similar catechin levels in select potato varieties. However, generally, flavan-3-ols have not been routinely reported, or if reported, only at low levels in select varieties (Deusser et al., 2012; Navarre et al., 2011). In pigmented red and purple potatoes, anthocyanins are the primary flavonoid present. These flavonoid pigments provide red, purple to blue colors common to many flowering plants, vegetables and berries (Veitch and Grayer, 2008). In plants, anthocyanins exist almost exclusively as glycosides of anthocyanidins (defined as the aglycones) in acylated and non-acylated forms (Eichhorn and Winterhalter, 2005). Six main anthocyanindin forms in potatoes include: cyanidin, malvidin, delphinidin, peonidin, petunidin and pelargonidin (Del Rio et al., 2010, Brown, 2005). In purple varieties petunidin, malvidin, and peonidin derivatives are most common, while cyanidin and pelargonidin derivatives dominate in red-fleshed varieties (Brown et al., 2003; Eichhorn and Winterhalter, 2005; Payyavula et al., 2013). Anthocyanin content has been report up to 1600 mg/100 g dw in whole pigmented potatoes, but values range widely between varieties (Andre et al., 2007b; Jansen and Flamme, 2006; Lewis et al., 1998).

1.5.2 Carotenoids and Tocochromanols

Carotenoids are a class of lipid-soluble plant pigments that impart the bright yellow, orange, and red colors commonly seen in fruits and vegetables. While greater than 700 carotenoid species have been identified in nature, only six are commonly found in the

human diet and have been associated with health outcomes in humans (Maiani et al., 2009). These include lutein, zeaxanthin, - cryptoxanthin, -carotene, -carotene, and lycopene. Bright orange, red and yellow fruits and vegetables are often associated with having high carotenoid content. Orange-fleshed sweet potatoes have been reported to have a diverse range but generally high levels of carotenoids, mostly in the form of provitamin A - carotene. In a review by Bovell-Benjamin (2007) levels of -carotene were found to range between 4.5 mg/100g FW to upwards of 16,000 mg/100g FW. Biofortified orange sweet potatoes varieties have been reported to have levels reaching 79.1-128.5 mg/100 g DW (Donado-Pestana et al., 2012) . With such high levels of provitamin A carotenoids present in these tuber, it is not surprising that orange-fleshed sweet potatoes have become increasingly important in food security and nutritional intervention strategies for at risk populations in developing countries (Bovell-Benjamin, 2007). In contrast to orange-fleshed sweet potatoes, white- and yellow-fleshed and other colored (purple, red) Solanum tuberosum varieties do not typically accumulate high levels of carotenoids. In potatoes, non-provitamin xanthophyll carotenoids (lutein and zeaxanthin) predominate (Breithaupt and Bamedi, 2002; Payyavula et al., 2013). An analysis of 23 native Andean potato varieties of all colors, lutein, zeaxanthin, neoxanthin, violaxanthin, and antheraxanthin were the most common carotenoids, followed by beta-cryptoxanthin and beta-carotene at minor levels of <1 mg/100 g dw (Andre et al., 2007b). Tocochromanols are a class of eight related compounds that collectively contribute to Vitamin E content in foods. These include four tocopherols (, and ) and four tocotrienols (, and ), which differ structurally by the position and number of methyl groups on the chromanol ring (Dörmann, 2007). Potatoes are not considered to be a rich source of tocochromanols (Chun et al., 2006). In studying oxidative damage to potatoes through low temperature storage, Spychalla and Desbourogh (1990) reported a-tocopherol contents ranging between 13 and 29 ug/100g FW. Similarly, Andre et al (2007) reported that typical potato varieties contain about 0.7-4.5 ug/g fresh weight of alpha-tocopherol, although some wild Andean varieties contain up to 21 ug/g dry weight. Only alpha- tocopherol, not beta- or gamma-tocopherol, was identified in these varieties (Andre et al., 2007b). While the potato itself is not considered a good source of vitamin E, potato products often have higher levels of tocochromanols by virtue of the oils in which they are prepared.

Vegetable oils are a rich source of tocochromanols (Falk and Munné-Bosch, 2010). During frying, potatoes can absorb significant amounts of oils and by extension the tocochromanols that these oils possess (Fillion and Henry, 1998). Tocopherols can deteriorate through frying operations, leading to changes in both tocopherol and lipid profiles (Gordon and Kourkimskå, 1995; Rossi et al., 2007). Andrikopoulos et al. (2002) reported significant retention of these compounds has been reported through up to eight frying uses, typical of household preparation. However, while susceptible to oxidation during frying, tocopherols from vegetable oils can provide some measure of oxidative stability to finished products (Ruiz et al., 1999).

1.5.3 Glycoalkaloids

As with other members of the nightshade family, potatoes produce glycoalkaloids that function as phytoalexins protecting tubers from infections but also possess potentially toxic effects in humans. In potatoes two main a-solanine and a-chaconine predominate with minor forms including leptine, demissine and leptinine also found in potatoes tubers primarily accumulating the peels of potatoes (Friedman, 2006). Historically viewed as potentially toxic compounds, potato glycoalkaloids, when consumed at high levels (>3-10 mg) have been documented to produce neurotoxic effects through inhibition of cholinesterase activity (Bushway et al., 1987) and proinflammatory effects in the GI and other tissues through disruption of cell membrane integrity, specifically cholesterol containing cell membranes (Keukens et al., 1992). However, at lower levels these compounds have also demonstrated the potential to promote anti-inflammatory responses (Kenny et al., 2013) and anti-cancer effects primarily through disruption of cellular membranes of cancer cells (Lee et al., 2004). The extent to which adverse health effects could be attributed to glycoalkaloid intake as part of a normal diet containing potatoes is not clear. Regardless, significant efforts have been made to mitigate levels of these potentially toxic compounds in potatoes. New commercial potato cultivars should have glycoalkaloid levels below 20mg/100g fw (~1 mg/g dw) to meet recommended safety guidelines (Friedman et al., 1997). Most commercial varieties evaluated have levels below this mark, but some primitive germplasm and wild-species have much higher levels. Glykoalkaloids other than solanine and chaconine contribute to these high levels (Navarre et al., 2011). Glycoalkaloids also appear

to decrease in concentration over tuber maturation (Papathanasiou et al., 1998; Payyavula et al., 2013). The higher glycoalkaloid content of younger potatoes could be a potential limiting factor in the commercial use of immature potatoes. Peeling significantly reduces glycoalkaloid content (by ~75%) (Mäder et al., 2009), and blanching also significantly reduces glycoalkaloid content via leaching. Glycoalkaloids are reported to be relatively stable to heating, so further heat processing appears to have little effect on glycoalkaloid concentration (Mäder et al., 2009).

1.5.4 Factors Impacting Phytochemical Content in Potatoes and Potato Products

1.5.4.1 Natural Variation

As with diversity in other fruits and vegetables, phytochemical content can differ widely among potatoes varieties. Blessington et al. (2010) found that genotype influenced levels of 80% and 50% of phenolic acids and flavonoids, respectively. Overall, purple and pink-fleshed potatoes have higher concentrations of phenolics than yellow and white- fleshed varieties, and these differences are often dramatic (Payyavula et al., 2013). Navarre, et al. (2011) conducted a study on 50 varieties of potatoes, including colored-, yellow-, and white-fleshed potatoes, and found a 6-fold difference in content of total phenolics between the lowest (~170 mg/100g R. Burbank) and highest (~950 mg/100g Magic Molly) varieties. As previously stated, similar diversity can be observed with carotenoid content in both orange and other colored potatoes varieties (Bovell-Benjamin, 2007). Much of this diversity is a result of centuries of breeding for traits such as color, texture and flavor. More recent efforts to increase the content of select nutritive phytochemcials including carotenoids (Ducreux et al., 2005) and tocopherols (Crowell et al., 2007) continue to add to this available variety.

1.5.4.2 Effect of Environment/Storage

Location of growth may impact phytochemical content. Researchers found that Colorado tubers had higher levels of anthocyanins when compared to the same tubers grown in Texas, while the tubers grown in Texas grew slightly larger than those grown in

Colorado. These differences could be explained by cooler temperatures, yet longer days (more solar radiation) in Colorado. Phenolic acid content did not significantly differ between locations (Reyes et al., 2004). Research also indicates that wounding treatment, light, and temperature can affect levels of polyphenols in potatoes during storage, though content and effects can vary widely among cultivars. Petersson, et al.(2013) show that wounding and light treatment both increased glycoalkaloid content in 21 tuber varieties, but heat treatment did not. Tudela et al.(2002), demonstrated significant flavonol and caffeic acid derivative accumulation in fresh cut potatoes after 6 days of storage. Accumulation was greater in the light than in the dark. Some research indicates that long-term stored fresh potatoes have greater amounts of phenolic compounds than short-term stored or non-stored fresh potatoes, though effects vary depending on compounds analyzed and type of storage treatment (Blessington et al., 2010; Juan A. Tudela et al., 2002).

1.5.4.3 Effect of Maturity and Plant Part

Immature potatoes, or “new potatoes” are often reported to have greater amounts phytochemicals and vitamins, and in general concentration of these compounds per unit weight decreases as the tubers mature. The percent decrease at final maturity varies widely and seems to be influenced by variety type and growing conditions (Navarre et al., 2011; Payyavula et al., 2013; Reyes et al., 2004). Reyes, et al. (2004) discovered that for three varieties of purple-fleshed potatoes grown in both Texas and Colorado, the decrease in anthocyanins through maturation (ranged from 19-57%) was greater than the decrease in phenolic acids through maturation (ranged from 1-29%). However, total yield of phenolics and anthocyanins in this study was greater at later maturity stages because the size of each tuber was greater.

1.5.4.4 Effect of Processing

In recent decades, several authors have demonstrated decreases in phytochemicals and antioxidants through processing, though degree of degradation varied widely (See Table 5). For example, Im, et al. (2008) investigated the effect of several types of processing on phenolics in the Superior potato variety. Potatoes were boiled with 1% salt, boiled with

3% salt, oven heated, steam heated, microwaved, sautéed, and fried. Results indicate that chlorogenic acid was best retained via oven heating, and that most all the processing methods had between ~60-80% retention of chlorogenic acid. Maeder et al. (2009) suggest that decreases in chlorogenic acid during processing could occur through isomerization to neochlorogenic acid. Though they found that cryptochlorogenic acid levels remained relatively stable during processing, this may actually be a result of simultaneous degradation and formation from isomerization, rather than truly static levels. However, more recently, evidence has emerged suggesting that polyphenols do not always decrease during processing, and may actually increase. Deusser and others (2012) demonstrated that boiling did not significantly affect chlorogenic and ferulic acid or rutin levels, but the levels of neochlorogenic and cryptochlorogenic acids, vanillin, and catechin were increased. Navarre et al. (2010) also noticed marked increases in content of chlorogenic acids as well as flavonols and Vitamin C after boiling, microwaving, steaming, or baking, which they do not attribute to enhanced extractability of these compounds post- processing. It is notable that these authors endeavored to apply the gentlest process possible while still fully cooking the potato, which may partially explain the greater levels of phytochemicals post-processing compared to those found by most other authors. In addition, the authors suggest that inactivation of degradative enzymes through heating could improve polyphenol content. It appears that processing may affect phenolic compounds differently. Blessington et al. (2010) found that average levels of phenolic acids, including 5-O-CQA and caffeic, vanillic, and p-coumaric acids, and epicatechin actually increased, while levels of quercetin dehydrate decreased. Total carotenoids in this study did not change through processing, except a slight decrease after boiling. Jaarsveld et al. (2006) also observed high retention (70-90%) of beta-carotene in sweet potatoes through boiling. Some research has been conducted on the process stability of anthocyanins in various foods (Patras et al., 2010), though studies specific to potato appear to remain limited to storage, rather than processing, conditions. In regards to other vegetables, Volden et al. (2008) observed that blanching, boiling, and steaming reduced total monomeric anthocyanins in purple cabbage by 59, 41, and 29% respectively. Kirca et al. (2007) found that black carrot anthocyanins (45 Brix, pH 4.3) had a half-life of 14.8, 6.9, and 3.2 hours when held at 70, 80, and 90°C, respectively. These authors postulate that the

relatively high stability of carrot anthocyanins during heating could be due to their acylated form (Giusti and Wrolstad, 1996). Because pigmented potatoes also contain primarily acylated anthocyanins (Giusti and Wrolstad, 2003; Rodriguez-Saona et al., 1998), their anthocyanins, like those of black carrot, may also be relatively stable. Some research does point to the potential for an increase in antioxidant capacity with certain types of cooking (Pellegrini et al., 2009). In a study conducted by Navarre et al. (2010), Trolox equivalent antioxidant capacity increased or stayed the same in two varieties of potatoes after microwaving, steaming, boiling, and baking. Retention ranged from 101-174% in whole processed potatoes compared to raw whole potatoes. However, Xu et al. (2009) found that boiling, baking, and microwaving decreased ORAC values in 8 varieties of potatoes, with retention ranging from 68-97% depending on variety and cooking method. Here, the differences in measurement must also be considered. While various forms of phytochemicals have traditionally been viewed as highly susceptible to degradation through heating, some results suggest that when the process is minimized, levels of phytochemicals and antioxidants may be unaffected, or may be altered physically or chemically in a manner that facilitates their ability to act as an antioxidant. However, it seems that the observed effect of processing on phytochemicals may vary more based on research method than on the processing method or type of potato. More research is needed which controls for the high natural variation in potatoes as well as potential changes in extractability with processing to understand these disparate results.

Table 5. Effects of several processing methods on potato phytochemical content, grouped by processing type and author.

Processing Effect of Approx. Processing Methods Potato Part Varieties Polyphenol(s)/Nutrients Source Type Processing1 Retention2

Whole potato steam 55% from raw Maeder Peeling Flesh Karlena Sum of phenolics by HPLC peeled 9 sec @220°C whole (2009) Whole potato boiled 18 Whole Total phenolics, CGA, NCGA, CCGA, 100-300% from Navarre Boiling Purple Majesty, Piccolo, Bintje min (New Potato) Rutin, Kaempferol, Vit C. raw whole (2010)

100-110% from Whole potato boiled, CGA, ferulic acid, rutin raw flesh Deusser then flesh and peel Flesh Bintje caffeic acid, NCGA, CCGA, catechin, 600-900% from (2012)

separated 35 vanillin raw flesh

HB Red, Rote Emma, Blaue St. 60-120% from Lachman Flesh boiled 15 min Flesh chlorogenic acid Galler, Valfi, Violette, Agria raw flesh (2013) CGA, caffeic acid, vanillic acid, p- 106-300% from Atlantic, ATX85404-8W, Innovator, Potato dices (with peel) coumaric acid, epicatechin raw whole Blessington

Whole Krantz, NDTX4930-W, R. Burbank, boiled 25 min 40% from raw (2010) Santana, Shepody quercetin dihydrate whole

Slices blanched 20 min @ 90% from raw Maeder Flesh Karlena Sum of phenolics by HPLC 70°C flesh (2009)

Strips boiled for 1.5 min Quercetin derivatives, caffeic acid 33-50% from Tudela Flesh Monalisa in pressure cooker derivatives raw flesh (2002)

Whole potato boiled 30 40% from raw Whole NDA 1725 CGA Dao (1992) min whole

58-95% from Dakota Pearl, Goldrosh, Nordonna, Total phenolics (Folin) Whole potato boiled 15 raw whole Whole Norkotah, Red Norland, Sangre, Xu (2009) min 30-360% from Viking, Dark Red Norland CGA, CCGA, NCGA raw whole

60-70% from Plugs boiled 10 min Whole Superior CGA, CGA isomer (unidentified) Im (2008) raw whole Whole potatoes boiled 18 caffeic, ferulic, sinapic, vanillic, p- 90-140% from Mattila Peel Van Gogh, Rosamund, Nicola min coumaric, syringic raw peel (2007) Whole potato steamed Whole Total phenolics, CGA, NCGA, CCGA, 90-300% from Navarre Steam Cooking Purple Majesty, Piccolo, Bintje 15 min (New Potato) Rutin, Kaempferol, Vit C. raw whole (2010)

Slices steam cooked 30 80% from raw Maeder Flesh Karlena Sum of phenolics by HPLC min @ 100°C flesh (2009)

Strips steamed 2 min in Quercetin derivatives, caffeic acid 55% from raw Tudela Flesh Monalisa pressure cooker derivatives flesh (2002) Plugs cooked 10 min in 50-60% from Whole Superior CGA, CGA isomer (unidentified) Im (2008) steam cooker raw whole Whole potato Whole Total phenolics, CGA, NCGA, CCGA, 90-130% from Navarre Microwaving Purple Majesty, Piccolo, Bintje microwaved 2.5 min (New Potato) Rutin, Kaempferol, Vit C. raw whole (2010)

Whole potato cubes HB Red, Rote Emma, Blaue St. 15-50% from Lachman Whole chlorogenic acid microwaved 10 min Galler, Valfi, Violette, Agria raw whole (2013) CGA, caffeic acid, vanillic acid, p- 116-675% from Atlantic, ATX85404-8W, Innovator, Potato dices (with peel) coumaric acid, epicatechin raw whole Blessington Whole Krantz, NDTX4930-W, R. Burbank, microwaved 2.5 min 30% from raw (2010) Santana, Shepody quercetin dihydrate whole

Plugs cooked for 1 min on 65-80% from Whole Superior CGA, CGA isomer (unidentified) Im (2008) high heat raw whole

Whole microwaved 30 54% from raw Whole NDA 1725 CGA Dao (1992) min @ 218°C whole Quercetin derivatives, caffeic acid 28-42% from Tudela Strips microwavved 4 min Flesh Monalisa derivatives raw flesh (2002)

61-95% from Dakota Pearl, Goldrosh, Nordonna, Total phenolics (Folin) Whole potato raw whole Whole Norkotah, Red Norland, Sangre, Xu (2009) microwaved 5 min 5-147% from Viking, Dark Red Norland CGA, CCGA, NCGA raw whole Whole potato baked 30 Whole Total phenolics, CGA, NCGA, CCGA, 92-250% from Navarre Baking Purple Majesty, Piccolo, Bintje min @ 350°C (New Potato) Rutin, Kaempferol, Vit C. raw whole (2010)

Baked, hot air oven, 45 HB Red, Rote Emma, Blaue St. 20-80% from Lachman Flesh chlorogenic acid min @ °C Galler, Valfi, Violette, Agria raw whole (2013) CGA, caffeic acid, vanillic acid, p- 110-440% from Potato dices (with peel) Atlantic, ATX85404-8W, Innovator, coumaric acid, epicatechin raw whole Blessington microwaved 15 min @ Whole Krantz, NDTX4930-W, R. Burbank, 40% from raw (2010) 204°C Santana, Shepody quercetin dihydrate whole

Whole baked 45 min @ 0% from raw Whole NDA 1725 CGA Dao (1992) 212°C whole

Plugs baked in foil 10 min 80-95% from Whole Superior CGA, CGA isomer (unidentified) Im (2008) @ 200°C raw whole

70-99% from Dakota Pearl, Goldrosh, Nordonna, Total phenolics (Folin) Whole tubers baked 40 raw whole Whole Norkotah, Red Norland, Sangre, Xu (2009) min @ 178°C 4-465% from Viking, Dark Red Norland CGA, CCGA, NCGA raw whole CGA, caffeic acid, vanillic acid, 100-575% from Frying Potato dices (with peel) Atlantic, ATX85404-8W, Innovator, p-coumaric acid, epicatechin raw whole Blessington fried in tea balls 1 min @ Whole Krantz, NDTX4930-W, R. Burbank, 20% from raw (2010) 191°C Santana, Shepody quercetin dihydrate whole

Plugs boiled for 7 min, 75-85% from fried 30 sec twice @ Whole Superior CGA, CGA isomer (unidentified) Im (2008) raw whole 170°C

Frozen French fries Flesh Unk. CGA 0 mg/100 g dw Dao (1992)

Strips fried 4 min @ Quercetin derivatives, caffeic acid 28-45% from Tudela Flesh Monalisa 190°C derivatives raw flesh (2002)

Panfrying/ Pieces sautéed in pan 3 65-80% from Whole Superior CGA, CGA isomer (unidentified) Im (2008) Sautéeing min raw whole

Mashed slices drum dried 80% from raw Maeder Drying Flesh Karlena Sum of phenolics by HPLC @ 160°C flesh (2009)

1Shapes represent general increase, decrease, or no change in potato phytochemical based on retention from flesh 2Retention reported or calculated by [amount remaining in processed sample/original amount in raw flesh or whole]

1.5.5 Bioavailability of Phytochemicals in Potatoes

In addition to providing nutrients, potatoes may serve as a unique matrix to delivery bioactive phytochemicals. While the bioavailability of carotenoids and phenolics from plant foods has been the subject of intense investigation (reviewed by Crozier et al., 2009; Del Rio et al., 2010; Ferruzzi, 2010; Manach et al., 2005b, 2004; McGhie and Walton, 2007; Neilson and Ferruzzi, 2011) much less is known regarding availability of potato derived phytochemicals. The process of phytochemical absorption is complex and involves both pre- absorptive and absorptive events that ultimately determine the site and extent of absorption as well as circulating forms and tissue profiles. Interactions in the gut with macronutrients and micronutrients and the availability of these phytochemicals for absorption and reaction is a critical component to the health benefits potentially derived from potatoes. Focusing on food matrix and gut specific pathways, the overall absorptive process can be compartmentalized to include (1) release and solubilization of the phytochemical in the gut during digestion followed by (2) intestinal absorption/metabolism and (3) entrance into circulation and further tissue distribution prior to (4) final elimination (Neilson and Ferruzzi, 2011). Differences exist depending on the nature of the phytochemical (lipid versus water soluble) as well as affinity for transporters (active versus passive transport). This is summarized in Figure 2 and described in more detail for potato phenolics and carotenoids.

Potato Phytochemicals

Fat soluble Water soluble Carotenoids (CRT) Phenolic acids (PA) Tocopherols (TOC) Chlorogenic Acid (CGA) Flavonoids (FLA) Blood Lipid (TAG) Lympha c Hepa c/portal Circula on Enterocyte Enterocyte Circula on Stomach circula on

Ini al Release From food matrix CGA Ac ve CRT PA FLA FLA TOC FLA Starch Solubilized Diges on in bulk oil a-amylase

Lipid Diges on

Small intes ne Ac ve Transport Glu Glu Transfer to CGA FFA Bile salt lipid CGA CGA MAG micelles PA Passive PA PA FLA transport FLA CRT CRT CRT FLA TOC TOC TOC Further release by diges on Chylomicron Metabolism CRT Synthesis CRT CRT PP-M TOC Packaging TOC Chylomicron TOC PP-M PP-M Secre on

Colon Microbiota CGA, PA FLA Microbial CRT Metabolism TOC PP-CM PA PP-CM

Feces Figure 2. Overview of the digestion and intestinal absorption of phytochemical from potatoes. Both lipid soluble and water soluble phytochemicals require initial release from the food matrix by digestion and solubilization either in bulk oil or aqueous continuous phase of chime in the gut. This digestive release is dependent on specific association in the food matrix between phytochemcials and macronutrients (starch, protein and lipid). Lipid soluble carotenoids and tocopherols released from potato matrix associate initially in bulk oil during initial oral and gastric processing. Subsequent digestion of the oil in the small intestine facilitates partitioning of carotenoids and tocopherols to bile salt lipid micelles. Similarly, phenolics associated with starch and protein in the potato matrix must be released by digestion in the stomach and small intestine. Intestinal absorption of can then be mediated by both passive diffusion and active/facilitated processes involving transporters such as SCRB1 (carotenoids) and MCT and GLUT2 (phenolics). Active/facilitate transport may be modulated by presence of macronutrients released during digestion (fatty acids and glucose). Once internalized in the enterocyte, phytochemicals can be metabolized prior to their transport/secretion into circulation and further metabolism (hepatic) or tissue distribution and excretion. Unabsorbed phytochemicals would be made available for metabolism by gut microbiota. (Adapted from mechanism described by Neilson and Ferruzzi, 2011).

1.5.5.1 Bioavailability of Potato Polyphenols

The bioavailability of chlorogenic acid and anthocyanins from foods can be categorized as modest to very poor, respectively. While approximately one third of ingested chlorogenic acid has been reported to be absorbed in the small intestine following a supplemental dose (Olthof et al., 2001), anthocyanin bioavailability is substantially lower- typically ranging below 2% in many animal and human studies (Faria et al., 2013). In addition, bioavailability of acylated anthocyanins, the primary forms found in pigmented potatoes, is thought to be lower than that of non-acylated anthocyanins (Kurilich et al., 2005). For chlorogenic acid, significant bioavailability research has been reported for other matrices such as coffee. Between 10-30% absorption has been observed when including both free and metabolized chlorogenic acid in circulation (Erk et al., 2012; Farah et al., 2008; Stalmach et al., 2014). While in vivo studies are limited with potatoes, evidence of phenolic absorption from sweet potato tubers (Ipomoea batatas) confirms absorption of both phenolics in animals and humans (Harada et al., 2004; Oki et al., 2006; Suda et al., 2002). Generally absorption of anthocyanins was observed to be rapid with Tmax values of 30min or less and modest Cmax values only in the nM range. These results are consistent with those reported for other phenolics from other plant food matrices. Similar findings were observed using an in vitro model to assess the bioaccessibility of phenolics from various potato varieties. Miranda, et al. (2013) observed that polyphenols in potatoes and sweet potatoes are released during the gastric and small intestinal digestion phase, but only modestly absorbed (0.1-0.9%) by Caco-2 human intestinal cells. These results suggest that release from the food matrix may not be a limiting factor for potato phenolics, but consistent with other food matrices, intestinal transport and metabolism likely remain the rate limiting step (Neilson and Ferruzzi, 2011). One factor to consider regarding potato phenolics is the potential for direct and indirect interactions between potato starch and endogenous phenolics. The presence of carbohydrate in a food matrix either as simple sugars or digestible starch have demonstrated the ability to enhance flavonoid absorption in both humans (Cohen et al., 2011; Schramm et al., 2003) and animal models (Neilson et al., 2010; Peters et al., 2010). This impact is believed to be due both to pre-absorptive increases in flavonoid solubility and to interaction with specific absorptive mechanisms at the intestinal level likely including competitive interactions with glucose transporters, notably SGLT1 and GLUT 2

(Farrell et al., 2013). The extent to which potato starch may serve to enhance bioavailability of chlorogenic acid, anthocyanins or other phenolics remains to be investigated in detail.

1.5.5.2 Bioavailability of Potato Carotenoids

As with phenolics, absorption of lipid soluble carotenoids is a complex, multistep process that is dependent on including: 1) Digestion and release from the food matrix, 2) Solubilization in the gut lumen by transfer into bile-salt lipid micelles, 3) Transport into intestinal epithelial cells, and 4) Incorporation into chylomicrons and secretion into the lymphatic system (Goltz and Ferruzzi, 2013). This process is highly aligned with and dependent on consumption of lipid in the form of triacylglycerides to potentiate carotenoid and tocopherol micellarization (Reboul et al., 2006) and intestinal secretion with chylomicron (Goltz and Ferruzzi, 2013). Considering the low natural level of lipid in potatoes, it becomes critical to consider final product form and formulations including inclusion of fat as a cooking medium (frying), in the product formulation, or in the context of the full meal. Similar to the body of evidence available for potato phenolics, very little work has been done on absorption of carotenoids and tocopherol from potatoes (S. tuberosum ) but significantly more has been done with sweet potato (Ipomoea batatas). Therefore both will be discussed in the context of this review. In one of the few reports on carotenoid bioaccessibility, Burgos et al. (2013) reported in vitro digestive recovery (70-95%) and relative bioaccessibility (33-71%) of lutein and zeanxanthin from yellow fleshed potatoes. These values are similar to those reported for typical salad vegetables (Failla et al., 2014; Huo et al., 2007) and select thermally processed foods (Garrett et al., 2000; Kean et al., 2008; Reboul et al., 2006). While modest compared to dark green vegetables (Vinha et al., 2015) this level of bioaccessibility can provide up to 600 ug/100g serving of boiled potatoes (Burgos et al., 2013). Significantly more is known regarding orange flesh sweet potato as a food vehicle for vitamin A (through provitamin A carotenoids) (Berni et al., 2015; Failla et al., 2009; Mills et al., 2009). Bioaccessibility of b-carotene from orange fleshed sweet potato was reported to be low (0.6-3.0%) (Failla et al., 2009). This low level is in fact consistent with low bioaccessibility for carotenes relative to xanthophylls (Huo et al., 2007). Leveraging lipid in

product formulation is known to enhance carotenoid bioaccessibility and absorption in vivo (Mills et al., 2009). Bengtsson et al. (2009) further reported that heat processing and lipid addition (2.5%) could enhance b-carotene in vitro bioaccessibility up to 22% from orange fleshed sweet potatoes In humans, deep frying sweet potato was reported to provided a higher relative serum response of b-carotene compared to green leafy vegetables but significantly lower than supplemental doses (Huang et al., 2000). Considering the similarities between potato tubers and sweet potatoes, it is logical to assume similar effects from processing of sweet potatoes would be applicable to carotenoids from yellow and orange fleshed potatoes. However, these effects must be assessed directly.

Health Benefits of Potatoes and Potato Products

Potatoes hold a confusing and often controversial role in human health and nutrition. While potatoes play a critical role in food security, they are simultaneously associated with the shortcomings of the Western diet by being associated with high fat, salt and glycemic index. Interestingly, studies suggest both positive and negative effects on energy balance and chronic disease risk are associated with potato consumption. These effects are clearly associated with the nature of the potato processing and in home preparation, which can greatly impact final nutritional quality, and to a larger extent, the nature of the foods potatoes are often consumed with. Reviews by Camire (2009) and King and Slavin (2013) have previously discussed potatoes and human health with a focus on the potatoes overall, and, to a more limited extent, commonly consumed products. The following sections address primarily the potential positive nutritional impacts of potatoes and the potential for potato products to leverage this value.

1.6.1 Contribution to Dietary Nutrients of Concern and Bioactive Compounds

As previously described, potatoes of all forms and colors remain an important source of nutrients and bioactive phytochemicals in the diet. Table 5 highlights that for US adults, white potato ranks in the top 15 contributors among 112 foods/food groups for 15 key nutrients (out of 30 total). This includes key shortfall nutrients including potassium and fiber (2015 Dietary Guidelines Advisory Committee, 2015). By more recent NHANES

(National Health and Nutrition Examination Survey) data (2009-10), potatoes provided 12.9-24.9% of daily potassium intake and 14.4-26.2% of daily fiber intake for US men and women. Overall, this is a result of both the nutrient content and the relatively high consumption of potato products by the population. NHANES data reveals that average intake of white potatoes from 24-hour recall varied between age groups (highest for 19-30 year old women and 51-70 year old men), but was between 37.9-54.6 g/day for men and 30.0-40.8 g/day for women. French-fried potato products provided additional potato intake of 3.5-16.0 g/day for men and 1.4-18.5 g/day for women. When compared to other vegetables, potatoes and French-fried potatoes together comprised about 30% of total vegetable intake for men and 27% for women (Storey and Anderson, 2013).

Table 6. Percent of dietary nutrient provided by potato for US adults (1994-96) and rank among 112 food/food groups (Cotton et al., 2004).

White Potato2 Potato chips/corn Sweet Potato2 chips/popcorn2 Nutrient1 % Rank % Rank % Rank Energy 2.8 10 2.5 15 -- -- Carbohydrate 5.3 5 2.3 14 -- -- Protein 1 15 ------Total Fat -- -- 3.9 10 -- -- Fiber 7.5 3 3.6 7 -- -- Vitamin C 5.8 5 ------Vitamin E -- -- 3.4 9 -- -- Vitamin A (IU) ------4.6 5 Folate 2.9 7 1 <20 -- -- Thiamin 3.8 9 ------Riboflavin -- -- 1 <20 -- -- Niacin 3.9 5 1 <20 -- -- Vitamin B6 8.5 4 2.1 11 -- -- Phosphorus 2.8 8 1 16 -- -- Sodium -- -- 1 14 -- -- Potassium 8.9 2 2.3 11 -- -- Iron 2.6 9 1 19 -- -- Zinc 1 13 1 19 -- -- Magnesium 4.7 5 11 2.8 -- -- Copper 8.5 1 1 <20 -- -- 130 nutrients were assessed. Nutrients that no potato product significantly contributes to (at least 1%) were not included. These are cholesterol, vitamin B12, calcium, and selenium. 2Blank spaces indicate that the potato provided <1% of the nutrient to the diet and had low ranking.

In line with the previous discussion of potato phytochemicals, potato products are often overlooked as significant dietary sources of bioactives. White potatoes, while relatively low in polyphenols compared to fruit and green vegetables (Brat et al., 2006), contribute significantly to overall dietary polyphenols due to overall consumption. In France, potato polyphenols account for about 45% of total polyphenol intake- more than any other vegetable (Brat et al., 2006). In the United States, potatoes follow only oranges and apples in contribution to phenolic intake among commonly consumed fruits and vegetables (Chun et al., 2005). More recent estimates suggest that potatoes may account for ~25% of the phenolics in the American diet highlighting just how overlooked these products may be in terms of contribution of dietary bioactive components (Liu, 2013). While typical white- and yellow-fleshed potatoes are most commonly consumed, colored- flesh varieties are potentially impactful as a significant source of phytochemicals, relative to all vegetables consumed (Navarre et al., 2011). Shifts in consumption towards more phytochemical-rich varieties could have significant impact in the overall nutrient density of these foods. There is an opportunity for potato to serve as carriers for phytochemicals that have been associated with prevention of several chronic and degenerative diseases. Furthermore, evidence has accumulated that phytochemicals, such as phenolics and polyphenols, may alter nutritional functionality of foods by virtue of interactions with macronutrients (reviewed by Bordenave et al. 2015) suggesting that these non-nutritive components may play a significant role in the nutritional quality of potato products and merit further discussion and investigation.

1.6.2 Potatoes and Risk of Chronic Diseases

Potato consumption has often been associated with elevated risk of certain chronic diseases, most notably, type 2 diabetes (Halton et al., 2006; Khosravi-Boroujeni et al., 2012) and colon cancer (Miller et al., 2010). For diabetes, the association is often attributed to the high starch content of potatoes and high glycemic response induced by many forms of cooked potatoes. Further, addition of ingredients such as fat and sodium (in fried products) that have been associated with negative health outcomes (Shikany and White Jr., 2000) or consumption with red meats and other “high risk foods” has made for a complex mixed message on the nutritional value of potato products. Several potential health benefits of potato consumption have been previously reviewed. This includes prevention of cancer,

cardiovascular disease, and obesity (Camire et al., 2009; McGill et al., 2013). Generally, while associations have been made, both positive and negative, much remains to be studied, as consistency in reporting of potato forms and other potential confounding factors, including context of potato consumption in the overall diet, remains limited. Still, many of the potential benefits are believed to be due to the combination of macro and micronutrients as well actions promoted by potatoes bioactives including phenolic and carotenoids (Liu, 2013). As a key dietary source of potassium, vitamin C and dietary fiber potatoes contribute significantly to nutrients with defined roles in cardiovascular health (McGill et al., 2013). Reported health benefits derived phytochemical rich foods with similar phenolic profiles to those found in potatoes (anthocyanins and chlorogenic acids) include reduction of cardiovascular diseases, cancer and amelioration of diabetes (Akash et al., 2014; Ghosh and Konishi, 2007; He and Giusti, 2010; Manach et al., 2005a; Van Dam and Hu, 2005; Zafra-Stone et al., 2007). While the mechanism behind these effects and the extent to which these effects can be extended to potato products remain unclear, these observations combined with the contribution of potatoes to phenolic intake in the diet highlight the potential potato products may play in modifying risk factors. In these efforts it is important to consider the form of potato consumed as well as the potential for improvements in processed potato products in which the nutritional value of the potato can be leveraged. More recent research also supports the potential of potato products to contribute to weight management through promotion of satiety, despite the relatively high glycemic index of many potato forms (consumed alone) (Ek et al., 2012). Subjects in a study by Erdmann et al. (2007) consumed less energy when consuming potatoes compared to rice or pasta. Holt, et al. (1995) found that satiety ratings for potato were higher than other 37 foods measured, including fruits, bakery products, snack foods, carb-rich foods, protein-rich foods, and breakfast cereals. In general, higher protein, fiber, and water content in foods correlated with greater satiety ratings, whereas higher fat content correlates with lower satiety ratings (Holt et al., 1995). Diets that are high in satiating power and low in energy density may have positive implications for weight management (Drewnowski, 1998). However, while research suggests that low glycemic index foods can promote satiety in the short term, there is not strong enough evidence to conclude that consuming low glycemic

foods can regulate satiety and body weight in the long term (Bornet et al., 2007; Niwano et al., 2009; Raben, 2002).

1.6.3 Potatoes and Modulation of Oxidative Stress

Oxidative stress is defined as an imbalance in the organism’s production of reactive oxygen species (ROS) and the action of dietary or endogenous antioxidant systems (Betteridge, 2000). While antioxidant micronutrients (vitamin C), minerals (selenium) and bioactive (phenolics, tocopherols and carotenoids) present in potato are commonly considered to contribute to overall antioxidant activity of potatoes (Brown (2005) Lachman & Hamouz (2005), it is the phenolic fraction that has been found to be directly proportional to in vitro antioxidant activity (Leo et al., 2008). As with other fruit and vegetable extracts, higher phenolic and flavonoid content of colored-flesh potatoes has been correlated to a higher antioxidant activity. Specifically, colored-fleshed potatoes have been found to have 250-300% higher ORAC values than white potatoes (Brown et al., 2003; Navarre et al., 2011). Reddivari, et al. (2007) found that magnitude of antioxidant capacity (trolox eq.) of 25 specialty potato varieties grouped by skin/flesh color followed the order of Purple/Purple, Red/Red, Red Yellow/Yellow, Purple/Yellow, and Yellow/Yellow. While many in vitro antioxidant assays may not directly represent in vivo modulation of oxidative stress (Amorati and Valgimigli, 2015), these measures are still commonly used to assess the potential of potatoes to provide protection in vivo (Andre et al., 2009, 2007a; del Mar Verde Méndez et al., 2004). Ultimately, modulation of in vivo markers remains the most critical evidence to consider. Consumption of potatoes both with and without skins was found to positively influence lipid metabolism and antioxidant status in rats (Robert et al., 2008, 2006). Kaspar et al. (2011) demonstrated that consumption of colored potatoes reduced multiple markers of inflammation and oxidative stress in humans. However, in commonly consumed products from typical white potato varieties, such as baked and fried chips and fries, ascorbic acid may still remain a critical contributor to the ability of potato products to modulate markers of oxidative stress in vivo. Using a SMP30/GNL KO mice Kondo, et al. (2014) demonstrated that feeding fried potato chips elevated ascorbic acid levels and in turn lowered levels of reactive oxygen species (ROS) in tissues compared with AA-depleted mice. While promising, more evidence is needed to understand the specific role of potatoes and/or potato bioactive in modulation of oxidative

stress. To date, evidence on availability of potato phenolic antioxidants and carotenoids remains limited. Without more detailed pharmacokinetic assessments of potatoes bioactives in conjunction with long term trials conducted in relevant animal models and humans it will be difficult to leverage on preliminary findings and in vitro assessments of antioxidant content and activity for selection and application of strategic potatoes cultivars or for connection to specific health benefits including cardiovascular and GI health.

1.6.4 Potatoes and Modulation of Inflammatory Stress

Inflammation is a complex physiological response to an adverse stimuli presented by cellular/tissue damage or infection (Ryan and Majno, 1977). Oxidative stress is one mechanism that can trigger an inflammatory response, thereby linking the two underlying mechanism in disease pathologies (Federico et al., 2007). Most often studies investigating the impact of food on inflammatory stress assess specific molecular markers typical of the pathways for acute and chronic inflammation. This includes many (1) platelet activating factor (PAF) and derivatives of arachidonic acid, (2) inflammatory regulating cytokines and nitric oxide (Feghali and Wright, 1997). Data on the anti-inflammatory activity of potatoes has generally been limited to in vitro and animal studies and a focus on GI inflammation in particular. A chloroform extract of the peel from a colored-flesh potato (Jayoung) demonstrated the ability to attenuate oxidative and inflammatory processes both in LPS stimulated RAW 264.7 macrophages and in a dextran sulfate sodium mouse model of colitis (Lee et al., 2014). Kaspar et al. (2011) found anti-inflammatory effects in healthy men consuming white and pigmented potatoes with greater effects from pigmented potatoes. As described previously, potato peels are a rich source of both phenolics and glycoalkaloids. While phenolic from potatoes and other foods have demonstrated similar anti-inflammatory effects (Bogani et al., 2007; Vitaglione et al., 2015) potato glycoalkaloids have also shown evidence of both pro- (Iablokov et al., 2010) and anti-inflammatory activities (Kenny et al., 2013) dependent on application of sub-cytotoxic dose paradigms in rodent and cell models respectivly. While interesting, few studies have focused on the impact of potato products as part of an overall meal/diet. Further, the contribution of resistant starch or fiber from select potato products may have direct impact on inflammatory stress in the GI. Indigestible carbohydrates including resistant starch and fiber have demonstrated the ability to

modulate inflammatory markers in both animal models (Bassaganya-Riera et al., 2011; Fan et al., 2012; Vaziri et al., 2014) and human clinical trials (Jiao et al., 2015). Sweet potato resistant starch was also shown to ameliorate pro-inflammatory status in insulin resistant rats (Chen et al., 2013). Additionally, the potential for synergistic interactions between phenolics and prebiotic/anti-inflammatory effects of fiber resistant starch from potatoes exist and remains to be investigated. Therefore, in a manner similar to evaluation of impact to oxidative stress, experimental evidence in humans and relevant animal models is still lacking. Furthermore, mechanistic studies investigating synergistic effects of potato micro, macro and phyto-nutrients are clearly required to better understand the extent to which the potato as a food contributes to positive modulation of inflammatory stress and related disorders.

1.6.5 Glycemic Effect of Potatoes

An area that is perhaps more directly associated to nutrition and health outcomes is that of starch digestion and glycemic response. Considering the carbohydrate density of potatoes it is not surprising that glycemic response and effect of potato consumption remains central to many of the nutritional concerns and benefits related to products. The glycemic effect of potatoes has been the subject of numerous investigations and more recently reviewed in detail by Ek et al. (2012). Potato-based food products are generally classified as medium to high glycemic foods (Ek et al., 2012) by virtue of the starch content and general association of the highly digestible nature of potato starch. The term “glycemic index” (GI) was first introduced to classify carbohydrate-containing foods by their ability to raise blood glucose (Jenkins et al., 1981). High GI foods have values of 70 or above, medium GI have values between 56 and 69, and low GI foods have values lower than 55 (Bornet et al., 2007). High GI foods are generally regarded to be absorbed quickly and result in higher postprandial blood glucose spikes, which over time may increase risk of diet-related chronic diseases such as obesity, type-2 diabetes, cardiovascular disease , and some cancers (Liu and Willett, 2002; Ludwig DS, 2002). As a starch food, potatoes are often perceived as having a high GI and by extension potentially negative long-term health effects. However, the glycemic index of potato products can vary widely depending on the potato variety, maturity, and level of processing/preparation, including addition of other ingredients that modify glycemic

response. Using glucose as a reference food, values range from 41 (white, cooked) to 95 (instant), however, most fall between 50 and 90 (Atkinson et al., 2008). Glycemic load is another value developed to describe the carbohydrate digestibility of a food in the context of the amount typically consumed. The GL is the GI of a food normalized by the carbohydrate content of a typical serving size, allowing for comparison between foods. GL of potato products often falls between 11 and 25, which is lower than values typical for starchy foods including pasta (~15-40) and white rice (~15-35), but higher than wheat breads and several kinds of fruits, vegetables, and legumes (Foster-Powell et al., 2002). Potato variety and maturity can significantly impact glycemic response. In a study by Fernandes et al. (2005), baked Russet Burbank had a higher glycemic index than baked Prince Edward Island (PEI) or roasted California white potato. Henry et al. (2005) measured glycemic index of eight British potato varieties classifying four varieties (Estima, Charlotte, Marfona, Nicola) as “medium” glycemic response foods, while the other four (Maris Peer, Maris Piper, Desiree, and King Edward) were classified as “high” glycemic response foods. Generally, potatoes with more floury texture (low moisture and sugar, high starch) had higher GI than those with waxy texture (high moisture, low starch). Soh and Brand-Miller (1999) also found that the Desiree variety had higher glycemic index than Pontiac and Sebago varieties (peeled and boiled). In regards to maturity, these authors found that “new” (or young, immature) potatoes had lower glycemic index compared to mature Desiree, which is attributed to lower starch digestibility in new potatoes. Glycemic response to potatoes is also affected by preparation method, including extent of processing and ingredient addition. It has been shown that the formation of resistant starch in cooked and refrigerated potato products attenuates blood glucose response (Kanan et al., 1998). In data from Fernandes et al. (2005) with glucose as a reference food, cold boiled red potatoes had the lowest GI (56.2), and hot boiled red potatoes had the highest (89.4), which illustrates the significant impact of retrograded starch. From highest to lowest, values for instant mashed, baked Russet, baked PEI, roasted California white, and French fried potatoes fell between those two. The large reduction in GI between the hot and cold boiled red potatoes was greater than what could be explained by reduction in amount of starch digested alone, thus the authors pose that the majority of the reduction in GI was likely also due to a reduction in rate of starch absorption. In a study by Brand et al. (1985) in vitro digestibility of potato products was greatest for potato chips,

followed by instant potatoes and boiled potatoes. However, the GI of potato crisps was found to be the same as boiled potato and both were found to be significantly lower than instant potato. This may be due, in part, to the contribution of fat in the chips, which can serve to slow gastric emptying and thus starch release in the small intestine (Gentilcore et al., 2006). However, potato chips in this study exhibited lower glycemic index compared to corn chips and rice puffs, which could indicate some contribution from other nutrients specific to potato. While the data on glycemic effect of potatoes is varied, it is also important to note that in general, the glycemic effects of potato products have not been considered in the context of the diet. That is, as potatoes are generally consumed as a side dish, and thus the response of potatoes alone may have less relevance that the response within the context of a more complex meal. Other meal components, such as fat, protein, and acetic acid have been shown to modulate glycemic response (Collier and O’Dea, 1983; Gulliford et al., 1989; Liljeberg and Bjorck, 1998). Along with formulation factors and meal complexity, potato phytochemical composition may directly play a role in modulation of potato glycemic response. In addition to antioxidant and anti-inflammatory activities of phenolic compounds, more recent evidence points to the abilities of these dietary polyphenols to influence carbohydrate digestion, absorption and metabolism. Interestingly, Thompson et al. (1984) reported that phenolic content of foods including potatoes was inversely proportional to glycemic index. This observation was initially attributed to potential for interaction between complex phenolics and starch making starch less digestible (Barros et al., 2012; Deshpande and Salunkhe, 1982). However, more recently smaller molecular weight phenolics from multiple dietary sources including tea, cocoa, fruits and cereals have demonstrated the ability to modulate carbohydrate digestion, intestinal glucose transport and metabolism leading to reduced glycemic response (Hanhineva et al., 2010). A recent report from Ramdath et al. (2014) found a similar inverse correlation between polyphenol content of potatoes and glycemic index (GI) with colored anthocyanin and phenolic-rich potatoes having a more pronounced decrease in GI. While promising, these studies are preliminary and, to date, rely on differences between potato varieties that are not as commonly leveraged in fresh market or commercial products. Further, it remains unclear if the observed effects are related to alteration of starch structure (to form more resistant starch), starch digestion rate (through inhibition of digestive enzymes) or through

modulation of glucose transport. Further efforts to characterize impacts of processing and formulation on interactions between phenolics and potato starch are needed to better understand the potential of leveraging the native phenolics present in potatoes.

1.6.6 Potato Influences on the Microbiota

The recognition on the role of intestinal microbiota in general health and modulation of obesity and chronic disease has grown in recent years (DuPont and DuPont, 2011; Greiner and Bäckhed, 2011; Kootte et al., 2012). It is logical to consider potatoes, as a key source of starch, fiber and phenolics, as a potential modulator of gut microbiota communities and by extension selected benefits. Surprisingly, little is known regarding the impact of potato products on gut microbial diversity or metabolic activity. Raw potato starch has been shown to alter both purine base secretion and short chain fatty acid production in a growing pig model (Martinez-Puig et al., 2003). Raw potato starch fed at 9% of the diet was also shown to increase lactic acid bacteria in the caecum and proximal colon of rodents (Le Blay et al., 2003). While interesting these results have little practical application to processed and cooked potato products. Further, they do not consider the role of potato phenolics, such as chlorogenic acid, which have demonstrated the ability to alter bacterial communities in vitro and in vivo (Gonthier et al., 2006; Jaquet et al., 2009; Mills et al., 2015). Considering the potential for interactions between starch and phenolics and the ability to alter starch substrate utilization by bacteria (Wang et al., 2013), more research is needed to clarify the impact of potatoes on gut microbial communities.

Opportunities to Improve Nutritional Value of Processed Potato Products

Processing and preparation can both positively and negatively impact potato nutritional quality. Previous sections of this review have discussed opportunities to improve the nutritional quality of processed potato products, including variety and process selection to improve phytochemical and micronutrient content and retention. Additionally, emerging insights into the potential for interactions between potato macronutrients and phytochemicals in relation to bioavailability and glycemic response may impact overall nutritional quality. This section will give more depth on other processing strategies that

have the capacity to improve the nutritional profile of processed potato products. These have been the subject of several reviews (Burton, 1989; Decker and Ferruzzi, 2013; Foot et al., 2007; Keijbets, 2008; Nayak et al., 2014) with the focus primarily on salt reduction, improved lipid profiles, acrylamide reduction in fried products, and improvement of slowly digestible and resistant starch content.

1.7.1 Lipid Reduction

There are several factors that influence the absorption of fat into potato products which are discussed in depth by Burton (1989, chap. 11). Briefly, fat absorption is increased by larger surface area/volume ratio, lower frying temperature for chips, potato immaturity, and low dry matter (high moisture) content. Potato variety may also impact fat uptake (O’Connor et al., 2001). Prefrying treatments can be applied to potato products to limit lipid absorption. Pedreschi et al. (2008) found that potato chips which were pre- blanched absorbed more oil than control chips. However, others suggest that blanching gelatinizes starch on the surface of French fries and creates a moisture barrier (Miranda and Aguilera, 2006). Surface drying or pardrying (e.g. microwave, hot air) is currently used in the French fry industry to reduce oil absorption. Other treatments which have been shown to reduce oil absorption in fried products include cryogenic freezing, soaking in a sodium chloride solution, blanching with infrared radiation, and coating with film forming materials or hydrocolloid solutions (Mehta and Swinburn, 2001; Miranda and Aguilera, 2006). Lipid content and fatty acid profile of potato products will depend greatly on the fat/oil used in the processing or final preparation of the product. Therefore strategies to improve lipid profiles of fried potatoes have focused on (1) improvement of fat and oil nutritional quality and (2) minimization of fat absorption during the frying process (Bouchon, 2009; Fillion and Henry, 1998; Matthäus, 2006; Ziaiifar et al., 2008). As such, significant attention has been placed in improving the nutrition quality of frying oils by eliminating trans fat content (Berger and Idris, 2005; Daniel et al., 2005; Katan, 2006) and minimize saturated fat content to be more in line with recommendations of the 2010 Dietary Guidelines for Americans (Dietary Guidelines Advisory Committe, 2010). Technically this has been achieved through application of high mono-unsaturated fatty acid rich oils and blending technologies that have generated products of higher nutritional

quality with minimal impact to sensory properties of the final fried potato (taste, aroma and texture) (Farhoosh et al., 2008; Man et al., 1999; Matthäus, 2006). A second approach to improve the nutritional profiles of fried potatoes has been to leverage coatings technology and novel frying methods to minimize the absorption of fat into the final fried product. Considering that in a traditionally immersion fried product fat absorption occurs both following the loss of moisture from the potato during frying and continues after cooking (Bouchon et al., 2003), technologies that can minimize water loss and minimize fat absorption have been the focus for product improvements. Hydrocolloid based coating systems composed of gums, cellulose and proteins applied to raw potato surface have been shown to minimize fat uptake during frying by forming a protective barrier that minimizes both water loss and fat absorption during cooking (Garcı́a et al., 2002; reviewed by Mellema, 2003). Technologies that can improve on traditional immersion frying include vacuum frying and centrifugal frying which reduce frying temperatures and drain more oil after cooking respectively. While these technologies have been shown to decrease fat content of fried potatoes up to 75%, capital investment and suitability for all product types has limited their broad application. Similarly, new frying technologies such controlled dynamic radiant frying (CDRF) have demonstrated significant promise as an alternative to immersion frying reducing oil content by up to 50% in potato products (Lloyd, 2004). This technology relies on infrared radiation to simulate the heat transfer of the frying process and requires minimal oil to replicate the color, texture and flavor of typical fried products (Lloyd et al., 2004). While promising, the adoption of such technologies is often limited by the nature of the application. The potential of these technologies if leveraged across broad product types remains to be realized.

1.7.2 Resistant Starch Formation

As described previously, potato starch is a natural resistant starch in the RS2 form. When heated in water, hydrogen bonds within and between amylose and amylopectin molecules are broken, allowing the starch granule to swell, lose crystallinity, structural organization and gelatinize forming rapidly digestible starch (RDS). Upon cooling, starch molecules from the disrupted granules form a gel, and eventually retrograde into a semi- crystalline form producing both slowly digestible starch (SDS) and resistant starch type

RS3, which is resistant to digestive enzymes and may therefore slow glycemic response and contribute to dietary fiber (Raigond et al., 2014). Considering that retrogradation of gelatinized potato starch after cooking results in formation of SDS and RS (type 3) it is not surprising that interest in strategies to control starch digestion through formation of either slowly digestible (SDS) and resistant starch (RS) has grown. Implications for control of glucose release/response from potato products through functionalization of starch may serve to counteract the moderate to high glycemic characteristic of potatoes or alter substrate availability for microbial populations throughout the gut. The extent of formation of SDS and RS3 in potato products is dependent on the type and extent of processing (Brand et al., 1985; Thed and Phillips, 1995) as well as the manner in which they are consumed (Englyst and Cummings, 1987). Specifically, the extent of initial gelatinization through thermal processing or cooking is a critical first step as raw potato starch is as rich source of RS (type 2). Strategies to preserve a portion of the starch granule and RS2 structure could increase the relative levels of RS in finished potatoes. Some research suggests that cooking methods which provide sufficient water and heat for complete starch gelatinization may increase digestibility compared to dry heating methods, such as baking and frying (García-Alonso and Goñi, 2000; Lunetta et al., 1995). Others have found no effect of cooking method on glycemic index (Soh and Brand-Miller, 1999). Following gelatinization through boiling, baking frying or other heating mechanism; cooling of potatoes has been demonstrated to generate appreciable levels of SDS and RS3 and decrease glycemic index in vivo (Fernandes et al., 2005; Monro et al., 2009). Decrease in glycemic index is still observed upon reheating compared to products consumed immediately after processing (Tahvonen et al., 2006). Resistant starch content has been increased by temperature cycling, or more than one heating and cooling sessions (Englyst and Cummings, 1987; Leeman et al., 2005). Freeze drying chips before frying has also increased resistant starch to 32% compared to 1% in non-freeze dried chips (Goñi et al., 1997). These authors also observed formation of 7% resistant starch in whole French fries. This has applications for select product categories including prepared dishes or snacks where such approaches can be integrated into the processing unit operations resulting in novel products with improved glycemic response and by extension nutritional profile. Insoluble amylose-lipid complexes have been observed when amylose was heated with fatty

acids (Mercier et al., 2013). More research is needed on the effect of these complexes on glycemic index in fried potato products. Additionally, the extent to which these structures may impact microbial communities through the extent of the gastrointestinal tract needs to be better elucidated.

1.7.3 Management of Acrylamide Formation

Acrylamide, a byproduct of the Maillard reaction, occurs in a range of baked, fried, and roasted foods. It is produced from the reaction of reducing sugars and the amino acid asparagine, which is abundant in potatoes. Agronomic, genetic, and processing approaches to mitigation of acrylamide in processed potato products has been the subject of several reviews (Amrein et al., 2003; De Wilde et al., 2005; Foot et al., 2007; Muttucumaru et al., 2008; Zhang and Zhang, 2007). Briefly, methods to reduce acrylamide include reduction in reducing sugars and asparagine, reducing cooking time and/or temperature or exposure to high heat, addition of antioxidants, lowering pH, blanching or soaking to remove surface acrylamide precursors, and cutting with larger surface area to volume ratio. Additionally, Zhu, et al. (2010) found a fairly strong negative correlation (r=-.6918) between phenolic acid content of potato varieties and acrylamide formation during processing, suggesting that selection of high phenolic varieties may mitigate acrylamide formation.

Research Needs and Future Directions

Potatoes products remain an important dietary source of macronutrients, micronutrients and biologically active phytochemicals that have associated nutritional and health implications. While potato consumption has been both positively and negatively associated with select health endpoints, inconsistencies in definitions of potato products, their role in a broader diet pattern and differences in study designs, have made interpretation of these associations difficult. However, these outcomes have resulted in increased interest in nutritional value of potatoes and potato products. Mostly recognized as a starch rich vegetable, potatoes are less recognized for their contribution to overall dietary fiber or micronutrients including Ca, K, Mg, Fe, and Mn as well as vitamin C. In regards to bioactive phytochemicals, potatoes remain a significant contributor to overall

intake of phenolics, predominantly in the form of phenolic acids and specifically chlorogenic acids for white potatoes. While nutritional profiles of potato products have been characterized, information on the bioavailability of potato nutrients and phytochemical remains limited mainly to preclinical models and select clinical studies. In addition, many of the positive nutritional characteristics of potatoes are lost in consumer perception due, in part, to the suggestion that nutritional profile of potatoes can be altered by preparation and processing method which introduce limiters such as fat and sodium. Significant work has been done to capture the impact of in home preparation on potato nutritional profiles, suggesting that finished products do in fact carry substantial amounts of nutrients and phytochemicals. However, much less is known regarding the impact of commercial processing on these endpoints including bioavailability. This information remains critical to establish considering the increased prevalence and interest in processed products by consumers and the potential for these products to be optimized. As a starch rich food, the nutritional perception of potatoes still remains highly associated with the glycemic response from commonly consumed prepared or processed products. This has been the subject of intensive investigation yielding the general consensus that potato glycemic response will vary widely from low to high based on variety, starch structure, preparation and processing as it relates to generation of slowly digestible or resistant starch. However, more recently, phenolic profile of potatoes has shown promise as a modifier of starch digestion, intestinal glucose transport and ultimately may play a role in modifying glycemic response. While promising, insights into the response from commonly consumed potato forms, application of novel phenolic rich potato varieties (such as colored potatoes), and impact in the context of broader diet pattern are needed to determine the potential benefits provided by unique nutrient and phytochemical profiles on their own or in synergy. This includes a need to better understand how these interactions may impact functionality both in products and in the gut with specific consideration of the potential for impact to microbial communities and activities in the gut as these relate to specific underlying factors that modulate disease risk (gut function, substrate utilization, oxidative and inflammatory stress). Despite these gaps in knowledge, clear opportunities exist to capitalize on the known nutritional profile of potatoes. Considering the prevalence of processed potato products, leveraging new varieties or processing technologies to limit perceived negative nutritional

attributes (fat and sodium) while optimizing positive attributes (phytochemical content, micronutrient retention, resistant starch) holds promise for building better potato products. Additionally, the development of new strategies for leveraging nutrient dense waste streams, including peel waste, may offer novel approaches for enhancing nutrient density of commercial products. Finally, as our understanding of the nutritional attributes and quality of potato products grows, it is important to recognize that processing will be a key player in translation of nutrition enhancements to consumers.

CHAPTER 2. RESEARCH RATIONALE AND OBJECTIVES

As highlighted in the previous chapter, nutrient and micronutrient content of potatoes and potato products (including both potatoes and sweet potatoes) in addition to their wide consumption give them an important role in human nutrition. In addition, potatoes contribute significantly to the overall dietary intake of health-promoting phytochemicals (Chun et al., 2005; Liu, 2013), providing another dimension to their potential relationship to human health. While promising, the shift in consumer preference for more convenient “processed” products compared to freshly prepared has coincided with the negative nutritional association of potato products and health. However, limited information is actually available on the extent to which commercial processing of potatoes impacts nutritional quality. In the case of our research, it is unclear the extent to which the type and amount of processing may affect the phytochemical content of commonly consumed products. While the phytochemical content of select pigmented and commercial non- pigmented potatoes has been well-researched, very few investigations have directly compared phytochemical profiles between commercially relevant pigmented and non- pigmented varieties. In addition, existing research on process stability of potato phytochemicals has yielded disparate results due to a number of factors that may or may not be controlled. Existing research on process stability of potato phytochemicals also usually includes laboratory- or kitchen-scale cooking or preparation methods, rather than commercial processing methods (which are more relevant to the American diet). Finally, there is a lack of comparison of the effects of commercial and fresh preparation methods on phytochemical content and composition. Based on these gaps, the overall objective of this research was to investigate phytochemical content in commercially relevant cultivars and determine the effects of commercial and fresh processing on phytochemical content. To achieve this objective, three experiments with separate aims were conducted.

Experiment (Aim) 1: Determine phytochemical content in fresh commercially relevant potato varieties. Nine commercial varieties (6 yellow/white, 2 purple, 1 red, 1 sweet potato) were obtained from McCain foods and analyzed for phenolic acids, anthocyanins, and carotenoids. It was hypothesized that potato varieties would differ significantly in levels of chlorogenic acids and anthocyanin derivatives with pigmented varieties having higher overall phenolics. Also, sweet potato varieties would contain high levels of carotenoids.

Experiment (Aim) 2: Determine the extent to which key phenolics including chlorogenic acid and anthocyanins are recovered through commercial processing. Four varieties of commercially processed, dried, and ground potato samples (1 white, 2 purple, 1 red) were obtained from McCain foods. Whole potatoes and potato flesh were compared through five processing treatments (blanched and frozen; blanched, fried, and frozen; blanched, fried, frozen, and fried; blanched, fried, frozen, and baked) for each variety. It was hypothesized that peeling and progressive processing would reduce chlorogenic acid and anthocyanin content in each variety, though effects of treatments would vary in impact based on phenolic species (anthocyanins would be more stable than CGA).

Experiment (Aim) 3: Compare the impact of fresh preparation to commercial processing on chlorogenic acid and beta-carotene recovery. Five frozen and reconstituted commercial samples (Classic Fries, Fresh-Style Fries, Hash Browns, Sweet Potato Fries, and Sweet Potato Wedges) were compared to similarly- produced fresh products. It was hypothesized that phytochemical content in freshly prepared products would be greater than that of commercially produced and reconstituted products.

CHAPTER 3. PHYTOCHEMICAL CONTENT IN COMMERCIALLY RELEVANT POTATO VARIETIES AND PROCESS STABILITY IN COMMERCIAL AND FRESH POTATO PRODUCTS

Abstract

Potatoes (Solanum tuberosum) are a significant source of health promoting phytochemicals. However, reported content and process stability of phytochemicals in potato products is inconsistent. The objectives of this study were to compare phytochemical content in white/yellow and pigmented commercially relevant varieties, determine changes in phytochemical content of select potato varieties through commercial processing, and assess differences in phytochemical content between freshly “home” prepared and reconstituted, commercially processed white and sweet potato products. Total chlorogenic acids (CQAs) ranged from 43-953 mg/100 g dw and were found in greater concentrations in the whole of all varieties compared to flesh, as well as in pigmented potatoes compared to white/yellow-fleshed potatoes. 5-0-CQA was the primary chlorogenic acid isomer detected in all varieties of potato, followed by 4-0- and 3-0-CQA. Acylated anthocyanins in red potatoes were primarily cyanidin pelargonidin derivatives, while those in purple varieties were primarily petunidin with smaller amounts malvidin and delphinidin derivatives. Commercial products included raw flesh without skin (FNS), blanched+frozen (BF), +microwaved (BFM), and blanched+par-fried+frozen (BFF), +baked (BFFO) or +fried (BFFF). Retention ranged from 49-85% for pigmented varieties and 32- 55% for white. For purple and red varieties, CQA levels were significantly lower (p<0.05) in BFF, BFFO, and BFFF compared to FNS, BF, or BFM products. For white, CQA levels were lower (P<0.05) in all processed products compared to FNS, but no differences were observed between processing levels. Comparing fresh to commercial products, levels of CQA did not differ for classic fries, fresh-style fries, or sweet potato fries, but were significantly (p<0.05) lower in industrial baked and fried sweet potato wedges and baked and pan-fried

hash browns. Retention of anthocyanins through all forms of processing was high (69- 129%). Sweet potato -carotene was higher in commercial baked wedges (30 mg/100g dw) compared to fresh prepared (26 mg/100g) (p<0.05), but no other differences between fresh and commercial products were found. These results suggest that commercial blanching, freezing, and microwaving have mild impact on phytochemical levels in raw potatoes compared to par-frying and subsequent baking or frying. Additionally, industrial products compare favorably to freshly prepared products in recovery of phytochemicals.

Introduction

Potatoes, encompassing both common tubers (Solanum tuberosum) and sweet potatoes (Ipomoea batatas), are important staple food in both the developing and developed world. High yields, agronomic versatility, resilience in world markets, and nutritive value give potatoes high potential to be an excellent “food security” crop (Camire et al., 2009; Food and Agriculture Organization of the United Nations, 2008a; Govindakrishnan and Haverkort, 2006). Potato tubers are the most widely consumed vegetable in the American diet, comprising about 30% of total vegetable consumption for men and women (Storey and Anderson, 2013). Potatoes are an important staple source energy as well as several vitamins and minerals, including vitamin C, vitamin B6, niacin, folate, potassium, iron, and magnesium (Cotton et al., 2004; Kärenlampi and White, 2009; US Department of Agriculture Agricultural Research Service, 2014). While botanically distinct from S. tuberosum tubers, sweet potatoes (I. batatas), a root member of the Convolvulaceae family, also have several vitamins and minerals, most notably high levels of vitamin A and carotenoids (in orange- fleshed varieties) (Bovell-Benjamin, 2007). While the combination of high consumption and nutritional quality make both forms of potatoes a key nutritional contributor to overall diet nutrition, it is important to note that potatoes also contribute a significant amount of health promoting phytochemicals to the American diet (Chun et al., 2005; Liu, 2013). Diets high in phytochemicals, including phenolics and carotenoids, have been associated with a reduce risk of chronic and degenerative diseases including cardiovascular disease and some cancers (Crozier et al., 2009; Manach et al., 2005a; McGill et al., 2013). While not contributing to traditional nutritional value, these phytochemicals are believed to modulate disease risk through

several mechanisms including combinations of antioxidant and anti-inflammatory activities (Kaspar et al., 2011; Liu, 2013; Robert et al., 2006). Some studies suggest that these phenolic compounds are also able to modulate glycemic index of potatoes (Ramdath et al., 2014; Thompson et al., 1984). Potatoes are broadly considered to be rich sources of phenolic acids and flavonoids. Chlorogenic acids (3-,4-, and 5-O-caffeoylquinic acids) are reported to be the most common phenolic derivative in potatoes with levels ranging from 30 to 1360 mg/100 g dw. Caffeic acid has also been commonly reported in various potato cultivars at lower levels (0.5-14 mg/100 g dw) (Andre et al., 2007b; Navarre et al., 2011; Zhu et al., 2010). Other phenolic acids such as ferulic and p-coumaric acids are reported inconsistently at low levels (del Mar Verde Méndez et al., 2004; Deusser et al., 2012). Flavonoids in potatoes may include quercetin, kaempferol, rutin, and catechin, with the addition of anthocyanins in colored (red and purple) varieties (Andre et al., 2007b; Deusser et al., 2012; Jansen and Flamme, 2006). In general, purple-fleshed varieties are rich in petunidin, malvidin, and peonidin glycosides and derivatives, while red-fleshed varieties are rich in cyanidin and pelargonidin glycosides and derivatives (Brown, 2005; Eichhorn and Winterhalter, 2005). Sweet potatoes, like potatoes, contain phenolic acids and flavonoids, especially in purple- or red-fleshed varieties (Oki et al., 2002; Teow et al., 2007). However, orange fleshed sweet potatoes, common in the American diet, are rich sources of carotenoids including beta-carotene (Huang et al., 1999; Takahata et al., 1993). Potatoes are unique compared to other vegetables and fruits in that they are exclusively consumed in processed forms, whether industrially processed or prepared in a restaurant or home. Approximately 60% of the fresh potato crop is typically used for industrial processing into products such as French fries and chips, whereas the remaining ~40% is sold on the fresh market for home and fresh food service applications (Bradshaw and Ramsay, 2009; USDA Economic Research Service, 2014). Considering the diversity of types and extent of processing that potatoes are subjected to, it is important to understand the potential impact on potato nutritional quality including the recovery of potato phytochemicals through the process. This is particular critical considering the growing consumer distrust for “commercially processed foods”, including potato products, has risen, due in part to the notion that processing leads to significant reductions in nutritional and functional qualities compared to freshly prepared products.

Existing reports suggest both high and low stability of phytochemicals to typical processes. Navarre and others (2010) reported increases in various phenolics and flavonoids through boiling, steaming, microwaving, and baking. Other groups have reported similar increases, especially for phenolic acids (Blessington et al., 2010; Deusser et al., 2012; Mattila and Hellström, 2007). However, several studies suggest poor retention, as low as 0% and commonly around 60%, for several varieties and preparation methods (Dao and Friedman, 1992; Im et al., 2008; Lachman et al., 2013; Juan A. Tudela et al., 2002; Xu et al., 2009). While insightful, these reports are highlighted by the high level of variability that can be attributed to many factors including compound analyzed and analytical recovery, variety type, growing location, food matrix, and processing conditions. Processing conditions are perhaps most critical considering that most studies have relied on in home or fresh processing (Blessington et al., 2010; Im et al., 2008; Navarre et al., 2010; Xu et al., 2009) to investigate recovery of phytochemicals rather than commercial scale processing used to make typical consumer products. Insight into the impact of commercial processing on potato phytochemicals is needed in order to define optimal conditions to deliver high quality and health promoting commercial products. The overall goal of this research was therefore to understand the effects of various forms of processing on potato phytochemicals and the influence of potato variety and extent of processing on recovery of bioactive phytochemicals. Additionally, phytochemical recovery was compared between commercially processed and freshly prepared products, in order to determine the extent of difference between commercially processed and in home preparations.

Materials and Methods

3.3.1 Chemicals and Standards

Citric acid, chlorogenic acid (5-O-caffeoylquinic, 4-O-caffeoylquinic), ethyl gallate, and cyanidin-3-glucoside standards were purchased from Sigma-Aldrich (St. Louis, MO). Beta-carotene and lutein standards were purchased from Sigma Aldrich, Fluka (St. Louis, MO). Formic acid, LC and MS grade water, LC methanol, and acetonitrile were obtained from Avantor, J.T. Baker (Center Valley, PA). Fresh and processed potato samples were donated by McCain Foods USA, Inc. (Lisle, IL).

Sampling and Processing Procedures

3.4.1 Experiment 1: Preparation of Fresh Potatoes for Determination of Phytochemical Content

Ten varieties of fresh 2013 field samples were obtained from McCain Foods. These included nine Solanum tuberosum varieties (Innovator (yellow), Bintje (yellow), Challenger (yellow), Yukon (yellow), AR2009-10 (AR2; purple), Adirondack Blue (ADB; purple), Adirondack Red (ADR; red), Russet Burbank (white), Norland (white flesh, red skin)) and one Ipomoea batatas variety (Covington; orange-fleshed). Fresh samples were held in storage at 10°C until sampling for analysis. Potatoes of varying sizes were randomly selected, three for peeling and three for whole. Potatoes were rinsed in cool water, peeled or left whole, sliced to 1/8 in., dipped in 0.5% citric acid solution, frozen at -80°C overnight, and lyophilized (SP Scientific, VirTis; Warminster, PA) over 51 hours. Dried potato slices were pooled, transferred to zip-lock bags, double bagged, and stored at -20°C until grinding using a KitchenAid coffee grinder (Benton Harbor, MI) and analysis.

3.4.2 Experiment 2: Sampling of Commercially Processed Samples for Determination of Phytochemical Content

Four varieties of processed, lyophilized, and ground samples (AR2, ADR, ADB, R. Burbank) were received from McCain Foods and stored at -20°C. Samples included potatoes collected and processed to freeze dried powder from each step in the commercial processing to French fries (Figure 1). This included fresh flesh with skin (FWS); fresh flesh without skin (FNS); flesh blanched and frozen (BF); flesh blanched, frozen, and microwaved (BFM); flesh blanched, fried, and frozen (BFF); flesh blanched, fried, frozen, and fried (BFFF); and flesh blanched, fried, frozen, and baked (BFFO).

Figure 3. Schematic of commercially processed potato samples obtained from McCain foods for phenolic and anthocyanin analysis. All treatments were conducted on four varieties of potatoes with different flesh colors: AR2 (purple), ADB (purple), ADR (red), R. Burbank (white).

3.4.3 Experiment 3: Sampling and Reconstitution of Commercially Processed Frozen Products for Comparison of Phytochemical Content.

Five types of commercial frozen prepared products were obtained from McCain Foods: classic cut fries (MCF), fresh-style fries (includes peel) (MFF), hash browns (MHB), sweet potato fries (MSF), and sweet potato wedges (MSW). MCF, MFF, and MHB were produced from R. Burbank potatoes, while MSF and MSW were from the Covington variety. Three bags of each product were sampled and equivalent portions of each bag were pooled to make one sample. All pooled samples were reconstituted by baking or frying according to the instructions provided on the package. Frying. (MCFF, MFFF, MSFF, and MSWF) Frozen potato slices or wedges were fried in an electric fryer (Keating of Chicago, Inc., McCook, IL) for 4 min. in oil (Clear Liquid Canola Frying Oil, Bunge Oils, St. Louis, MO) at 176°C.

Panfrying. (MHBP) Frozen hash browns were pan-fried in canola oil for 12 min. at 176°C. Baking. (MCFB) Frozen product was baked in a convection oven (Vulcan (ITW Food Equipment Group, LLC.), Baltimore, MD) for 15 min. at 230°C, stirring once. (MSFB, MSWB) Frozen products were baked for 10 min. at about 218°C. (MHBB) Frozen product was tossed in canola oil until coated and baked for 8 min. at 218°C.

3.4.4 Experiment 3: Preparation of Freshly Prepared Products for Comparison of Phytochemical Content.

Fresh versions of the above commercial products were prepared using fresh raw potatoes provided by McCain foods from the same lot used to make the commercial frozen products. These included fried and baked classic fries (PCF), sweet potato fries (PSF), sweet potato wedges (PSW), and hash browns (PHB) and fried fresh-style fries (PFF). At least 6 raw potatoes of various sizes were sampled and pooled for preparation of each product. PCF, PHB, and PFF products were prepared from R. Burbank potatoes, and PSF and PSW were prepared from Covington. Cooking procedures followed typical recipes for homemade potato products. Classic Fries (PCF). Potatoes were lightly washed, peeled, and sliced to 3/8” thickness. Slices were rinsed in cold water, soaked for 45 min. at 4°C, drained, patted dry, and either fried or baked. Fried. (PCFF) Slices were par-fried in canola oil for 5 min. at 150°C. After resting for 30 min., slices were fried again at 176°C for 3 min. Baked. (PCFB) Slices were tossed in canola oil to coat and baked at 230°C for 15 min., stirring once. Fresh-Style Fries (PFF). Potatoes were lightly washed and sliced (unpeeled) to 3/8” thickness. Slices were rinsed in cold water, soaked for 45 min. at 4°C, drained, patted dry, and par-fried (PFFF) in canola oil at 5 min. at 150°C. After resting for 30 min., slices were fried again at 176°C for 3 min.. Hash Browns (PHB). Whole potatoes were scored with a knife, boiled for 8 min., transferred to ice water, then the peel was removed. Peeled potatoes were grated in a food processor then squeezed dry and pan-fried or baked. Pan-fried. (PHBP) Grated potato was panfried in canola oil at 176°C for 6 min., flipping once. Baked. (PHBB) Grated potato was tossed in canola oil and baked at 218°C for 8 min.

Sweet Potato Fries (PSF). Sweet potatoes were lightly washed, peeled, and sliced to 3/8” thickness. Slices were rinsed in cold water and drained to remove excess water, shaken with corn starch in a zip-lock bag, then either fried or baked. Fried. (PSFF) Slices were fried in canola oil at 176°C until golden brown, or about 7 min. Baked. (PSFB) Slices were coated in canola oil and baked for 15 min. at 218°C, stirring once. Sweet Potato Wedges (PSW). Sweet potatoes were lightly washed, peeled, and cut to ~1 in. wedges. Wedges were boiled for 5 min., cooled and patted dry, then either fried or baked. Fried. (PSWF) Wedges were par-fried in canola oil at 150°C until just browning, or about 3 min. After resting for 30 min., wedges were fried at 176°C until puffed, or about 5 min. Baked. (PSWB) Wedges were coated in canola oil and baked for 15 min. at 218°C, stirring once. After processing by baking or frying, all commercial and fresh products were cooled to room temperature, transferred to zip-lock bags, double bagged, and frozen at -80°C. Frozen products were subsequently broken into pieces then lyophilized over 51 hours. Dried samples were stored at -20°C. Samples were ground before analysis using a coffee grinder and a mortar and pestle for high fat samples.

Figure 4. Preparation of samples for Experiment 3- comparison of CQAs and beta-carotene in commercially processed and freshly prepared products. Codes beginning with “M” correspond to commercial version and codes beginning with “P” correspond to the fresh version for each of the products (Classic Fry, Fresh Style Fry, Hash Browns, Sweet Potato Fry, Sweet Potato Wedge). Products on the left were prepared from R. Burbank potatoes; products on the right from Covington sweet potatoes.

3.4.5 Phenolic Acid and Anthocyanin Extraction and Analysis

Extractions were conducted using ~0.4 g of lyophilized materials. Sample were first extracted twice with 5 mL of hexane to remove lipids, then dried under a stream of nitrogen at 37°C to remove residual solvent. After re-weighing the powders, 5 mL of extraction solution (80% methanol, 20% water, 2% formic acid) was added to each sample tube. Tubes were shaken for 15 min., sonicated for 45 min., and shaken for another 5 min., then centrifuged and supernatant was collected and dried under nitrogen. The remaining pellet underwent a second heated extraction to facilitate release of remaining polyphenols. 1 mL of 2% formic acid in water was added to each tube, then the sample was heated for 15 min. in a water bath at 60°C. 5 mL of the extraction solution was added, and after vortexing the tubes were sonicated for 15 min. at 45°C. The samples were centrifuged and the combined supernatants were dried under nitrogen. Dried samples were reconstituted with 5 mL of 2% formic acid in water prior to analysis. Overall extraction recovery, determined using spikes of 1000 M ethyl gallate as an internal standard added to potato poweder prior to extraction, ranged between 80-115%. For phenolic analysis, 2 mL of sample was filtered through a 0.45 휇m PTFE filter and 10 uL were injected into a Waters 2695 HPLC (Milford, MA) with a Waters X-Bridge Shield RP18 column (2.5 µm, 2.1x100 mm) heated to 40°C. HPLC and mass spectrometer conditions were adapted from Song et al. (2013) Anthocyanins and phenolic acids were analyzed in two separate methods but both using gradients of 2% formic acid in MS grade water (mobile phase A) and 0.1% formic acid in acetonitrile (mobile phase B) at a flow rate of 0.25 mL/min. For anthocyanin separation, solvent composition was 95, 65, 30, and 95% mobile phase A at 0, 15, 18, and 19 min., respectively. For phenolic acid separation, solvent composition was 95:5 (A:B) followed by a linear gradient to 65:35 (A:B) over 15 min and to 50:50 (A:B) at 17 min followed by a reset to initial conditions at 18 min. Column effluent was split (50:50) to a Waters 2996 photodiode array detector and a Waters Micromass ZQ mass spectrometer. Positive mode electrospray ionization (ESI) was used to detect anthocyanins. Conditions included: source temperature set to 150°C ; desolvation temperature set to 250°C.; nitrogen flow rates for desolvation and cone gas were 250 and 25 L/hr respectively. Capillary, cone, and extractor voltages were set to 2500, 50, and 3 V respectively. Anthocyanins were detected by single ion responses set to m/z 272, 287, 301, 303, 317, and 331 for pelargonidin, cyanidin, peonidin, delphinidin, petunidin, and malvidin

aglycone fragments respectively. All anthocyanins were quantified using cyanidin-3- glucoside standard. Peaks for each respective anthocyanidin SIR were quantified and added together to obtain a total anthocyanin content. Phenolic acids were detected in negative mode ESI. Conditions included: source temperature set to 150°C and desolvation temperature set to 250°C; nitrogen flow rats for desolvation and cone gas were 400 and 60 L/hr respectively. Capillary, cone, and extractor voltages were set to 3000, 40, and 5 V respectively. Single ion responses (SIRs) were set to m/z 353 and 179 for chlorogenic and caffeic acids. Identification of chlorogenic acids were made using standards 5-O- caffeoylquinic (5-CQA) and 4-O-caffeoylquinic (4-CQA) acids and comparison with previous literature. 5-CQA standard was used for quantification of all chlorogenic isomers. Limits of detection and quantification for chlorogenic acids were 5 and 17 ug/g dw, respectively. Cyanidin-3-glucoside standard was used for quantification of all anthocyanidin peaks. Anthocyanin limits of detection and quantification were .06 and 0.2 ug/g, respectively.

3.4.6 Carotenoid Extraction and Analysis

For extraction and analysis of fat soluble carotenoid pigments, ~0.3 g of lyophilized potato powder was vortexed with 2 mL of deionized water for 10 s, then left on ice for 10 min. 5 mL of chilled acetone was added and the mixture shaken for 5 min. and cooled with ice for 5 min. After centrifugation, the supernatant was collected and set aside. Extraction was repeated and the combined supernatants were dried under nitrogen until acetone had evaporated. The remaining potato solids were then extracted with 3 mL of methyl-tert- butyl ether (MTBE) containing 0.1% butylated hydroxytolulene (BHT) following the same procedures as the acetone extraction. Supernatant from the MTBE extraction was added to the dried supernatant from the acetone extraction. The mixture was vortexed and centrifuged and the organic layer transferred to a new test tube. The MTBE extraction was repeated on the potato solids and the organic layer combined in the same test tube. Each sample was dried under nitrogen and then resolubilized in 200 uL of ethyl acetate with 0.1% BHT, filtered through a 0.45 휇m PTFE filter, allowed to rest for 10 min. before analysis. 10 uL of each sample was injected onto a Waters Acquity H-class UPLC equipped with a Waters Acquity UPLC BEH C18 column (1.7 휇m, 2.1x100 mm) heated to 40°C. A gradient of 93:5:2 water:acetonitrile:2M ammonium acetate (mobile phase A) and acetonitrile (mobile phase B) at a flow rate of 0.8 mL/min was used. For carotenoid separation, solvent

composition was 23, 20, 5, 0, and 23% mobile phase A at 0, 3, 4, 10, and 11 min., respectively. Compounds were detected using a Waters Acquity UPLC PDA detector with a QDa detector monitoring from 250-550 nm and peaks were integrated at 450 nm. Pure beta-carotene and lutein standards were used for quantification. Percent recovery (average 78%) was determined by spiking samples with internal standard before extraction and comparing the resulting value to pure internal standard. Limits of detection and quantification for beta-carotene were 0.03 and 1.0 ug/g dw, respectively, and 1.3 and 4.5 ug/g for lutein.

3.4.7 Statistical Analysis

Commercial samples from Experiment 1 included three true replicates (each replicate consisting of a pooled sample from several potatoes) for each treatment. Each of these replicates was extracted and analyzed once. Samples for Experiment 2 and 3 were pooled samples containing at least 3 individual potatoes and were analyzed in triplicate. Statistical analysis for significance on data from Experiments 1 and 2 was conducted using 2-way ANOVA with Tukey-Kramer for pairwise comparison (significance level p ≤ .05) with JMP version 11 (SAS Institute, Inc., Cary, NC). Statistical analysis for significance on data from Experiment 3 was conducted using least squares comparison of means and a Bonferroni correction with SAS version 9.4.

Results and Discussion

3.5.1 Experiment 1: Phytochemical Content in Fresh Commercial Varieties

3.5.1.1 Phenolics

Chlorogenic acid derivatives (CQAs) were the most abundant phenolic species found in all varieties of potatoes analyzed. This is consistent with previous reports on potato phenolic profiles (Brown, 2005; Ezekiel et al., 2013). Also in agreement with previous reports, 5-O-caffeoylquinic acid (chlorogenic acid; 5-CQA) was the primary chlorogenic acid form (p<.05) in all varieties, followed by 4-O-caffeoylquinic (crytochlorogenic acid; 4-CQA) and 3-O-caffeoylquinic acid (neochlorogenic acid; 3-CQA) (Navarre et al., 2011; Zhu et al., 2010). While all varieties contained significantly different amounts of 5-CQA in the flesh, many varieties contained similar amounts of 3 and 4-CQA, indicating that 5-CQA is the main contributor to differences in total CQAs. All varieties contained significantly (p<.05) greater amounts of 4-CQA than 3-CQA except for Yukon and Challenger. Order of varieties in terms of total CQA levels in flesh was ADR > AR2009-10 > ADB > Innovator, R. Burbank, Norland, Yukon, Bintje, Challenger. When looking at whole varieties, Norland would move higher up in the list (after ADB) because its phenolics are more concentrated in its red peel. Overall levels of CQAs in pigmented varieties are similar to levels (~375 mg/100 g dw) found in brewed Robusta coffee (Rothwell et al., 2013). 3-CQA and 4-CQA were not detected in whole or flesh of the Covington sweet potato. However, these acids are present in processed forms of this variety (Table 11). Dawidowicz and Typek (2014) demonstrated increases in 3-CQA, 4-CQA, and other 5-CQA degradation products in blueberries, though the time and temperatures were higher than those used in this study. Takenaka (2006) also reports the increase in 3-CQA and 4-CQA in sweet potatoes upon processing by heating suggesting the increase is generated through enzymatic action. The extent to which this may have occurred was not investigated in this study. Overall, colored-fleshed (red and purple) varieties contained much higher levels of total CQAs (358-953 mg/100 g dw in whole) than white or yellow-fleshed varieties (43-88 mg/100 g dw in whole) (Figure 3). In general, as previously reported, whole potato

contained greater concentrations of CQAs than the flesh alone suggesting a higher distribution of these phenolic into the skin (Deusser et al., 2012; Lewis et al., 1998). However, the peel to flesh ratio varied between cultivars. For example, in purple-fleshed ADB and AR2009-10, CQAs in flesh and whole were relatively equal, while whole R. Burbank contained 75% more than R. Burbank flesh. This suggests that especially for pigmented potatoes, products which contain only the flesh and no peel still offer significant levels of CQAs originating from flesh. Free caffeic acids were found are relatively low levels (3.7-23 mg/100 g dw) in the peel of all varieties except R. Burbank and Covington sweet potatoes and in the flesh of only the ADR variety (Table 7). Other hydroxycinammic and hydroxybenzoic acids (ferulic, p- coumaric, vanillic, and gallic acids) and non-anthocyanin flavonoids (rutin, kaempferol, kaempferol-3-rutinoside) were detected in several varieties but not quantified due to low and inconsistent levels (Appendix A). Other studies have quantified these phenolics in several varieties (Deusser et al., 2012; Navarre et al., 2011). Though some have detected significant levels of catechin in other varieties (del Mar Verde Méndez et al., 2004; Mäder et al., 2009), this study did not detect catechins in any varieties.

Table 7. CQA and caffeic acid in whole potatoes and potato flesh of nine commercial potato varieties and one commercial sweet potato variety.

mg polyphenol/100 g dw Neochlorogenic Cryptochlorogenic Chlorogenic Variety Total CQAs Free Caffeic Acid (3-CQA) (4-CQA) (5-CQA) W 12.8 ± 0.2a1 14.5 ± 0.2b 47.1 ± 2.5c1 74.4 ± 3.61 11.9 ± 0.5 Innovator F 10.3 ± 0.0a2,D 11.4 ± 0.0b,E 58.7 ± 2.1c2,E 80.3 ± 5.41,DE n.d. W 10.4 ± 0.1a 10.9 ± 0.2a 22.6 ± 1.2b1 43.8 ± 2.71 9.62 ± 1.3 Bintje F 10.2 ± 0.2a,D 10.1 ± 0.2a,G 14.1 ± 0.9b2,H 34.4 ± 1.32,F n.d.

W 10.8 ± 0.1a 11.4 ± 0.3a 21.1 ± 2.4b1 43.3 ± 9.91 21.7 ± 0.9 Challenger F 9.91 ± 0.2a,D 10.0 ± 0.2a,G 15.0 ± 0.5b2,H 35.0 ± 1.92,F n.d. W 10.7 ± 0.2a 11.6 ± 0.2a 38.5 ± 0.2b1 60.8 ± 2.61 6.34 ± 1.2 Yukon F 10.1 ± 0.1a,D 10.5 ± 0.1a,FG 17.5 ± 0.4b2,G 38.1 ± 1.61,EF n.d. W 11.3 ± 0.1a 13.3 ± 0.1b 62.2 ± 1.0c1 86.7 ± 3.61 n.d. R. Burbank a,D b,EF c2,F 1,DE F 9.86 ± 0.1 10.8 ± 0.6 40.5 ± 5.9 61.1 ± 7.9 n.d. W 14.5 ± 0.2a 48.2 ± 2.8b 553 ± 8.9c1 616 ± 121 15.7 ± 3.4 AR2009-10 F 12.7 ± 0.5a,C 43.1 ± 1.1b,B 566 ± 22c1,A 622 ± 331,B n.d. W 24.9 ± 1.6a 89.5 ± 1.2b 839 ± 5.7c1 953 ± 4.61 23.4 ± 2.5 ADR F 18.5 ± 0.4a,B 64.9 ± 1.5b,A 731 ± 18c1,A 814 ± 252,A 14.6 ± 1.5 W 16.9 ± 0.4a 27.2 ± 3.8b 314 ± 45c1 358 ± 8.01 3.69 ± 2.3 ADB a,C b,D 1,C F 12.1 ± 0.1 25.8 ± 0.3 291 ± 2.0c1,B 329 ± 6.1 n.d. W 17.5 ± 0.4a 22.4 ± 0.8b 48.4 ± 1.8c1 88.3 ± 9.21 8.46 ± 1.7 Norland F 10.5 ± 0.3a,A 11.8 ± 0.2b,C 17.8 ± 0.9c2,D 39.4 ± 1.32,EF n.d. W n.d. n.d. 149 ± 77 149 ± 77 n.d. Covington F n.d. n.d. 100 ± 36 100 ± 36 n.d.

Each value represents the average of three analytical replicates with standard deviation. Lowercase letters represent significance (p<.05) within variety and potato part (across a row). Number represents significance (p<.05) between potato parts. Uppercase letters represent significance (p<.05) between varieties and potato parts (down a column; flesh used for comparison). Total CQAs are the sum of the three CQA after quantification. W= whole; F= flesh. Innovator= cream flesh, tan peel; Bintje= light yellow flesh, tan peel; Challenger= light yellow flesh, tan peel; Yukon= yellow flesh, tan peel; R. Burbank= white flesh, brown peel; AR2009-10 and ADB= purple flesh, purple peel; ADR= red flesh, red peel; Norland= white flesh, red peel; Covington= orange flesh, brown peel.

Figure 5. Average total CQA’s in flesh and whole of nine commercial Solanum tuberosum varieties. Error bars represent standard deviation.

3.5.1.2 Anthocyanins

The LC-MS method utilized in this study was adapted from that reported by Song et al. (2013). This method uses higher cone voltages to fragment native anthocyanins to their corresponding anthocyanidin backbone and thus facilitate quantification by corresponding response of aglycone. As such results are expressed as total anthocyanin content by class of anthocyanidin. Three colored raw varieties were analyzed- AR2009-10 (purple), ADB (purple), and ADR (red). Petunidin derivatives were the primary anthocyanin forms in AR2009-10 with smaller amounts of delphinidin, malvidin, and peonidin, while cyanidin and pelargonidin derivatives dominated the red-fleshed ADR (Table 8). ADB contained all anthocyanidin derivatives, though petunidin again dominated in this purple-fleshed variety. This illustrates that even varieties of very similar color can vary in anthocyanin profile. Flesh and whole of purple varieties contained similar levels of total anthocyanins, while red ADR had significantly more anthocyanins in whole than flesh.

While individual glycosides and other anthocyanin derivatives were specifically identified, tentative identification of simple anthocyanidin-glucosides – arabinosides and galactosides were identified by comparison to previous separations in our group (Song et al 2012; 2013) and corresponding elution order compared to cyanidin-3-glucoside standard. Further, it has been established that colored-fleshed potatoes and sweet potatoes contain a variety of acylated anthocyanins, and lower levels of simple glycosides (Mulinacci et al., 2008; Song et al., 2013). The predominance of acylated anthocyanins in the pigmented potatoes analyzed in this study was also confirmed by the later retention time (Figure 4), again consistent with previous separations by our group (Song et al). Andersen et al. (1991) identified the major anthocyanin in purple-fleshed potatoes as petanin (petunidin-3- p-coumaroylrutinoside-5-glucoside). Petunidin derivatives were high in both purple varieties, indicating the possible presence of petanin. Lewis et al. (1998) and Eichhorn and Winterhalter (2005) report the presence of petanin in three varieties of purple-fleshed potatoes, and additional anthocyanins of the same structure as petanin with peonidin and malvidin aglycones. Eichhorn and Winterhalter (2005) also identified peonidin- and malvidin-3-rutinoside-5-glucosides in purple varieties, and Fossen and Andersen (2000) describe petunidin- and malvidin-3-rut-3,5-diglucosides acylated with ferulic acid. The red- fleshed variety in their study contained primarily pelargonidin-3-p-coumaroylrutinoside-5- glucoside (pelanin) and pelargonidin-3-rutinoside-5-glucoside (pg-3-rut-5-glu). Rogriguez- Saona et al. (1998) identified the same pelargonidin derivatives, with the addition of ferulic acid acylation on pg-3-rut-5-glu and pg-3-rut. This literature, along with elution time of major peaks (Figure 4), that the purple-fleshed potatoes in this study likely contain primarily petunidin and malvidin-3-rut or petunidin and malvidin-3-rut-5-glucosides acylated with p-coumaric and ferulic acids. Red-fleshed varieties likely contain the same, with pelargonidin and cyanidin derivatives rather than petunidin and malvidin.

3.5.1.3 Carotenoids

Lutein was detected in all varieties, with values ranging from 0.07 to 0.25 mg/100 g dw. Beta-carotene was not quantifiable in any variety except Covington sweet potato, at 40.3 and 46.4 mg/g in flesh alone and whole potato, respectively.

Table 8. Anthocyanin content of three pigmented potato varieties, expressed by class of anthocyanidin. mg anthocyanidin/100 g dw Total Cyanidins Peonidins Delphinidins Petunidins Malvidins Pelargonidins Anthocyanidins

AR2009- F n.d. 0.72 ± 0.1 7.44 ± 0.8 49.8 ± 4.8 2.24 ± 0.3 n.d. 60.2 ± 1.0 10 W n.d. 0.78 ± 0.1 9.56 ± 0.6 56.0 ± 1.1 2.36 ± 0.1 n.d. 68.7 ± 0.3 F 7.86 ± 0.1 n.d. n.d. n.d. n.d. 25.5 ± 0.91 33.4 ± 0.9 ADR W 15.7 ± 1.6 n.d. n.d. n.d. n.d. 36.7 ± 1.78 52.4 ± 3.1 ADB F 8.39 ± 0.4 14.5 ± 0.8 3.67 ± 0.2 29.9 ± 2.5 1.06 ± 0.1 15.9 ± 1.66 73.4 ± 0.3 W 7.47 ± 0.5 13.5 ± 0.8 3.56 ± 0.3 33.0 ± 2.7 1.25 ± 0.0 15.9 ± 0.33 74.7 ± 1.7

All anthocyanins quantified using cyanidin-3-glucoside equivalents. Each value represents the average of three analytical replicates with standard deviation. “n.d.” used to indicate values too low for quantification. Total anthocyaninss are the sum of each anthocyanidin SIR after quantification. W= whole; F= flesh. ADR= red flesh, red peel; ADB and AR2009-10= purple flesh, purple peel.

Figure 6. Example anthocyanin chromatograms for three varieties of pigmented potato: (1) ADR, (2) ADB, (3) AR2009-10. Examples represent whole, raw samples. Each SIR is one class of anthocyanidn. m/z 287- cyanidin; 301- peonidin; 303- delphinidin; 317- petunidin; 331- malvidin; 271- pelargonidin. Note that SIRs are not to the same scale. The boxes surround acylated anthocyanins (peaks with retention time of ~11 min. or later) which are likely anthocyanidin-3- rutinosides or anthocyanidin-3-rutinoside-5-glucosides acylated with ferulic or p-coumaric acids.

3.5.2 Experiment 2: Chlorogenic acid and Anthocyanin Content through Commercial Processing.

Commercially processed potato products are the primary form of potatoes consumed in the United States. Thus, insight into effects of processing on content and profile of phytochemicals in commercially relevant cultivars will enhance our understanding of the role and potential of processed potato products to contribute to the nutritional quality of the American diet. Existing literature on process stability of main Solanum tuberosum phytochemicals (including phenolic acids and flavonoids) is inconsistent, and the majority of studies conducted use only small-scale lab procedures for processing. As the most abundant phenolic compounds in potatoes, CQAs were the main focus for understanding the effects of commercial processing, and anthocyanins were an additional focus for colored-fleshed varieties. A simple summary of the processed samples used in this study can be found in the methods section (Figure 1).

3.5.2.1 Chlorogenic Acids

In general, total CGAs were lower in peeled and whole potatoes (FNS and FWS) compared to the same raw varieties assayed in Experiment 1 (Tables 7 and 9). This variation is not uncommon and may be due, in part, to harvest year differences, variability in sampling of individual potatoes as well as storage stability in frozen samples. It is important to point out that materials for Experiment 2 were collected from the 2012 harvest and subsequent commercially processed products. By comparison potato samples for Experiment 1 were from 2013. Retention of total CGA through processing from fresh whole potato (FWS) to final products (BF, BFM, BFF, BFFO, BFFF) was moderate to high, ranging from a low of 32% (R. Burbank BFFF) to a high of 85% recovery (ADR BF). Retention was overall lowest for the R. Burbank cultivar (ranging from 32-55%), whereas the colored varieties displayed greater retention through the various forms of processing (ADB 49-72%; ADR 64-85%; AR2 52- 76%). Significant differences in retention were not determined, but this suggests that not only do pigmented varieties have greater concentrations of phenolic acids in raw flesh, but these phenolics may be more stable to processing. This could indicate protective effects of other components present in these varieties, or simply that higher phenolic content is

protective. Some studies which have measured vitamin C, antioxidant activity, and phenolic content through processing do not indicate that a higher ascorbic acid or antioxident content is protective (Navarre et al., 2010; Xu et al., 2009). However, Narita and Inouye (2013) found that stability of 5-CQA was improved with addition of EGCG (epticallocatechin gallate) and ascorbic acid. Nardini et al. (2002) also found that ascorbic acid and EDTA could prevent degradation of phenolic acids during alkaline hydrolysis. In the white R. Burbank variety, total CGAs were significantly lower (p<.05) in all processed products when compared to raw whole, but no significant differences were observed between flesh and processing levels or within processing levels. In all colored- fleshed varieties, BF and BFM treatments did not significantly affect total CQA levels compared to raw flesh (FNS). BFF, BFFO, and BFFF treatments were also all significantly (p<.05) lower in CQAs than FWS or FNS (except ADB BFFO compared to FNS) and in general were lower than BF and BFM treatments, though significance varied. For the ADB variety, BFFF products was significantly (p<.05) lower in CQAs than BF and BFM, but not significantly different from BFF or BFFO. BFF, BFFO, and BFFF products also did not significantly differ from each other for ADB and AR2 varieties. Overall, these results support the notion that thermal treatment by blanching and microwaving may have a modest effect on potato phenolics compared to harsher treatments such as frying and baking. Mäder et al. (2009), whose study also used commercial processing methods, found high retention of phytochemicals throughout blanching, cooking, mashing, and drying. Some processed products (Table 9, Table 10, and additional unpublished data) displayed a slight, but insignificant increase in chlorogenic acids and anthocyanins compared to flesh or other processed methods. While not commonly reported in the literature this has been previously observed (Blessington et al., 2010; Navarre et al., 2010) for microwaving and other forms of processing. These groups attribute these effects to an increase in extractability upon heating, which theoretically could also lead to an increase in digestibility upon consumption. The extraction methods for our study did use an added heating step to enhance the extraction of phenolics from both native and retrograded starch of cooked products, which should have also generally corrected for the effects of heating on extractability. Within the different isoforms of CQAs, it appears that processing most affected levels of 5-CQA. The greater reduction in 5-CQA relative to other isoforms lead to an

increase in the relative proportion of 3-CQA and 4-CQA, which was also observed by Mäder, Rawel, and Kroh (2009).

Figure 7. Example chromatogram of the Norland variety, whole. m/z 353- CQA; m/z 179- caffeic acid. Note that SIRs are not to the same scale.

Figure 8. Total CQAs (sum of averages of 3-,4-, and 5-O-CQAs) quantified in four varieties of commercially processed potatoes. Significant differences determined within each variety (p ≤ .05).

Table 9. CQAs in four varieties of potatoes through various levels of commercial processing. mg polyphenol/100 g dw Sample 3-CQA 4-CQA 5-CQA Total CQA % Ret. From FNS FWS 4.40 ± 0.4a 11.0 ± 1.8b 65.0 ± 7.3c 80.4 ± 9.0A 276% FNS 2.24 ± 0.1a 2.90 ± 0.2a 24.4 ± 4.3b 29.6 ± 4.5AB 100% BF 1.96 ± 0.0a 2.14 ± 0.2a 11.8 ± 4.5b 15.9 ± 4.6B 55% R. Burbank BFM 4.40 ± 0.1a 2.22 ± 0.2a 8.51 ± 4.4b 15.1 ± 4.7B 43% BFF 1.37 ± 1.2a 2.11 ± 0.1a 5.84 ± 0.9b 9.32 ± 0.2B 32% BFFO 2.18 ± 0.0a 2.24 ± 0.1a 6.12 ± 2.0b 10.5 ± 2.2B 36% BFFF n.d. 2.28 ± 0.0a 6.33 ± 1.6b 8.61 ± 5.6B 38% FWS 29.5 ± 2.5a 41.9 ± 2.1b 255 ± 4.8c 327 ± 8.7A 112% FNS 26.0 ± 3.3a 36.8 ± 1.8b 229 ± 3.1c 292 ± 6.5AB 100% BF 24.3 ± 1.2a 33.7 ± 3.3b 189 ± 12c 247 ± 14B 85% ADR BFM 29.5 ± 1.7a 37.6 ± 5.2b 175 ± 30c 242 ± 36B 83% BFF 16.8 ± 0.3a 22.4 ± 1.0a 149 ± 8.9b 188 ± 8.1C 64% BFFO 21.8 ± 1.4a 28.2 ± 1.6a 137 ± 16b 187 ± 16C 64% BFFF 20.2 ± 0.9a 26.6 ± 1.3a 157 ± 14b 204 ± 14BC 70% FWS 21.3 ± 8.6a 36.9 ± 21a 195 ± 49b 253 ± 78AB 119% FNS 17.8 ± 2.6a 29.8 ± 5.7a 165 ± 3.5b 212 ± 12A 100% BF 12.7 ± 1.9a 15.9 ± 5.3b 100 ± 25c 128 ± 32BC 60% ADB BFM 21.3 ± 5.9a 24.2 ± 12a 108 ± 26b 153 ± 44C 72% BFF 9.80 ± 0.9a 12.1 ± 1.6a 81.9 ± 9.0b 104 ± 9.5CD 49% BFFO 12.3 ± 1.4a 16.6 ± 3.5a 83.6 ± 3.3b 112 ± 8.2CD 53% BFFF 12.0 ± 3.4a 15.8 ± 8.1a 91.3 ± 30b 119 ± 42D 56% FWS 7.81 ± 2.6a 28.2 ± 4.9b 312 ± 20c 348 ± 17A 139% FNS 4.14 ± 0.5a 14.6 ± 6.8b 232 ± 38c 251 ± 44B 100% BF 4.49 ± 1.0a 12.5 ± 4.0b 174 ± 12c 191 ± 16C 76% AR2009-10 BFM 7.81 ± 2.5a 17.8 ± 3.3b 154 ± 11c 180 ± 15CD 72% BFF 3.19 ± 0.3a 6.13 ± 1.5a 123 ± 5.2b 133 ± 4.0CD 53% BFFO 6.97 ± 2.3a 12.4 ± 3.5b 119 ± 8.2c 139 ± 13CD 55% BFFF 3.85 ± 0.3a 7.57 ± 0.6b 118 ± 16c 130 ± 16D 52% Each value represents the average of three analytical replicates with standard deviation. Lowercase letters represent significance (p<.05) within a treatment (across a row). Uppercase letter represents significance (p<.05) between treatments (within a variety; down a column). Total CQAs are the sum of the three CQA after quantification. FWS= Flesh with skin; FNS= Flesh without skin; BF= Blanched, frozen; BFM= Blanched, frozen, microwaved; BFF= Blanched, frozen, fried; BFFO= Blanched, fried, frozen, baked; BFFF= Blanched, fried, frozen, fried

3.5.2.2 Anthocyanins

No significant difference was observed in total anthocyanin content within the three varieties (ADR, ADB, and AR2009-10) for commercial processing method. Retention through processing for all varieties ranged from 79% (ADB BFFF) to 129% (ADR BF). While anthocyanins in some foods are highly susceptible to heat, acylated anthocyanins such as those that predominate in colored potatoes, purple carrots, and black currant, for example, have been reported to have greater stability to heating (Brouillard, 1981; Brownmiller et al., 2008; Malien-Aubert et al., 2001; Patras et al., 2010; Sadilova et al., 2006; Song et al., 2013). Other studies have also demonstrated an increase in phytochemicals after processing (see above discussion in section 4.2.1). Overall, anthocyanin content in FWS samples did not differ significantly from FNS for any variety, confirming that anthocyanins are well distributed throughout the flesh rather than being concentrated extensively in the peel. Anthocyanin profile for these varieties differs slightly from that of the same varieties in Experiment 1, which could be due to differences in crop year.

Table 10. Anthocyanins in three pigmented varieties of potato through various levels of commercial processing, expressed by class.

mg anthocyanidin/100 g dw Total % Ret Cyanidins Peonidins Delphinidins Petunidins Malvidins Pelargonidins Anthocyanins from FNS FWS 2.81 ± 0.36 0.67 ± 0.11 n.d. n.d. n.d. 19.4 ± 2.27 22.9 ± 2.66 107% FNS 2.39 ± 0.48 0.22 ± 0.07 n.d. n.d. n.d. 18.7 ± 1.45 21.3 ± 1.98 100% BF 2.73 ± 0.12 0.24 ± 0.02 n.d. n.d. n.d. 24.6 ± 2.79 27.5 ± 2.92 129% ADR BFM 2.34 ± 0.22 0.28 ± 0.03 n.d. n.d. n.d. 23.8 ± 3.51 26.4 ± 3.71 124% BFF 1.76 ± 0.20 0.18 ± 0.01 n.d. n.d. n.d. 20.4 ± 3.53 22.4 ± 3.54 105% BFFO 1.87 ± 0.11 0.23 ± 0.02 n.d. n.d. n.d. 20.2 ± 3.22 22.3 ± 3.33 104% BFFF 1.95 ± 0.13 0.21 ± 0.05 n.d. n.d. n.d. 20.2 ± 3.65 22.3 ± 3.74 105% FWS n.d. n.d. 0.63 ± 0.23 20.1 ± 4.24 2.76 ± 0.49 n.d. 23.4 ± 4.96 109% FNS n.d. n.d. 0.66 ± 0.16 18.8 ± 3.96 2.08 ± 0.54 n.d. 21.5 ± 4.65 100% BF n.d. n.d. 0.72 ± 0.28 18.4 ± 4.82 1.84 ± 0.57 n.d. 20.9 ± 5.67 97% AR2009- BFM n.d. n.d. 0.62 ± 0.28 17.1 ± 4.30 1.58 ± 0.38 n.d. 19.3 ± 4.95 89% 10 BFF n.d. n.d. 0.53 ± 0.10 15.6 ± 1.36 1.50 ± 0.13 n.d. 17.6 ± 1.58 82% BFFO n.d. n.d. 0.56 ± 0.23 15.7 ± 2.71 1.34 ± 0.18 n.d. 17.6 ± 3.11 82% BFFF n.d. n.d. 0.49 ± 0.09 15.7 ± 1.97 2.00 ± 0.84 n.d. 18.2 ± 1.24 85% FWS 0.64 ± 0.09 5.56 ± 0.18 n.d. 9.40 ± 0.86 n.d. 2.97 ± 0.33 18.6 ± 0.99 100% FNS 0.78 ± 0.19 6.11 ± 0.56 n.d. 9.80 ± 0.52 n.d. 1.94 ± 0.97 18.6 ± 2.05 100% BF 0.71 ± 0.26 5.29 ± 1.59 n.d. 8.71 ± 2.21 n.d. 1.86 ± 0.67 16.6 ± 4.58 89% ADB BFM 0.73 ± 0.22 5.45 ± 1.03 n.d. 8.57 ± 1.60 n.d. 2.28 ± 1.13 17.0 ± 3.67 91% BFF 0.71 ± 0.18 4.98 ± 0.71 n.d. 8.39 ± 1.23 n.d. 2.18 ± 0.74 16.3 ± 2.31 87% BFFO 0.67 ± 0.12 4.79 ± 0.68 n.d. 7.94 ± 1.24 n.d. 1.96 ± 0.53 15.4 ± 2.24 82% BFFF 0.64 ± 0.24 4.55 ± 1.51 n.d. 7.28 ± 2.24 n.d. 2.30 ± 1.09 14.8 ± 4.92 79%

All anthocyanins quantified using cyanidin-3-glucoside equivalents. Each value represents the average of three analytical replicates with standard deviation. “n.d.” used to indicate values too low for quantification. Effect of treatment was not significant for any variety, but effect of variety was significant (p<.05). Total anthocyanins are the sum of each anthocyanidin SIR after quantification. FWS= Flesh with skin; FNS= Flesh without skin; BF= Blanched, frozen; BFM= Blanched, frozen, microwaved; BFF= Blanched, frozen, fried; BFFO= Blanched, fried, frozen, baked; BFFF= Blanched, fried, frozen, fried.

Figure 9. Total anthocyanins (sum of averages of individual anthocyanidins) quantified in three varieties of commercially processed potato. Effect of treatment was not significant for any variety, but effect of variety was significant (p<.05).

3.5.3 Experiment 3: Comparison of Chlorogenic Acids and Beta-Carotene in Fresh and Commercially Produced Potato Products.

Current consumers often regard commercially processed foods as more unhealthy than freshly prepared versions, even when methods and ingredients of preparation are very similar. While the “healthiness” of a food is a multifaceted concept, this portion of the study specifically investigated differences in CQA and carotenoid content between commercially processed and reconstituted and freshly prepared versions of the same products. Beta- carotene, as the primary carotenoid in orange-fleshed sweet potatoes, was chosen for study. In this experiment, five fresh products were prepared by baking and frying/panfrying (except for fresh-style fries, which were only fried) to match five reconstituted commercial products (classic French fries, fresh-style French fries, hash browns, sweet potato fries, and sweet potato wedges). The former three products were all prepared from R. Burbank potatoes, while the latter two were prepared from Covington sweet potatoes.

3.5.3.1 Chlorogenic Acids

Total CQA were significantly greater (p<.05) in freshly prepared fried classic fries and baked or pan-fried hash browns than commercially processed fries and baked or pan- fried hash browns. It is possible that because hash browns have a large surface area to volume ratio, the multiple heating steps sustained from processing to reconstitution have a greater effect on phytochemical retention. Baked classic fries and fresh style fries did not significantly differ between fresh and commercial versions. Fresh and commercially processed fried sweet potato fries and wedges also did not significantly differ in total CQA content. Total CQAs were significantly greater (p<.05) in fresh baked potato wedges (95.4 mg/100 g dw) than in the commercial product (77 mg). However, total CQAs were significantly great (p<.05) in commercially processed baked sweet potato fries compared to the freshly prepared version. Overall, these results suggest that while select differences can be observed, generally, there is not a large difference in phenolic content between freshly prepared and commercial French fries made from the same lot of potatoes. Differences, whether significant or not, were sometimes in favor of commercial processing, and sometimes in favor of fresh preparation. For products like hash browns, it is possible that fresh preparation may better retain phytochemicals as the cycle of heat treatments is reduced for this high surface area product. Because CQA were generally greater in fresh versions of products made from Russet Burbank potatoes, it could be that fresh and commercial processing differentially affect this variety. When interpreting the data, one should keep in mind that potatoes are a highly variable vegetable, and further studies would be needed to conclusively answer the “fresh vs. commercial” question.

Table 11. Chlorogenic acids in freshly prepared and commercially processed products.

mg chlorogenic acid/100 g dw Neochlorogenic Cryptochlorogenic Chlorogenic Total Chlorogenic Sample (3-CQA) (4-CQA) (5-CQA) Acids

B 2.56 ± 0.1 2.54 ± 0.1 7.37 ± 1.0 12.5 ± 1.2 Commercial Classic F 2.50 ± 0.0 2.68 ± 0.0 9.72 ± 0.9 14.9 ± 0.9 Fry Fresh B 3.27 ± 0.5 3.09 ± 0.4 10.2 ± 2.5 16.5 ± 3.4 F 3.97 ± 0.2 4.18 ± 0.3 16.7 ± 1.5 24.8 ± 2.0 Fresh-Style Commercial B 2.85 ± 0.4 3.18 ± 0.4 30.5 ± 7.0 38.1 ± 10 Fry Fresh F 2.03 ± 0.1 3.19 ± 0.3 42.6 ± 6.9 36.9 ± 5.4

B 2.62 ± 0.1 3.42 ± 0.2 39.4 ± 3.0 45.4 ± 3.4 Commercial Sweet F 2.48 ± 0.02 2.86 ± 0.1 31.8 ± 3.6 37.2 ± 3.6 Potato Fry B 2.88 ± 0.03 3.18 ± 0.2 21.6 ± 2.6 27.7 ± 2.7 Fresh F 2.06 ± 0.1 2.54 ± 0.1 27.3 ± 3.3 31.9 ± 3.3 B 4.12 ± 0.2 6.04 ± 0.3 67.0 ± 2.2 77.2 ± 2.4 Commercial Sweet F 3.86 ± 0.5 5.13 ± 0.2 71.6 ± 4.5 80.6 ± 5.2 Potato B 6.09 ± 0.6 11.0 ± 0.3 118 ± 3.3 135 ± 3.6 Wedge Fresh F 3.43 ± 0.1 4.47 ± 0.2 83.7 ± 9.3 91.6 ± 10 B 2.60 ± 0.1 2.86 ± 0.1 3.08 ± 0.2 8.54 ± 0.4 Commercial Hash F 2.64 ± 0.03 2.67 ± 0.1 3.62 ± 0.2 8.93 ± 0.3

Browns B 3.53 ± 0.02 3.58 ± 0.1 7.00 ± 0.2 14.1 ± 0.3 Fresh F 3.74 ± 0.04 3.91 ± 0.1 7.68 ± 0.3 15.3 ± 0.2

Each value represents the average of three analytical replicates with standard deviation. Total CQAs are the sum of the three CQAs after quantification. M= commercial sample; P= fresh sample. B= baked; F= Fried.

Figure 10. Total CQAs (sum of averages of 3-,4-, and 5-O-CQA) compared in commercial and fresh products from Russet Burbank potatoes. Significant differences determined between commercially and freshly prepared products are designated by different letter within bar (p ≤ .05).

Figure 11. Total CQAs (sum of averages of 3-,4-, and 5-O-CQA) compared in commercial and fresh products from Covington sweet potatoes. Significant differences determined between commercially and freshly prepared products are designated by a different letter within bar (p ≤ .05).

3.5.3.2 Beta-carotene

Beta-carotene content did not significantly differ between any fresh and commercial sweet potato product except for baked sweet potato wedges, where the commercial product had significantly greater levels of beta-carotene (30 mg/100 g dw and 25 mg/100 g dw, respectively). As previously mentioned, this single difference likely represents an anomaly, not a rule, and overall it appears that beta-carotene content does not significantly differ between fresh and commercial products. Raw Covington sweet potato contained 40.3 ± 2.4 and 46.5 ± 5.7 mg beta-carotene/100 g dw in flesh and whole, respectively. This indicates retention ranging from 59-74% throughout commercial and fresh products. Previous studies have shown similar moderate retention of carotenoids in processed sweet potato products (Berni et al., 2015; Donado-Pestana et al., 2012; van Jaarsveld et al., 2006), though literature directly comparing fresh and commercial products could not be found.

Figure 12. Beta-carotene content in fresh and commercial products. Significant differences determined between commercially and freshly prepared products are designated by a different letter within bar (p ≤ .05).

Conclusions

This study demonstrates that nine commercial Solanum tuberosum cultivars contain high levels of CQAs (3-,4-, and 5- CQA), with 5-CQA comprising the majority of total chlorogenic isomers. Pigmented varieties ADR, ADB, and AR2009-10 contained greater levels of chlorogenic acids than white/yellow-fleshed varieties, in addition to acylated anthocyanins. Retention of CQAs through commercial processing appeared to be greater for pigmented varieties than white R. Burbank, and retention of anthocyanins was high. While white/yellow-fleshed varieties contribute phytochemicals to the diet, this study highlights the potential for pigmented potatoes to contribute greater levels, especially if retention after commercial processing is better. Use of whole, rather than peeled, potato in fresh or commercial applications will also contribute greater levels of phytochemicals to the diet. In general, commercial microwaving and blanching resulted in better retention of chlorogenic acids than frying and subsequent baking or frying, though the latter processes still resulted in moderate retention in pigmented varieties. In general, freshly prepared and commercially processed products were comparable in chlorogenic acid or beta-carotene content with some exceptions, suggesting that fresh and commercial products can provide similar levels of phytochemicals to the diet.

CHAPTER 4. GENERAL FINDINGS AND FUTURE DIRECTIONS

The overall objective of this research was to investigate phytochemical content in commercially relevant cultivars and determine the effects of commercial and fresh processing on phytochemical content. To achieve this objective, three experiments with separate aims were conducted. Experiment (Aim) 1 was used to determine phytochemical content in fresh commercially relevant potato varieties. In experiment (Aim) 2 we determined the extent to which key phenolics including chlorogenic acid and anthocyanins are recovered through commercial processing. In experiment (Aim) 3 we compared the impact of fresh preparation to commercial processing on chlorogenic acid and beta- carotene recovery. In regards to experiment 1, the nine potato cultivars and one sweet potato cultivar used in this study all contained levels of phytochemicals comparable or greater than other common fruits and vegetables, such as apples, peaches, and carrots. Pigmented varieties contain chlorogenic acids (318-953 mg/100 g dw) similar to that of Robusta coffee (~375 mg/100 g dw) and highbush blueberries (~655 mg/100 g dw), both high-phenolic foods (Rothwell et al., 2013). For all potato cultivars, chlorogenic acids (3-, 4-, and 5-CQA acids) were the primary phytochemicals analyzed. As expected, 5-CQA was the primary CQA in both whole and flesh of these cultivars. Whole potatoes generally contained significantly greater levels of CQAs than flesh (though the ratio varied) and anthocyanins did not follow the same pattern. Pigmented potatoes contained greater (p<0.05) levels of CQAs than white/yellow potatoes. In addition, the non-significant differences between CQAs in whole and flesh of pigmented varieties indicate that peeling pigmented varieties can still result in high-phenolic products, while less likely for white/yellow varieties assessed in this study. All of these findings are consistent with previous research (Summarized in Section 1.5). Though there are many existing studies on the phytochemicals in potatoes, generally the small number of varieties included within one study often makes comparison difficult due to differences in research methodology.

Experiment 2 revealed low to moderate process stability of chlorogenic acids in processed potato products, which is consistent with some existing literature and contrasting to others who have demonstrated either very poor (as low as 0%) or very high retention (>500%) upon heat treatment (Blessington et al., 2010; Dao and Friedman, 1992; Deusser et al., 2012; Navarre et al., 2010). Some methods of processing (microwaving and blanching) appear to be gentler on phytochemicals present in these varieties as compared to par-frying, frying, and baking. The effects of processing varied by cultivar. Not only did white-fleshed R. Burbank contain lower levels of CQAs in its raw state, it retained fewer CQAs through processing than its pigmented counterparts. This research suggests that whole pigmented commercially relevant varieties offer more phytochemical potential in the raw state and also may be more stable to degradation through processing than traditional commercial varieties such as R. Burbank and Bintje. Potato anthocyanins displayed high stability to heat processing in all forms, which is likely due to their acylated nature. In experiment 3, some fresh products (pan-fried and baked hash browns, fried classic fries, and baked sweet potato wedges) were significantly higher in CQAs (p<.05) than the commercial versions. However, commercial baked wedges were higher in beta-carotene than fresh baked wedges and commercial fries were higher in CQAs. In general commercial products compared favorably to fresh products in chlorogenic acid and beta-carotene content. Overall, this study found wide variety in phytochemical content of commercially relevant cultivars. Certain popular cultivars used in the processing industry, such as R. Burbank and Innovator, while having beneficial functional characteristics, do not deliver as high a level of phytochemicals as may be desired. Varieties higher in phytochemicals (especially pigmented varieties) may better maximize the health potential of potato products. It is encouraging that pigmented varieties displayed moderate retention of phytochemicals through processing, however, these results do not necessarily extend to other varieties (especially white and yellow-fleshed). Additional studies on phytochemical content and process stability in commercially relevant high-phenolic varieties can guide industry and fresh markets on variety usage. This research has not addressed micronutrients in these commercial varieties, and it obviously did not evaluate consumer acceptance of pigmented potato products. While this study focused on phytochemicals, additional studies on micronutrient content and

stability through processing (and their interactions with phytochemicals) would provide valuable data. Potatoes are naturally highly variable in micronutrient and phytochemical content (Section 1.5.4), which can be affected by many factors from growth to harvest, storage, and processing. Additional studies are needed which control all of these variables from farm to manufacturing facility and beyond into the research laboratory, and these studies should incorporate commercial processing to better relate to the American diet. Further understanding of the types and conditions of processing that better retain potato phytochemicals and the mechanisms by which they do so can also be used to enhance the quality of commercially processed (and fresh) products. This is the first known study directly comparing phytochemical content in multiple fresh and commercial products. While this data suggest that fresh and commercial products are likely comparable in retention of phytochemicals and thus may provide similar dietary levels of these health promoting compounds, additional highly controlled studies including more varieties can improve understanding on the “fresh vs. commercial” question. In addition, the extent to which bioavailability of phytochemicals may be modified by extensive commercial processing relative to fresh preparation is unknown. The results of this study are important for understanding effects of processing on commercial cultivars as well as the differences between those cultivars, but additional research is needed to elucidate reasons that literature on processing and polyphenols yields such vastly different results (even when the same varieties are used). In addition, while understanding phytochemical retention in processed potato products is important, bioavailability is another key element to understanding the overall impact of these compounds on health. In vitro and in vivo research should assess changes in polyphenol bioavailability that occur with processing, including a comparison of different types of processing. Some research has demonstrated an effect of polyphenols on starch bioavailability (Section 1.6.5), and the reverse could also be true. In regards to anthocyanins, existing literature focuses largely on the process stability of acylated anthocyanins in purple-fleshed sweet potato and other root vegetables, and more research also is needed on polyphenol composition through processing in pigmented Solanum tuberosum varieties. Research is additionally lacking regarding potato anthocyanin bioavailability.

LIST OF REFERENCES

2015 Dietary Guidelines Advisory Committee, 2015. Scientific Report of the 2015 Dietary Guidelines Advisory Committee. U.S. Dept. of Health and Human Services and U.S. Dept. of Agriculture. Agriculture and Horticulture Development Board: Potato Council, 2012. Other Varieties Chart [WWW Document]. URL https://www.lovepotatoes.co.uk/other-varieties- chart (accessed 12.18.14). Aguilera, J. m., Gloria-Hernandez, H., 2000. Oil absorption during frying of frozen parfried potatoes. J. Food Sci. 65, 476–479. doi:10.1111/j.1365-2621.2000.tb16031.x Akash, M.S.H., Rehman, K., Chen, S., 2014. Effects of coffee on type 2 diabetes mellitus. Nutrition 30, 755–763. doi:10.1016/j.nut.2013.11.020 Amorati, R., Valgimigli, L., 2015. Advantages and limitations of common testing methods for antioxidants. Free Radic. Res. 1–17. doi:10.3109/10715762.2014.996146 Amrein, T.M., Bachmann, S., Noti, A., Biedermann, M., Barbosa, M.F., Biedermann-Brem, S., Grob, K., Keiser, A., Realini, P., Escher, F., Amadó, R., 2003. Potential of acrylamide formation, sugars, and free asparagine in potatoes: a comparision of cultivars and farming systems. J. Agric. Food Chem. 51, 5556–5560. doi:10.1021/jf034344v Andersen, Ø.M., Opheim, S., Aksnes, D.W., Frøystein, N.Å., 1991. Structure of petanin, an acylated anthocyanin isolated from solanum tuberosum, using homo-and hetero- nuclear two-dimensional nuclear magnetic resonance techniques. Phytochem. Anal. 2, 230–236. doi:10.1002/pca.2800020510 Andre, C.M., Ghislain, M., Bertin, P., Oufir, M., del Rosario Herrera, M., Hoffmann, L., Hausman, J.-F., Larondelle, Y., Evers, D., 2007a. Andean potato cultivars (Solanum tuberosum L.) as a source of antioxidant and mineral micronutrients. J. Agric. Food Chem. 55, 366–378. doi:10.1021/jf062740i Andre, C.M., Oufir, M., Guignard, C., Hoffmann, L., Hausman, J.-F., Evers, D., Larondelle, Y., 2007b. Antioxidant profiling of native andean potato tubers (Solanum tuberosum L.) reveals cultivars with high levels of β-carotene, α-tocopherol, chlorogenic acid, and petanin. J. Agric. Food Chem. 55, 10839–10849. doi:10.1021/jf0726583 Andre, C.M., Schafleitner, R., Guignard, C., Oufir, M., Aliaga, C.A.A., Nomberto, G., Hoffmann, L., Hausman, J.-F., Evers, D., Larondelle, Y., 2009. Modification of the health- promoting value of potato tubers field grown under drought stress: emphasis on dietary antioxidant and glycoalkaloid contents in five native andean cultivars (Solanum tuberosum L.). J. Agric. Food Chem. 57, 599–609. doi:10.1021/jf8025452 Andrikopoulos, N.K., Dedoussis, G.V.Z., Falirea, A., Kalogeropoulos, N., Hatzinikola, H.S., 2002. Deterioration of natural antioxidant species of vegetable edible oils during the domestic deep-frying and pan-frying of potatoes. Int. J. Food Sci. Nutr. 53, 351–363. doi:10.1080/09637480220138098

Antolovich, M., Prenzler, P., Robards, K., Ryan, D., 2000. Sample preparation in the determination of phenolic compounds in fruits. Analyst 125, 989–1009. doi:10.1039/B000080I Arvanitoyannis, I.S., Vaitsi, O., Mavromatis, A., 2008. Potato: a comparative study of the effect of cultivars and cultivation conditions and genetic modification on the physico-chemical properties of potato tubers in conjunction with multivariate analysis towards authenticity. Crit. Rev. Food Sci. Nutr. 48, 799–823. doi:10.1080/10408390701691059 Atkinson, F.S., Foster-Powell, K., Brand-Miller, J.C., 2008. International Tables of Glycemic Index and Glycemic Load Values: 2008. Diabetes Care 31, 2281–2283. doi:10.2337/dc08-1239 Augustin, J., 1975. Variations in the Nutritional Composition of Fresh Potatoes. J. Food Sci. 40, 1295–1299. doi:10.1111/j.1365-2621.1975.tb01076.x Augustin, J., Johnson, S.R., Teitzel, C., True, R.H., Hogan, J.M., Toma, R.B., Shaw, R.L., Deutsch, R.M., 1978. Changes in the nutrient composition of potatoes during home preparation: II. Vitamins. Am. Potato J. 55, 653–662. doi:10.1007/BF02852138 Barros, F., Awika, J.M., Rooney, L.W., 2012. Interaction of tannins and other sorghum phenolic compounds with starch and effects on in vitro starch digestibility. J. Agric. Food Chem. 60, 11609–11617. doi:10.1021/jf3034539 Bassaganya-Riera, J., DiGuardo, M., Viladomiu, M., de Horna, A., Sanchez, S., Einerhand, A.W.C., Sanders, L., Hontecillas, R., 2011. Soluble fibers and resistant starch ameliorate disease activity in interleukin-10-deficient mice with inflammatory bowel disease. J. Nutr. 141, 1318–1325. doi:10.3945/jn.111.139022 Bengtsson, A., Larsson Alminger, M., Svanberg, U., 2009. In vitro bioaccessibility of β- Carotene from heat-processed orange-fleshed sweet potato. J. Agric. Food Chem. 57, 9693–9698. doi:10.1021/jf901692r Berger, K.G., Idris, N.A., 2005. Formulation of zero-trans acid shortenings and margarines and other food fats with products of the oil palm. J. Am. Oil Chem. Soc. 82, 775–782. doi:10.1007/s11746-005-1143-9 Berni, P., Chitchumroonchokchai, C., Canniatti-Brazaca, S.G., De Moura, F.F., Failla, M.L., 2015. Comparison of content and in vitro bioaccessibility of provitamin A carotenoids in home cooked and commercially processed orange fleshed sweet potato (Ipomea batatas Lam). Plant Foods Hum. Nutr. Dordr. Neth. 70, 1–8. doi:10.1007/s11130-014-0458-1 Bertoft, E., Blennow, A., 2009. Chapter 4 - Structure of Potato Starch, in: Singh, J., Kaur, L. (Eds.), Advances in Potato Chemistry and Technology. Academic Press, San Diego, pp. 83–98. Betteridge, D.J., 2000. What is oxidative stress? Metabolism, Advances in Oxidative Stress Proceedings of an “Expert Session” held on the Occasion of the Annual Meeting of the European Association for the study of Diabetes 49, 3–8. doi:10.1016/S0026- 0495(00)80077-3 Blessington, T., Nzaramba, M.N., Scheuring, D.C., Hale, A.L., Reddivari, L., Jr, J.C.M., 2010. Cooking Methods and Storage Treatments of Potato: Effects on Carotenoids, Antioxidant Activity, and Phenolics. Am. J. Potato Res. 87, 479–491. doi:10.1007/s12230-010-9150-7 Bogani, P., Galli, C., Villa, M., Visioli, F., 2007. Postprandial anti-inflammatory and antioxidant effects of extra virgin olive oil. Atherosclerosis 190, 181–186. doi:10.1016/j.atherosclerosis.2006.01.011

Bornet, F.R.J., Jardy-Gennetier, A.-E., Jacquet, N., Stowell, J., 2007. Glycaemic response to foods: impact on satiety and long-term weight regulation. Appetite 49, 535–553. doi:10.1016/j.appet.2007.04.006 Bouchon, P., 2009. Understanding oil absorption during deep-fat frying. Adv. Food Nutr. Res. 57, 209–234. doi:10.1016/S1043-4526(09)57005-2 Bouchon, P., Aguilera, J.M., Pyle, D.L., 2003. Structure Oil-Absorption Relationships During Deep-Fat Frying. J. Food Sci. 68, 2711–2716. doi:10.1111/j.1365- 2621.2003.tb05793.x Bovell-Benjamin, A.C., 2007. Sweet potato: a review of its past, present, and future role in human nutrition. Adv. Food Nutr. Res. 52, 1–59. doi:10.1016/S1043- 4526(06)52001-7 Bradshaw, J., 2007. Potato Breeding Strategy, in: Potato Biology and Biotechnology: Advances and Perspectives: Advances and Perspectives. Elsevier, pp. 157–177. Bradshaw, J.E., Bonierbale, M., 2010. Potatoes, in: Bradshaw, J.E. (Ed.), Root and Tuber Crops, Handbook of Plant Breeding. Springer New York, pp. 1–52. Bradshaw, J.E., Ramsay, G., 2009. Chapter 1 - Potato Origin and Production, in: Singh, J., Kaur, L. (Eds.), Advances in Potato Chemistry and Technology. Academic Press, San Diego, pp. 1–26. Brand, J.C., Nicholson, P.L., Thorburn, A.W., Truswell, A.S., 1985. Food processing and the glycemic index. Am. J. Clin. Nutr. 42, 1192–1196. Brat, P., Georgé, S., Bellamy, A., Chaffaut, L.D., Scalbert, A., Mennen, L., Arnault, N., Amiot, M.J., 2006. Daily Polyphenol Intake in France from Fruit and Vegetables. J. Nutr. 136, 2368–2373. Breithaupt, D.E., Bamedi, A., 2002. Carotenoids and Carotenoid Esters in Potatoes (Solanum tuberosum L.): New Insights into an Ancient Vegetable. J. Agric. Food Chem. 50, 7175–7181. doi:10.1021/jf0257953 Brierley, E.R., Bonner, P.L.R., Cobb, A.H., 1996. Factors Influencing the Free Amino Acid Content of Potato (Solanum tuberosumL) Tubers during Prolonged Storage. J. Sci. Food Agric. 70, 515–525. doi:10.1002/(SICI)1097-0010(199604)70:4<515::AID- JSFA529>3.0.CO;2-P Brouillard, R., 1981. Origin of the exceptional colour stability of the Zebrina anthocyanin. Phytochemistry 20, 143–145. doi:10.1016/0031-9422(81)85234-X Brown, C., Moore, M., Ashok, A., Boge, W., Yang, C.-P., 2005. Genetic Variation of Mineral Content in Potato and Nutritional Considerations. Presented at the 44th Annual Washington State Potato Conference, Moses Lake, WA. Brown, C.R., 2005. Antioxidants in potato. Am. J. Potato Res. 82, 163–172. doi:10.1007/BF02853654 Brown, C.R., Wrolstad, R., Durst, R., Yang, C.-P., Clevidence, B., 2003. Breeding studies in potatoes containing high concentrations of anthocyanins. Am. J. Potato Res. 80, 241– 249. doi:10.1007/BF02855360 Brownmiller, C., Howard, L. r., Prior, R. l., 2008. Processing and Storage Effects on Monomeric Anthocyanins, Percent Polymeric Color, and Antioxidant Capacity of Processed Blueberry Products. J. Food Sci. 73, H72–H79. doi:10.1111/j.1750- 3841.2008.00761.x Burgos, G., Muñoa, L., Sosa, P., Bonierbale, M., Felde, T. zum, Díaz, C., 2013. In vitro Bioaccessibility of Lutein and Zeaxanthin of Yellow Fleshed Boiled Potatoes. Plant Foods Hum. Nutr. 68, 385–390. doi:10.1007/s11130-013-0381-x Burton, W.G., 1989. The potato. Longman Scientific & Technical.

Bushway, R.J., Savage, S.A., Ferguson, B.S., 1987. Inhibition of acetyl cholinesterase by solanaceous glycoalkaloids and alkaloids. Am. Potato J. 64, 409–413. doi:10.1007/BF02853703 Camire, M.E., Kubow, S., Donnelly, D.J., 2009. Potatoes and Human Health. Crit. Rev. Food Sci. Nutr. 49, 823–840. doi:10.1080/10408390903041996 Chen, Y.-Y., Lai, M.-H., Hung, H.-Y., Liu, J.-F., 2013. Sweet potato [Ipomoea batatas (L.) Lam. “Tainong 57”] starch improves insulin sensitivity in high-fructose diet-fed rats by ameliorating adipocytokine levels, pro-inflammatory status, and insulin signaling. J. Nutr. Sci. Vitaminol. (Tokyo) 59, 272–280. Chun, J., Lee, J., Ye, L., Exler, J., Eitenmiller, R.R., 2006. Tocopherol and tocotrienol contents of raw and processed fruits and vegetables in the United States diet. J. Food Compos. Anal. 19, 196–204. doi:10.1016/j.jfca.2005.08.001 Chun, O.K., Kim, D.-O., Smith, N., Schroeder, D., Han, J.T., Lee, C.Y., 2005. Daily consumption of phenolics and total antioxidant capacity from fruit and vegetables in the American diet. J. Sci. Food Agric. 85, 1715–1724. doi:10.1002/jsfa.2176 Cisneros-Zevallos, L., 2003. The Use of Controlled Postharvest Abiotic Stresses as a Tool for Enhancing the Nutraceutical Content and Adding-Value of Fresh Fruits and Vegetables. J. Food Sci. 68, 1560–1565. doi:10.1111/j.1365-2621.2003.tb12291.x Cohen, R., Schwartz, B., Peri, I., Shimoni, E., 2011. Improving Bioavailability and Stability of Genistein by Complexation with High-Amylose Corn Starch. J. Agric. Food Chem. 59, 7932–7938. doi:10.1021/jf2013277 Collier, G., O’Dea, K., 1983. The effect of coingestion of fat on the glucose, insulin, and gastric inhibitory polypeptide responses to carbohydrate and protein. Am. J. Clin. Nutr. 37, 941–944. Cotton, P.A., Subar, A.F., Friday, J.E., Cook, A., 2004. Dietary sources of nutrients among US adults, 1994 to 1996. J. Am. Diet. Assoc. 104, 921–930. doi:10.1016/j.jada.2004.03.019 Crowell, E.F., McGrath, J.M., Douches, D.S., 2007. Accumulation of vitamin E in potato (Solanum tuberosum) tubers. Transgenic Res. 17, 205–217. doi:10.1007/s11248- 007-9091-1 Crozier, A., Jaganath, I., Clifford, M.N., 2009. Dietary phenolics: chemistry, bioavailability and effects on health. R. Soc. Chem. 26, 1001–1043. Dale, M., Griffiths, D.W., Todd, D.T., 2003. Effects of genotype, environment, and postharvest storage on the total ascorbate content of potato (Solanum tuberosum) Tubers. J. Agric. Food Chem. 51, 244–248. Daniel, D.R., Thompson, L.D., Shriver, B.J., Wu, C.-K., Hoover, L.C., 2005. Nonhydrogenated Cottonseed Oil Can Be Used as a Deep Fat Frying Medium to Reduce Trans-Fatty Acid Content in French Fries. J. Am. Diet. Assoc. 105, 1927–1932. doi:10.1016/j.jada.2005.09.029 Dao, L., Friedman, M., 1992. Chlorogenic acid content of fresh and processed potatoes determined by ultraviolet spectrophotometry. J. Agric. Food Chem. 40, 2152–2156. Dawidowicz, A.L., Typek, R., 2014. Transformation of 5-O-Caffeoylquinic Acid in Blueberries during High-Temperature Processing. J. Agric. Food Chem. 62, 10889–10895. doi:10.1021/jf503993q Decker, E.A., Ferruzzi, M.G., 2013. Innovations in food chemistry and processing to enhance the nutrient profile of the white potato in all forms. Adv. Nutr. Bethesda Md 4, 345S– 50S. doi:10.3945/an.112.003574

Del Mar Verde Méndez, C., Rodríguez Delgado, M.Á., Rodríguez Rodríguez, E.M., Díaz Romero, C., 2004. Content of Free Phenolic Compounds in Cultivars of Potatoes Harvested in Tenerife (Canary Islands). J. Agric. Food Chem. 52, 1323–1327. doi:10.1021/jf0345595 Del Rio, D., Borges, G., Crozier, A., 2010. Berry flavonoids and phenolics: bioavailability and evidence of protective effects. Br. J. Nutr. 104, S67–S90. doi:10.1017/S0007114510003958 Desborough, S.L., Liener, I.E., Lulai, E.C., 1981. The nutritional quality of potato protein from intraspecific hybrids. Plant Foods Hum. Nutr. 31, 11–20. doi:10.1007/BF01093884 Deshpande, S.S., Salunkhe, D.K., 1982. Interactions of Tannic Acid and Catechin with Legume Starches. J. Food Sci. 47, 2080–2081. doi:10.1111/j.1365-2621.1982.tb12956.x Deusser, H., Guignard, C., Hoffmann, L., Evers, D., 2012. Polyphenol and glycoalkaloid contents in potato cultivars grown in Luxembourg. Food Chem. 135, 2814–2824. doi:10.1016/j.foodchem.2012.07.028 De Wilde, T., De Meulenaer, B., Mestdagh, F., Govaert, Y., Vandeburie, S., Ooghe, W., Fraselle, S., Demeulemeester, K., Van Peteghem, C., Calus, A., Degroodt, J.-M., Verhé, R., 2005. Influence of Storage Practices on Acrylamide Formation during Potato Frying. J. Agric. Food Chem. 53, 6550–6557. doi:10.1021/jf050650s Dietary Guidelines Advisory Committe, 2010. Report of the Dietary Guidelines Advisory Committee on the Dietary Guidelines for Americans, 2010. US Dept. of Agriculture. Dilworth, L.L., Omoruyi, F.O., Asemota, H.N., 2007. In vitro availability of some essential minerals in commonly eaten processed and unprocessed Caribbean tuber crops. BioMetals 20, 37–42. doi:10.1007/s10534-006-9012-4 Donado-Pestana, C.M., Mastrodi Salgado, J., de Oliveira Rios, A., dos Santos, P.R., Jablonski, A., 2012. Stability of carotenoids, total phenolics and in vitro antioxidant capacity in the thermal processing of orange-fleshed sweet potato (Ipomoea batatas Lam.) cultivars grown in Brazil. Plant Foods Hum. Nutr. Dordr. Neth. 67, 262–270. doi:10.1007/s11130-012-0298-9 Dörmann, P., 2007. Functional diversity of tocochromanols in plants. Planta 225, 269–276. doi:10.1007/s00425-006-0438-2 Dresser, K., 2007. Potato Primer. Drewnowski, A., 1998. Energy Density, Palatability, and Satiety: Implications for Weight Control. Nutr. Rev. 56, 347–353. doi:10.1111/j.1753-4887.1998.tb01677.x Ducreux, L.J.M., Morris, W.L., Hedley, P.E., Shepherd, T., Davies, H.V., Millam, S., Taylor, M.A., 2005. Metabolic engineering of high carotenoid potato tubers containing enhanced levels of β-carotene and lutein. J. Exp. Bot. 56, 81–89. doi:10.1093/jxb/eri016 DuPont, A.W., DuPont, H.L., 2011. The intestinal microbiota and chronic disorders of the gut. Nat. Rev. Gastroenterol. Hepatol. 8, 523–531. doi:10.1038/nrgastro.2011.133 Edwards, C.S., 1845. Improvement in preserving potatoes. US4337 A. Eichhorn, S., Winterhalter, P., 2005. Anthocyanins from pigmented potato (Solanum tuberosum L.) varieties. Food Res. Int., Third International Congress on Pigments in Food Third International Congress on Pigments in Food 38, 943–948. doi:10.1016/j.foodres.2005.03.011 Ek, K.L., Brand-Miller, J., Copeland, L., 2012. Glycemic effect of potatoes. Food Chem., Advances in Potato Chemistry, Nutrition and Technology 133, 1230–1240. doi:10.1016/j.foodchem.2011.09.004 Englyst, H.N., Cummings, J.H., 1987. Digestion of polysaccharides of potato in the small intestine of man. Am. J. Clin. Nutr. 45, 423–431.

Englyst, H.N., Kingman, S.M., Cummings, J.H., 1992. Classification and measurement of nutritionally important starch fractions. Eur. J. Clin. Nutr. 46 Suppl 2, S33–50. Erdmann, D.J., Hebeisen, Y., Lippl, F., Wagenpfeil, S., Schusdziarra, V., 2007. Food intake and plasma ghrelin response during potato-, rice- and pasta-rich test meals. Eur. J. Nutr. 46, 196–203. doi:10.1007/s00394-007-0649-8 Ereifej, K.I., Shibli, R.A., Ajlouni, M.M., Hussein, A., 1998. Mineral contents of whole tubers and selected tissues of ten potato cultivars grown in Jordan. J. Food Sci. Technol. 35, 55–58. Erk, T., Williamson, G., Renouf, M., Marmet, C., Steiling, H., Dionisi, F., Barron, D., Melcher, R., Richling, E., 2012. Dose-dependent absorption of chlorogenic acids in the small intestine assessed by coffee consumption in ileostomists. Mol. Nutr. Food Res. 56, 1488–1500. doi:10.1002/mnfr.201200222 Ezekiel, R., Singh, N., Sharma, S., Kaur, A., 2013. Beneficial phytochemicals in potato — a review. Food Res. Int., Stability of phytochemicals during processing 50, 487–496. doi:10.1016/j.foodres.2011.04.025 Failla, M.L., Chitchumronchokchai, C., Ferruzzi, M.G., Goltz, S.R., Campbell, W.W., 2014. Unsaturated fatty acids promote bioaccessibility and basolateral secretion of carotenoids and α-tocopherol by Caco-2 cells. Food Funct. 5, 1101–1112. doi:10.1039/c3fo60599j Failla, M.L., Thakkar, S.K., Kim, J.Y., 2009. In vitro bioaccessibility of beta-carotene in orange fleshed sweet potato (Ipomoea batatas, Lam.). J. Agric. Food Chem. 57, 10922– 10927. doi:10.1021/jf900415g Falk, J., Munné-Bosch, S., 2010. Tocochromanol functions in plants: antioxidation and beyond. J. Exp. Bot. 61, 1549–1566. doi:10.1093/jxb/erq030 Fan, M.Z., Archbold, T., Lackeyram, D., Liu, Q., Mine, Y., Paliyath, G., 2012. Consumption of guar gum and retrograded high-amylose corn resistant starch increases IL-10 abundance without affecting pro-inflammatory cytokines in the colon of pigs fed a high-fat diet. J. Anim. Sci. 90 Suppl 4, 278–280. doi:10.2527/jas.54006 FAO Trade and Markets Division, 2008. International Year of the Potato: Economy, International Year of the Potato: FAO Factsheets. Food and Agriculture Organization of the United Nations. Farah, A., Monteiro, M., Donangelo, C.M., Lafay, S., 2008. Chlorogenic acids from green coffee extract are highly bioavailable in humans. J. Nutr. 138, 2309–2315. doi:10.3945/jn.108.095554 Farhoosh, R., Kenari, R.E., Poorazrang, H., 2008. Frying Stability of Canola Oil Blended with Palm Olein, Olive, and Corn Oils. J. Am. Oil Chem. Soc. 86, 71–76. doi:10.1007/s11746-008-1315-x Faria, P.A., Fernandes, I., Mateus, N., Calhau, C., 2013. Bioavailability of Anthocyanins, in: Ramawat, K.G., Mérillon, J.-M. (Eds.), Natural Products. Springer Berlin Heidelberg, pp. 2465–2487. Farrell, T.L., Ellam, S.L., Forrelli, T., Williamson, G., 2013. Attenuation of glucose transport across Caco-2 cell monolayers by a polyphenol-rich herbal extract: interactions with SGLT1 and GLUT2 transporters. BioFactors Oxf. Engl. 39, 448–456. doi:10.1002/biof.1090 Fearne, A., 1992. The Great British Potato: A Study of Consumer Demand, Attitudes and Perceptions. Br. Food J. 94, 22–28.

100

Federico, A., Morgillo, F., Tuccillo, C., Ciardiello, F., Loguercio, C., 2007. Chronic inflammation and oxidative stress in human carcinogenesis. Int. J. Cancer J. Int. Cancer 121, 2381– 2386. doi:10.1002/ijc.23192 Feghali, C.A., Wright, T.M., 1997. Cytokines in acute and chronic inflammation. Front. Biosci. J. Virtual Libr. 2, d12–26. Fernandes, G., Velangi, A., Wolever, T.M.S., 2005. Glycemic index of potatoes commonly consumed in North America. J. Am. Diet. Assoc. 105, 557–562. doi:10.1016/j.jada.2005.01.003 Ferruzzi, M.G., 2010. The influence of beverage composition on delivery of phenolic compounds from coffee and tea. Physiol. Behav., Beverages and Health 100, 33–41. doi:10.1016/j.physbeh.2010.01.035 Fillion, L., Henry, C.J.K., 1998. Nutrient losses and gains during frying: a review. Int. J. Food Sci. Nutr. 49, 157–168. doi:10.3109/09637489809089395 Food and Agriculture Organization of the United Nations, 2008a. International Year of the Potato: The Potato. Food and Agriculture Organization of the United Nations, 2008b. International Year of the Potato: Potato World. Foot, R.J., Haase, N.U., Grob, K., Gondé, P., 2007. Acrylamide in fried and roasted potato products: a review on progress in mitigation. Food Addit. Contam. 24 Suppl 1, 37– 46. doi:10.1080/02652030701439543 Fossen, T., Andersen, Ø.M., 2000. Anthocyanins from tubers and shoots of the purple potato, Solanum tuberosum. J. Hortic. Sci. Biotechnol. 75, 360–363. Foster-Powell, K., Holt, S.H., Brand-Miller, J.C., 2002. International table of glycemic index and glycemic load values: 2002. Am. J. Clin. Nutr. 76, 5–56. Friedman, M., 2006. Potato glycoalkaloids and metabolites: roles in the plant and in the diet. J. Agric. Food Chem. 54, 8655–8681. doi:10.1021/jf061471t Friedman, M., Levin, C.E., 2008. Review of methods for the reduction of dietary content and toxicity of acrylamide. J. Agric. Food Chem. 56, 6113–6140. doi:10.1021/jf0730486 Friedman, M., McDonald, G.M., Filadelfi-Keszi, M., 1997. Potato Glycoalkaloids: Chemistry, Analysis, Safety, and Plant Physiology. Crit. Rev. Plant Sci. 16, 55–132. doi:10.1080/07352689709701946 Frossard, E., Bucher, M., Mächler, F., Mozafar, A., Hurrell, R., 2000. Potential for increasing the content and bioavailability of Fe, Zn and Ca in plants for human nutrition. J. Sci. Food Agric. 80, 861–879. doi:10.1002/(SICI)1097-0010(20000515)80:7<861::AID- JSFA601>3.0.CO;2-P Gahlawat, P., Sehgal, S., 1998. Protein and starch digestibilities and mineral availability of products developed from potato, soy and corn flour. Plant Foods Hum. Nutr. Dordr. Neth. 52, 151–160. Galliard, T., 1973. Lipids of potato tubers. 1. Lipid and fatty acid composition of tubers from different varieties of potato. J. Sci. Food Agric. 24, 617–622. doi:10.1002/jsfa.2740240515 García-Alonso, A., Goñi, I., 2000. Effect of processing on potato starch: In vitro availability and glycaemic index. Food Nahr. 44, 19–22. doi:10.1002/(SICI)1521- 3803(20000101)44:1<19::AID-FOOD19>3.0.CO;2-E Garcı́a, M.A., Ferrero, C., Bértola, N., Martino, M., Zaritzky, N., 2002. Edible coatings from cellulose derivatives to reduce oil uptake in fried products. Innov. Food Sci. Emerg. Technol. 3, 391–397. doi:10.1016/S1466-8564(02)00050-4

100

101

Garrett, null, Failla, null, Sarama, null, 2000. Estimation of carotenoid bioavailability from fresh stir-fried vegetables using an in vitro digestion/Caco-2 cell culture model. J. Nutr. Biochem. 11, 574–580. Gentilcore, D., Chaikomin, R., Jones, K.L., Russo, A., Feinle-Bisset, C., Wishart, J.M., Rayner, C.K., Horowitz, M., 2006. Effects of Fat on Gastric Emptying of and the Glycemic, Insulin, and Incretin Responses to a Carbohydrate Meal in Type 2 Diabetes. J. Clin. Endocrinol. Metab. 91, 2062–2067. doi:10.1210/jc.2005-2644 Ghosh, D., Konishi, T., 2007. Anthocyanins and anthocyanin-rich extracts: role in diabetes and eye function. Asia Pac. J. Clin. Nutr. 16, 200–208. Giusti, M.M., Wrolstad, R.E., 2003. Acylated anthocyanins from edible sources and their applications in food systems. Biochem. Eng. J., Advance in Plant Anthocyanin Research and Development 14, 217–225. doi:10.1016/S1369-703X(02)00221-8 Giusti, M.M., Wrolstad, R.E., 1996. Radish Anthocyanin Extract as a Natural Red Colorant for Maraschino Cherries. J. Food Sci. 61, 688–694. doi:10.1111/j.1365- 2621.1996.tb12182.x Global Crop Diversity Trust, FAO Plant Production and Protection Division, 2008. International Year of the Potato: Biodiversity, International Year of the Potato: FAO Factsheets. Food and Agriculture Organization of the United Nations. Golaszewska, B., Zalewski, S., 2001. Optimisation of potato quality in culinary process. Pol. J. Food Nutr. Sci. 1. Goltz, S.R., Ferruzzi, M.G., 2013. Carotenoid Bioavailability: Influence of Dietary Lipid and Fiber, in: Tanumihardjo, S.A. (Ed.), Carotenoids and Human Health, Nutrition and Health. Humana Press, pp. 111–128. Goñi, I., Bravo, L., Larrauri, J.A., Calixto, F.S., 1997. Resistant starch in potatoes deep-fried in olive oil. Food Chem. 59, 269–272. doi:10.1016/S0308-8146(96)00275-0 Gonthier, M.-P., Remesy, C., Scalbert, A., Cheynier, V., Souquet, J.-M., Poutanen, K., Aura, A.-M., 2006. Microbial metabolism of caffeic acid and its esters chlorogenic and caftaric acids by human faecal microbiota in vitro. Biomed. Pharmacother. Bioméd. Pharmacothérapie 60, 536–540. doi:10.1016/j.biopha.2006.07.084 Gordon, M.H., Kourkimskå, L., 1995. The effects of antioxidants on changes in oils during heating and deep frying. J. Sci. Food Agric. 68, 347–353. doi:10.1002/jsfa.2740680314 Govindakrishnan, P.M., Haverkort, A.J., 2006. Chapter 6- Ecophysiology and Agronomic Management, in: Gopal, J., Khurana, S.M. (Eds.), Handbook of Potato Production, Improvement, and Postharvest Management. The Haworth Press, Inc. Greiner, T., Bäckhed, F., 2011. Effects of the gut microbiota on obesity and glucose homeostasis. Trends Endocrinol. Metab. TEM 22, 117–123. doi:10.1016/j.tem.2011.01.002 Gulliford, M.C., Bicknell, E.J., Scarpello, J.H., 1989. Differential effect of protein and fat ingestion on blood glucose responses to high- and low-glycemic-index carbohydrates in noninsulin-dependent diabetic subjects. Am. J. Clin. Nutr. 50, 773– 777. Halton, T.L., Willett, W.C., Liu, S., Manson, J.E., Stampfer, M.J., Hu, F.B., 2006. Potato and french fry consumption and risk of type 2 diabetes in women. Am. J. Clin. Nutr. 83, 284–290. Hanhineva, K., Törrönen, R., Bondia-Pons, I., Pekkinen, J., Kolehmainen, M., Mykkänen, H., Poutanen, K., 2010. Impact of Dietary Polyphenols on Carbohydrate Metabolism. Int. J. Mol. Sci. 11, 1365–1402. doi:10.3390/ijms11041365

101

102

Han, J.-S., Kozukue, N., Young, K.-S., Lee, K.-R., Friedman, M., 2004. Distribution of Ascorbic Acid in Potato Tubers and in Home-Processed and Commercial Potato Foods. J. Agric. Food Chem. 52, 6516–6521. doi:10.1021/jf0493270 Harada, K., Kano, M., Takayanagi, T., Yamakawa, O., Ishikawa, F., 2004. Absorption of Acylated Anthocyanins in Rats and Humans after Ingesting an Extract of Ipomoea batatas Purple Sweet Potato Tuber. Biosci. Biotechnol. Biochem. 68, 1500–1507. doi:10.1271/bbb.68.1500 Hassanpana, D., Hassanabad, H., Azizi Chak, S.H., 2011. Evaluation of Cooking Quality Characteristics of Advanced Clones and Potato Cultivars. Am. J. Food Technol. 6, 72– 79. doi:10.3923/ajft.2011.72.79 Hawkes, J.G., 1990. The potato: Evolution, biodiversity and genetic resources. Am. Potato J. 67, 733–735. doi:10.1007/BF03044023 He, J., Giusti, M.M., 2010. Anthocyanins: natural colorants with health-promoting properties. Annu. Rev. Food Sci. Technol. 1, 163–187. doi:10.1146/annurev.food.080708.100754 Henry, C.J.K., Lightowler, H.J., Strik, C.M., Storey, M., 2005. Glycaemic index values for commercially available potatoes in Great Britain. Br. J. Nutr. 94, 917–921. doi:10.1079/BJN20051571 Holt, S.H., Miller, J.C., Petocz, P., Farmakalidis, E., 1995. A satiety index of common foods. Eur. J. Clin. Nutr. 49, 675–690. Hoover, R., 2001. Composition, molecular structure, and physicochemical properties of tuber and root starches: a review. Carbohydr. Polym. 45, 253–267. doi:10.1016/S0144-8617(00)00260-5 Huang, A.S., Tanudjaja, L., Lum, D., 1999. Content of Alpha-, Beta-Carotene, and Dietary Fiber in 18 Sweetpotato Varieties Grown in Hawaii. J. Food Compos. Anal. 12, 147–151. doi:10.1006/jfca.1999.0819 Huang, C., Tang, Y.L., Chen, C.Y., Chen, M.L., Chu, C.H., Hseu, C.T., 2000. The bioavailability of beta-carotene in stir- or deep-fried vegetables in men determined by measuring the serum response to a single ingestion. J. Nutr. 130, 534–540. Huo, T., Ferruzzi, M.G., Schwartz, S.J., Failla, M.L., 2007. Impact of fatty acyl composition and quantity of triglycerides on bioaccessibility of dietary carotenoids. J. Agric. Food Chem. 55, 8950–8957. doi:10.1021/jf071687a Iablokov, V., Sydora, B.C., Foshaug, R., Meddings, J., Driedger, D., Churchill, T., Fedorak, R.N., 2010. Naturally occurring glycoalkaloids in potatoes aggravate intestinal inflammation in two mouse models of inflammatory bowel disease. Dig. Dis. Sci. 55, 3078–3085. doi:10.1007/s10620-010-1158-9 Im, H.W., Suh, B.-S., Lee, S.-U., Kozukue, N., Ohnisi-Kameyama, M., Levin, C.E., Friedman, M., 2008. Analysis of Phenolic Compounds by High-Performance Liquid Chromatography and Liquid Chromatography/Mass Spectrometry in Potato Plant Flowers, Leaves, Stems, and Tubers and in Home-Processed Potatoes. J. Agric. Food Chem. 56, 3341–3349. doi:10.1021/jf073476b Institute of Medicine, 2005. Dietary reference intakes for energy, carbohydrate, fiber, fat, fatty acids, cholesterol, protein, and amino acids. The National Academies. Jai Gopal, S. M. Paul Khurana, 2006. Handbook of Potato Production, Improvement, and Postharvest Management. The Haworth Press, Inc. Jansen, G., Flamme, W., 2006. Coloured potatoes (Solanum Tuberosum L.) – Anthocyanin Content and Tuber Quality. Genet. Resour. Crop Evol. 53, 1321–1331. doi:10.1007/s10722-005-3880-2

102

103

Jansky, S., 2009. Chapter 2 - Breeding, Genetics, and Cultivar Development, in: Singh, J., Kaur, L. (Eds.), Advances in Potato Chemistry and Technology. Academic Press, San Diego, pp. 27–62. Jaquet, M., Rochat, I., Moulin, J., Cavin, C., Bibiloni, R., 2009. Impact of coffee consumption on the gut microbiota: a human volunteer study. Int. J. Food Microbiol. 130, 117–121. doi:10.1016/j.ijfoodmicro.2009.01.011 Jemison, J.M., Sexton, P., Camire, M.E., 2008. Factors Influencing Consumer Preference of Fresh Potato Varieties in Maine. Am. J. Potato Res. 85, 140–149. doi:10.1007/s12230-008-9017-3 Jenkins, D.J., Wolever, T.M., Taylor, R.H., Barker, H., Fielden, H., Baldwin, J.M., Bowling, A.C., Newman, H.C., Jenkins, A.L., Goff, D.V., 1981. Glycemic index of foods: a physiological basis for carbohydrate exchange. Am. J. Clin. Nutr. 34, 362–366. Jiao, J., Xu, J.-Y., Zhang, W., Han, S., Qin, L.-Q., 2015. Effect of dietary fiber on circulating C- reactive protein in overweight and obese adults: a meta-analysis of randomized controlled trials. Int. J. Food Sci. Nutr. 66, 114–119. doi:10.3109/09637486.2014.959898 Kanan, W., Bijlani, R.L., Sachdeva, U., Mahapatra, S.C., Shah, P., Karmarkar, M.G., 1998. Glycaemic and insulinaemic responses to natural foods, frozen foods and their laboratory equivalents. Indian J. Physiol. Pharmacol. 42, 81–89. Kärenlampi, S.O., White, P.J., 2009. Chapter 5 - Potato Proteins, Lipids, and Minerals, in: Singh, J., Kaur, L. (Eds.), Advances in Potato Chemistry and Technology. Academic Press, San Diego, pp. 99–125. Kaspar, K.L., Park, J.S., Brown, C.R., Mathison, B.D., Navarre, D.A., Chew, B.P., 2011. Pigmented Potato Consumption Alters Oxidative Stress and Inflammatory Damage in Men. J. Nutr. 141, 108–111. doi:10.3945/jn.110.128074 Katan, M.B., 2006. Regulation of trans fats: The gap, the Polder, and McDonald’s French fries. Atheroscler. Suppl., First International Symposium on Trans Fatty Acids and Health Rungstedgaard, Rungsted Kyst, Denmark 7, 63–66. doi:10.1016/j.atherosclerosissup.2006.04.013 Kean, E.G., Hamaker, B.R., Ferruzzi, M.G., 2008. Carotenoid bioaccessibility from whole grain and degermed maize meal products. J. Agric. Food Chem. 56, 9918–9926. doi:10.1021/jf8018613 Keijbets, M.J.H., 2008. Potato Processing for the Consumer: Developments and Future Challenges. Potato Res. 51, 271–281. doi:10.1007/s11540-008-9104-3 Keller, C., Escher, F., Solms, J., 1990. Nutrient retention in deep fat frying - case study on chips. Mitteilungen Aus Dem Geb. Leb. Hyg. 81, 68–81. Kenny, O.M., McCarthy, C.M., Brunton, N.P., Hossain, M.B., Rai, D.K., Collins, S.G., Jones, P.W., Maguire, A.R., O’Brien, N.M., 2013. Anti-inflammatory properties of potato glycoalkaloids in stimulated Jurkat and Raw 264.7 mouse macrophages. Life Sci. 92, 775–782. doi:10.1016/j.lfs.2013.02.006 Keukens, E.A.J., de Vrije, T., Fabrie, C.H.J.P., Demel, R.A., Jongen, W.M.F., de Kruijff, B., 1992. Dual specificity of sterol-mediated glycoalkaloid induced membrane disruption. Biochim. Biophys. Acta BBA - Biomembr. 1110, 127–136. doi:10.1016/0005- 2736(92)90349-Q Khanbari, O.S., Thompson, A.K., 1993. Effects of amino acids and glucose on the fry colour of potato crisps. Potato Res. 36, 359–364. doi:10.1007/BF02361803

103

104

Khosravi-Boroujeni, H., Mohammadifard, N., Sarrafzadegan, N., Sajjadi, F., Maghroun, M., Khosravi, A., Alikhasi, H., Rafieian, M., Azadbakht, L., 2012. Potato consumption and cardiovascular disease risk factors among Iranian population. Int. J. Food Sci. Nutr. 63, 913–920. doi:10.3109/09637486.2012.690024 King, J.C., Slavin, J.L., 2013. White Potatoes, Human Health, and Dietary Guidance. Adv. Nutr. Int. Rev. J. 4, 393S–401S. doi:10.3945/an.112.003525 Kirkman, M.A., 2007. Chapter 2 - Global markets for processed potato products, in: Bradshaw, D.V., Gebhardt, C., Govers, F., Mackerron, D.K.L., Taylor, M.A., Ross, H.A. (Eds.), Potato Biology and Biotechnology. Elsevier Science B.V., Amsterdam, pp. 27– 44. Kırca, A., Özkan, M., Cemeroğlu, B., 2007. Effects of temperature, solid content and pH on the stability of black carrot anthocyanins. Food Chem. 101, 212–218. doi:10.1016/j.foodchem.2006.01.019 Kolasa, K.M., 1993. The potato and human nutrition. Am. Potato J. 70, 375–384. doi:10.1007/BF02849118 Kondo, Y., Higashi, C., Iwama, M., Ishihara, K., Handa, S., Mugita, H., Maruyama, N., Koga, H., Ishigami, A., 2012. Bioavailability of vitamin C from mashed potatoes and potato chips after oral administration in healthy Japanese men. Br. J. Nutr. 107, 885–892. doi:10.1017/S0007114511003643 Kondo, Y., Sakuma, R., Ichisawa, M., Ishihara, K., Kubo, M., Handa, S., Mugita, H., Maruyama, N., Koga, H., Ishigami, A., 2014. Potato chip intake increases ascorbic acid levels and decreases reactive oxygen species in SMP30/GNL knockout mouse tissues. J. Agric. Food Chem. 62, 9286–9295. doi:10.1021/jf502587j Kootte, R.S., Vrieze, A., Holleman, F., Dallinga-Thie, G.M., Zoetendal, E.G., de Vos, W.M., Groen, A.K., Hoekstra, J.B.L., Stroes, E.S., Nieuwdorp, M., 2012. The therapeutic potential of manipulating gut microbiota in obesity and type 2 diabetes mellitus. Diabetes Obes. Metab. 14, 112–120. doi:10.1111/j.1463-1326.2011.01483.x Kurilich, A.C., Clevidence, B.A., Britz, S.J., Simon, P.W., Novotny, J.A., 2005. Plasma and Urine Responses Are Lower for Acylated vs Nonacylated Anthocyanins from Raw and Cooked Purple Carrots. J. Agric. Food Chem. 53, 6537–6542. doi:10.1021/jf050570o Lachman, J., Hamouz, K., 2005. Red and purple coloured potatoes as a significant antioxidant source in human nutrition - a review. Plant Soil Environ. - UZPI Czech Repub. Lachman, J., Hamouz, K., Musilová, J., Hejtmánková, K., Kotíková, Z., Pazderů, K., Domkářová, J., Pivec, V., Cimr, J., 2013. Effect of peeling and three cooking methods on the content of selected phytochemicals in potato tubers with various colour of flesh. Food Chem. 138, 1189–1197. doi:10.1016/j.foodchem.2012.11.114 Le Blay, G.M., Michel, C.D., Blottière, H.M., Cherbut, C.J., 2003. Raw potato starch and short- chain fructo-oligosaccharides affect the composition and metabolic activity of rat intestinal microbiota differently depending on the caecocolonic segment involved. J. Appl. Microbiol. 94, 312–320. Lee, K.-R., Kozukue, N., Han, J.-S., Park, J.-H., Chang, E., Baek, E.-J., Chang, J.-S., Friedman, M., 2004. Glycoalkaloids and Metabolites Inhibit the Growth of Human Colon (HT29) and Liver (HepG2) Cancer Cells. J. Agric. Food Chem. 52, 2832–2839. doi:10.1021/jf030526d Leeman, A.M., Bårström, L.M., Björck, I.M., 2005. In vitro availability of starch in heat-treated potatoes as related to genotype, weight and storage time. J. Sci. Food Agric. 85, 751– 756. doi:10.1002/jsfa.2035

104

105

Lee, S.-J., Shin, J.-S., Choi, H.-E., Lee, K.-G., Cho, Y.-W., An, H.-J., Jang, D.S., Jeong, J.-C., Kwon, O.- K., Nam, J.-H., Lee, K.-T., 2014. Chloroform fraction of Solanum tuberosum L. cv Jayoung epidermis suppresses LPS-induced inflammatory responses in macrophages and DSS-induced colitis in mice. Food Chem. Toxicol. Int. J. Publ. Br. Ind. Biol. Res. Assoc. 63, 53–61. doi:10.1016/j.fct.2013.10.040 Lee, S.K., Kader, A.A., 2000. Preharvest and postharvest factors influencing vitamin C content of horticultural crops. Postharvest Biol. Technol. 20, 207–220. doi:10.1016/S0925-5214(00)00133-2 Leo, L., Leone, A., Longo, C., Lombardi, D.A., Raimo, F., Zacheo, G., 2008. Antioxidant Compounds and Antioxidant Activity in “Early Potatoes.” J. Agric. Food Chem. 56, 4154–4163. doi:10.1021/jf073322w Lewis, C.E., Walker, J.R.L., Lancaster, J.E., Sutton, K.H., 1998. Determination of anthocyanins, flavonoids and phenolic acids in potatoes. I: Coloured cultivars of Solanum tuberosum L. J. Sci. Food Agric. 77, 45–57. doi:10.1002/(SICI)1097- 0010(199805)77:1<45::AID-JSFA1>3.0.CO;2-S Liljeberg, H., Bjorck, I., 1998. Delayed gastric emptying rate may explain improved glycaemia in healthy subjects to a starchy meal with added vinegar. Eur. J. Clin. Nutr. 52, 368–371. Linnemann, A.R., Es, A. van, Hartmans, K.J., 1985. Changes in the content of L-ascorbic acid, glucose, fructose, sucrose and total glycoalkaloids in potatoes (cv. Bintje) stored at 7, 16 and 28°C. Potato Res. 28, 271–278. doi:10.1007/BF02357581 Liu, R.H., 2013. Health-promoting components of fruits and vegetables in the diet. Adv. Nutr. Bethesda Md 4, 384S–92S. doi:10.3945/an.112.003517 Liu, S., Willett, W.C., 2002. Dietary glycemic load and atherothrombotic risk. Curr. Atheroscler. Rep. 4, 454–461. doi:10.1007/s11883-002-0050-2 Lloyd, B.J., 2004. Analysis of radiant heating to produce an alternative frying process. North Carolina State University. Lloyd, B.J., Farkas, B.E., Keener, K.M., 2004. Quality Comparison of French Fry Style Potatoes Produced by Oven Heating, Immersion Frying and Controlled Dynamic Radiant Heating. J. Food Process. Preserv. 28, 460–472. doi:10.1111/j.1745- 4549.2004.23075.x Love, S.L., Salaiz, T., Shafii, B., Price, W.J., Mosley, A.R., Thornton, R.E., 2004. Stability of Expression and Concentration of Ascorbic Acid in North American Potato Germplasm. HortScience 39, 156–160. Ludwig DS, 2002. The glycemic index: Physiological mechanisms relating to obesity, diabetes, and cardiovascular disease. JAMA 287, 2414–2423. doi:10.1001/jama.287.18.2414 Lunetta, M., Di Mauro, M., Crimi, S., Mughini, L., 1995. Influence of different cooking processes on the glycaemic response to potatoes in non-insulin dependent diabetic patients. Diabetes Nutr. Metab. 8, 49–53. Mäder, J., Rawel, H., Kroh, L.W., 2009. Composition of Phenolic Compounds and Glycoalkaloids α-Solanine and α-Chaconine during Commercial Potato Processing. J. Agric. Food Chem. 57, 6292–6297. doi:10.1021/jf901066k Maiani, G., Periago Castón, M.J., Catasta, G., Toti, E., Cambrodón, I.G., Bysted, A., Granado- Lorencio, F., Olmedilla-Alonso, B., Knuthsen, P., Valoti, M., Böhm, V., Mayer-Miebach, E., Behsnilian, D., Schlemmer, U., 2009. Carotenoids: Actual knowledge on food sources, intakes, stability and bioavailability and their protective role in humans. Mol. Nutr. Food Res. 53, S194–S218. doi:10.1002/mnfr.200800053

105

106

Malien-Aubert, C., Dangles, O., Amiot, M.J., 2001. Color Stability of Commercial Anthocyanin- Based Extracts in Relation to the Phenolic Composition. Protective Effects by Intra- and Intermolecular Copigmentation. J. Agric. Food Chem. 49, 170–176. doi:10.1021/jf000791o Manach, C., Mazur, A., Scalbert, A., 2005a. Polyphenols and prevention of cardiovascular disease. Curr. Opin. Lipidol. 16, 77–84. Manach, C., Scalbert, A., Morand, C., Rémésy, C., Jiménez, L., 2004. Polyphenols: food sources and bioavailability. Am. J. Clin. Nutr. 79, 727–747. Manach, C., Williamson, G., Morand, C., Scalbert, A., Rémésy, C., 2005b. Bioavailability and bioefficacy of polyphenols in humans. I. Review of 97 bioavailability studies. Am. J. Clin. Nutr. 81, 230S–242S. Man, Y. b. C., Liu, J. l., Jamilah, B., Rahman, R.A., 1999. Quality Changes of Refined-Bleached- Deodorized (rbd) Palm Olein, Soybean Oil and Their Blends During Deep-Fat Frying. J. Food Lipids 6, 181–193. doi:10.1111/j.1745-4522.1999.tb00142.x Martinez-Puig, D., Pérez, J.F., Castillo, M., Andaluz, A., Anguita, M., Morales, J., Gasa, J., 2003. Consumption of raw potato starch increases colon length and fecal excretion of purine bases in growing pigs. J. Nutr. 133, 134–139. Matthäus, B., 2006. Utilization of high-oleic rapeseed oil for deep-fat frying of French fries compared to other commonly used edible oils. Eur. J. Lipid Sci. Technol. 108, 200– 211. doi:10.1002/ejlt.200500249 Mattila, P., Hellström, J., 2007. Phenolic acids in potatoes, vegetables, and some of their products. J. Food Compos. Anal., The essential balance: Risks and benefits in food safety and quality 20, 152–160. doi:10.1016/j.jfca.2006.05.007 Mazza, G., Hung, J., Dench, M.J., 1983. Processing/Nutritional Quality Changes in Potato Tubers During Growth and Long Term Storage. Can. Inst. Food Sci. Technol. J. 16, 39–44. doi:10.1016/S0315-5463(83)72017-1 McGhie, T.K., Walton, M.C., 2007. The bioavailability and absorption of anthocyanins: Towards a better understanding. Mol. Nutr. Food Res. 51, 702–713. doi:10.1002/mnfr.200700092 McGill, C.R., Kurilich, A.C., Davignon, J., 2013. The role of potatoes and potato components in cardiometabolic health: a review. Ann. Med. 45, 467–473. doi:10.3109/07853890.2013.813633 Mehta, U., Swinburn, B., 2001. A Review of Factors Affecting Fat Absorption in Hot Chips. Crit. Rev. Food Sci. Nutr. 41, 133–154. doi:10.1080/20014091091788 Mellema, M., 2003. Mechanism and reduction of fat uptake in deep-fat fried foods. Trends Food Sci. Technol. 14, 364–373. doi:10.1016/S0924-2244(03)00050-5 Mercier, C., Charbonniere, R., Gallant, D., Guilbot, A., 2013. Structural modification of various starches by extrusion cooking with a twin-screw french extruder, in: Polysaccharides in Food. Elsevier, pp. 153–170. Miller, P.E., Lesko, S.M., Muscat, J.E., Lazarus, P., Hartman, T.J., 2010. Dietary patterns and colorectal adenoma and cancer risk: a review of the epidemiological evidence. Nutr. Cancer 62, 413–424. doi:10.1080/01635580903407114 Mills, C.E., Tzounis, X., Oruna-Concha, M.-J., Mottram, D.S., Gibson, G.R., Spencer, J.P.E., 2015. In vitro colonic metabolism of coffee and chlorogenic acid results in selective changes in human faecal microbiota growth. Br. J. Nutr. 113, 1220–1227. doi:10.1017/S0007114514003948

106

107

Mills, J.P., Tumuhimbise, G.A., Jamil, K.M., Thakkar, S.K., Failla, M.L., Tanumihardjo, S.A., 2009. Sweet potato beta-carotene bioefficacy is enhanced by dietary fat and not reduced by soluble fiber intake in Mongolian gerbils. J. Nutr. 139, 44–50. doi:10.3945/jn.108.098947 Miranda, L., Deußer, H., Evers, D., 2013. The impact of in vitro digestion on bioaccessibility of polyphenols from potatoes and sweet potatoes and their influence on iron absorption by human intestinal cells. Food Funct. 4, 1595–1601. doi:10.1039/c3fo60194c Miranda, M.L., Aguilera, J.M., 2006. Structure and Texture Properties of Fried Potato Products. Food Rev. Int. 22, 173–201. doi:10.1080/87559120600574584 Monro, J., Mishra, S., Blandford, E., Anderson, J., Genet, R., 2009. Potato genotype differences in nutritionally distinct starch fractions after cooking, and cooking plus storing cool. J. Food Compos. Anal., International Year of the Potato 22, 539–545. doi:10.1016/j.jfca.2008.11.008 Monteleone, E., Raats, M.M., Mela, D.J., 1997. Perceptions of starchy food dishes: application of the Repertory Grid Method. Appetite 28, 255–265. doi:10.1006/appe.1996.0081 Morales, F., Capuano, E., Fogliano, V., 2008. Mitigation Strategies to Reduce Acrylamide Formation in Fried Potato Products. Ann. N. Y. Acad. Sci. 1126, 89–100. doi:10.1196/annals.1433.051 Mori, K., Asano, K., Tamiya, S., Nakao, T., Mori, M., 2015. Challenges of breeding potato cultivars to grow in various environments and to meet different demands. Breed. Sci. 65, 3–16. doi:10.1270/jsbbs.65.3 Mulinacci, N., Ieri, F., Giaccherini, C., Innocenti, M., Andrenelli, L., Canova, G., Saracchi, M., Casiraghi, M.C., 2008. Effect of Cooking on the Anthocyanins, Phenolic Acids, Glycoalkaloids, and Resistant Starch Content in Two Pigmented Cultivars of Solanum tuberosum L. J. Agric. Food Chem. 56, 11830–11837. doi:10.1021/jf801521e Muttucumaru, N., Elmore, J.S., Curtis, T., Mottram, D.S., Parry, M.A.J., Halford, N.G., 2008. Reducing acrylamide precursors in raw materials derived from wheat and potato. J. Agric. Food Chem. 56, 6167–6172. doi:10.1021/jf800279d Nardini, M., Cirillo, E., Natella, F., Mencarelli, D., Comisso, A., Scaccini, C., 2002. Detection of bound phenolic acids: prevention by ascorbic acid and ethylenediaminetetraacetic acid of degradation of phenolic acids during alkaline hydrolysis. Food Chem. 79, 119–124. doi:10.1016/S0308-8146(02)00213-3 Narita, Y., Inouye, K., 2013. Degradation Kinetics of Chlorogenic Acid at Various pH Values and Effects of Ascorbic Acid and Epigallocatechin Gallate on Its Stability under Alkaline Conditions. J. Agric. Food Chem. 61, 966–972. doi:10.1021/jf304105w Navarre, D.A., Goyer, A., Shakya, R., 2009. Chapter 14 - Nutritional Value of Potatoes: Vitamin, Phytonutrient, and Mineral Content, in: Singh, J., Kaur, L. (Eds.), Advances in Potato Chemistry and Technology. Academic Press, San Diego, pp. 395–424. Navarre, D.A., Payyavula, R.S., Shakya, R., Knowles, N.R., Pillai, S.S., 2013. Changes in potato phenylpropanoid metabolism during tuber development. Plant Physiol. Biochem. 65, 89–101. doi:10.1016/j.plaphy.2013.01.007 Navarre, D.A., Pillai, S.S., Shakya, R., Holden, M.J., 2011. HPLC profiling of phenolics in diverse potato genotypes. Food Chem. 127, 34–41. doi:10.1016/j.foodchem.2010.12.080

107

108

Navarre, D.A., Shakya, R., Holden, J., Kumar, S., 2010. The Effect of Different Cooking Methods on Phenolics and Vitamin C in Developmentally Young Potato Tubers. Am. J. Potato Res. 87, 350–359. doi:10.1007/s12230-010-9141-8 Nayak, B., De J. Berrios, J., Tang, J., 2014. Impact of food processing on the glycemic index (GI) of potato products. Food Res. Int. 56, 35–46. doi:10.1016/j.foodres.2013.12.020 Neilson, A.P., Ferruzzi, M.G., 2011. Influence of formulation and processing on absorption and metabolism of flavan-3-ols from tea and cocoa. Annu. Rev. Food Sci. Technol. 2, 125–151. doi:10.1146/annurev-food-022510-133725 Neilson, A.P., Sapper, T.N., Janle, E.M., Rudolph, R., Matusheski, N.V., Ferruzzi, M.G., 2010. Chocolate matrix factors modulate the pharmacokinetic behavior of cocoa flavan-3- ol phase II metabolites following oral consumption by Sprague-Dawley rats. J. Agric. Food Chem. 58, 6685–6691. doi:10.1021/jf1005353 New World Catalogue of Potato Varieties [WWW Document], 2009. . Int. Potato Cent. URL http://cipotato.org/press-room/press-releases/new-world-catalogue-of-potato- varieties/ (accessed 11.20.14). Niwano, Y., Adachi, T., Kashimura, J., Sakata, T., Sasaki, H., Sekine, K., Yamamoto, S., Yonekubo, A., Kimura, S., 2009. Is glycemic index of food a feasible predictor of appetite, hunger, and satiety? J. Nutr. Sci. Vitaminol. (Tokyo) 55, 201–207. Noda, T., Takigawa, S., Matsuura-Endo, C., Suzuki, T., Hashimoto, N., Kottearachchi, N.S., Yamauchi, H., Zaidul, I.S.M., 2008. Factors affecting the digestibility of raw and gelatinized potato starches. Food Chem. 110, 465–470. doi:10.1016/j.foodchem.2008.02.027 Nugent, A.P., 2005. Health properties of resistant starch. Nutr. Bull. 30, 27–54. doi:10.1111/j.1467-3010.2005.00481.x Oakes, M.E., 2004. Good foods gone bad: “infamous” nutrients diminish perceived vitamin and mineral content of foods. Appetite 42, 273–278. doi:10.1016/j.appet.2003.10.004 O’Connor, C. j., Fisk, K. j., Smith, B. g., Melton, L. d., 2001. Fat Uptake in French Fries as Affected by Different Potato Varieties and Processing. J. Food Sci. 66, 903–908. doi:10.1111/j.1365-2621.2001.tb15194.x Oki, T., Masuda, M., Furuta, S., Nishiba, Y., Terahara, N., Suda, I., 2002. Involvement of Anthocyanins and other Phenolic Compounds in Radical-Scavenging Activity of Purple-Fleshed Sweet Potato Cultivars. J. Food Sci. 67, 1752–1756. doi:10.1111/j.1365-2621.2002.tb08718.x Oki, T., Suda, I., Terahara, N., Sato, M., Hatakeyama, M., 2006. Determination of Acylated Anthocyanin in Human Urine after Ingesting a Purple-Fleshed Sweet Potato Beverage with Various Contents of Anthocyanin by LC-ESI-MS/MS. Biosci. Biotechnol. Biochem. 70, 2540–2543. doi:10.1271/bbb.60187 Olthof, M.R., Hollman, P.C.H., Katan, M.B., 2001. Chlorogenic Acid and Caffeic Acid Are Absorbed in Humans. J. Nutr. 131, 66–71. Papathanasiou, F., Mitchell, S.H., Harvey, B.M.R., 1998. Glycoalkaloid accumulation during tuber development of early potato cultivars. Potato Res. 41, 117–125. doi:10.1007/BF02358434 Patras, A., Brunton, N.P., O’Donnell, C., Tiwari, B.K., 2010. Effect of thermal processing on anthocyanin stability in foods; mechanisms and kinetics of degradation. Trends Food Sci. Technol. 21, 3–11. doi:10.1016/j.tifs.2009.07.004

108

109

Payyavula, R.S., Navarre, D.A., Kuhl, J., Pantoja, A., 2013. Developmental Effects on Phenolic, Flavonol, Anthocyanin, and Carotenoid Metabolites and Gene Expression in Potatoes. J. Agric. Food Chem. 61, 7357–7365. doi:10.1021/jf401522k Payyavula, R.S., Shakya, R., Sengoda, V.G., Munyaneza, J.E., Swamy, P., Navarre, D.A., 2014. Synthesis and regulation of chlorogenic acid in potato: Rerouting phenylpropanoid flux in HQT-silenced lines. Plant Biotechnol. J. doi:10.1111/pbi.12280 Pedreschi, F., Cocio, C., Moyano, P., Troncoso, E., 2008. Oil distribution in potato slices during frying. J. Food Eng. 87, 200–212. doi:10.1016/j.jfoodeng.2007.11.031 Pedreschi, F., Mariotti, M.S., Granby, K., 2014. Current issues in dietary acrylamide: formation, mitigation and risk assessment. J. Sci. Food Agric. 94, 9–20. doi:10.1002/jsfa.6349 Pellegrini, N., Miglio, C., Del Rio, D., Salvatore, S., Serafini, M., Brighenti, F., 2009. Effect of domestic cooking methods on the total antioxidant capacity of vegetables. Int. J. Food Sci. Nutr. 60, 12–22. doi:10.1080/09637480802175212 Peters, C.M., Green, R.J., Janle, E.M., Ferruzzi, M.G., 2010. Formulation with ascorbic acid and sucrose modulates catechin bioavailability from green tea. Food Res. Int. Ott. Ont 43, 95–102. doi:10.1016/j.foodres.2009.08.016 Petersson, E.V., Arif, U., Schulzova, V., Krtková, V., Hajšlová, J., Meijer, J., Andersson, H.C., Jonsson, L., Sitbon, F., 2013. Glycoalkaloid and calystegine levels in table potato cultivars subjected to wounding, light, and heat treatments. J. Agric. Food Chem. 61, 5893–5902. doi:10.1021/jf400318p Pieterse, L., Hils, U., 2009. World catalogue of potato varieties. Agrimedia, Clenze. Raben, A., 2002. Should obese patients be counselled to follow a low-glycaemic index diet? No. Obes. Rev. Off. J. Int. Assoc. Study Obes. 3, 245–256. Raigond, P., Ezekiel, R., Raigond, B., 2014. Resistant starch in food: a review. J. Sci. Food Agric. n/a–n/a. doi:10.1002/jsfa.6966 Ramdath, D.D., Padhi, E., Hawke, A., Sivaramalingam, T., Tsao, R., 2014. The glycemic index of pigmented potatoes is related to their polyphenol content. Food Funct. 5, 909. doi:10.1039/c3fo60395d Reboul, E., Richelle, M., Perrot, E., Desmoulins-Malezet, C., Pirisi, V., Borel, P., 2006. Bioaccessibility of carotenoids and vitamin E from their main dietary sources. J. Agric. Food Chem. 54, 8749–8755. doi:10.1021/jf061818s Reddivari, L., Hale, A.L., Miller, J.C., 2007. Determination of phenolic content, composition and their contribution to antioxidant activity in specialty potato selections. Am. J. Potato Res. 84, 275–282. doi:10.1007/BF02986239 Reyes, L.F., Miller, J.C., Cisneros-Zevallos, L., 2004. Environmental conditions influence the content and yield of anthocyanins and total phenolics in purple- and red-flesh potatoes during tuber development. Am. J. Potato Res. 81, 187–193. doi:10.1007/BF02871748 Robert, L., Narcy, A., Rayssiguier, Y., Mazur, A., Rémésy, C., 2008. Lipid metabolism and antioxidant status in sucrose vs. potato-fed rats. J. Am. Coll. Nutr. 27, 109–116. Robert, L., Narcy, A., Rock, E., Demigne, C., Mazur, A., Rémésy, C., 2006. Entire potato consumption improves lipid metabolism and antioxidant status in cholesterol-fed rat. Eur. J. Nutr. 45, 267–274. doi:10.1007/s00394-006-0594-y Rodriguez De Sotillo, D., Hadley, M., Holm, E.T., 1994. Potato Peel Waste: Stability and Antioxidant Activity of a Freeze-Dried Extract. J. Food Sci. 59, 1031–1033. doi:10.1111/j.1365-2621.1994.tb08182.x

109

110

Rodriguez-Saona, L.E., Giusti, M.M., Wrolstad, R.E., 1998. Anthocyanin Pigment Composition of Red-fleshed Potatoes. J. Food Sci. 63, 458–465. doi:10.1111/j.1365- 2621.1998.tb15764.x Rommens, C.M., Yan, H., Swords, K., Richael, C., Ye, J., 2008. Low-acrylamide French fries and potato chips. Plant Biotechnol. J. 6, 843–853. doi:10.1111/j.1467- 7652.2008.00363.x Rommens, C.M., Ye, J., Richael, C., Swords, K., 2006. Improving Potato Storage and Processing Characteristics through All-Native DNA Transformation. J. Agric. Food Chem. 54, 9882–9887. doi:10.1021/jf062477l Rossi, M., Alamprese, C., Ratti, S., 2007. Tocopherols and tocotrienols as free radical- scavengers in refined vegetable oils and their stability during deep-fat frying. Food Chem. 102, 812–817. doi:10.1016/j.foodchem.2006.06.016 Rothwell, J.A., Perez-Jimenez, J., Neveu, V., Medina-Remón, A., M’Hiri, N., García-Lobato, P., Manach, C., Knox, C., Eisner, R., Wishart, D.S., Scalbert, A., 2013. Phenol-Explorer 3.0: a major update of the Phenol-Explorer database to incorporate data on the effects of food processing on polyphenol content. Database 2013, bat070. doi:10.1093/database/bat070 Ruiz, G.M., Polvillo, M.M., Jorge, N., Méndez, M.V.R., Dobarganes, M.C., 1999. Influence of used frying oil quality and natural tocopherol content on oxidative stability of fried potatoes. J. Am. Oil Chem. Soc. 76, 421–425. doi:10.1007/s11746-999-0019-1 Rusinovci, I., Aliu, S., Fetahu, S., Kaçiu, S., Salihu, S., Zeka, D., Berisha, D., 2012. Contents of mineral substances in the potato (Solanum tuberosum L.) tubers depending on cultivar and locality in the agro-ecological conditions of Kosovo, Acta Horticulturae. Ryan, G.B., Majno, G., 1977. Acute inflammation. A review. Am. J. Pathol. 86, 183–276. Sadilova, E., Stintzing, F.C., Carle, R., 2006. Thermal Degradation of Acylated and Nonacylated Anthocyanins. J. Food Sci. 71, C504–C512. doi:10.1111/j.1750- 3841.2006.00148.x Sajilata, M. g., Singhal, R.S., Kulkarni, P.R., 2006. Resistant Starch–A Review. Compr. Rev. Food Sci. Food Saf. 5, 1–17. doi:10.1111/j.1541-4337.2006.tb00076.x Schramm, D.D., Karim, M., Schrader, H.R., Holt, R.R., Kirkpatrick, N.J., Polagruto, J.A., Ensunsa, J.L., Schmitz, H.H., Keen, C.L., 2003. Food effects on the absorption and pharmacokinetics of cocoa flavanols. Life Sci. 73, 857–869. doi:10.1016/S0024- 3205(03)00373-4 Shallenberger, R.S., Smith, O., Treadway, R.H., 1959. Food Color Changes, Role of the Sugars in the Browning Reaction in Potato Chips. J. Agric. Food Chem. 7, 274–277. doi:10.1021/jf60098a010 Shikany, J.M., White Jr., G.L., 2000. Dietary Guidelines for Chronic Disease Prevention. South. Med. J. 93, 1138. Singh, J., Kaur, L., McCarthy, O.J., 2009. Chapter 10 - Potato Starch and its Modification, in: Singh, J., Kaur, L. (Eds.), Advances in Potato Chemistry and Technology. Academic Press, San Diego, pp. 273–318. Slavin, J.L., 2013. Carbohydrates, Dietary Fiber, and Resistant Starch in White Vegetables: Links to Health Outcomes. Adv. Nutr. Int. Rev. J. 4, 351S–355S. doi:10.3945/an.112.003491 Soh, N., Brand-Miller, J., 1999. The glycaemic index of potatoes: the effect of variety, cooking method, and maturity. Eur. J. Clin. Nutr. 53, 249–254.

110

111

Song, B.J., Sapper, T.N., Burtch, C.E., Brimmer, K., Goldschmidt, M., Ferruzzi, M.G., 2013. Photo- and Thermodegradation of Anthocyanins from Grape and Purple Sweet Potato in Model Beverage Systems. J. Agric. Food Chem. 61, 1364–1372. doi:10.1021/jf3044007 Sowokinos, J.R., 2001. Biochemical and molecular control of cold-induced sweetening in potatoes. Am. J. Potato Res. 78, 221–236. doi:10.1007/BF02883548 Spychalla, J.P., Desborough, S.L., 1990. Superoxide Dismutase, Catalase, and α-Tocopherol Content of Stored Potato Tubers. Plant Physiol. 94, 1214–1218. doi:10.1104/pp.94.3.1214 Stalmach, A., Williamson, G., Crozier, A., 2014. Impact of dose on the bioavailability of coffee chlorogenic acids in humans. Food Funct. 5, 1727–1737. doi:10.1039/c4fo00316k Stöckigt, J., Zenk, M.H., 1974. Enzymatic synthesis of chlorogenic acid from caffeoyl coenzyme A and quinic acid. FEBS Lett. 42, 131–134. doi:10.1016/0014- 5793(74)80769-6 Storey, M., 2007. Chapter 21 - The harvested crop, in: Bradshaw, D.V., Gebhardt, C., Govers, F., Mackerron, D.K.L., Taylor, M.A., Ross, H.A. (Eds.), Potato Biology and Biotechnology. Elsevier Science B.V., Amsterdam, pp. 441–470. Storey, M.L., Anderson, P.A., 2013. Contributions of White Vegetables to Nutrient Intake: NHANES 2009–2010. Adv. Nutr. Int. Rev. J. 4, 335S–344S. doi:10.3945/an.112.003541 Stubenitsky, K., Mela, D.J., 2000. UK consumer perceptions of starchy foods. Br. J. Nutr. 83, 277–285. doi:10.1017/S0007114500000350 Suda, I., Oki, T., Masuda, M., Nishiba, Y., Furuta, S., Matsugano, K., Sugita, K., Terahara, N., 2002. Direct Absorption of Acylated Anthocyanin in Purple-Fleshed Sweet Potato into Rats. J. Agric. Food Chem. 50, 1672–1676. doi:10.1021/jf011162x Tahvonen, R., Hietanen, R.M., Sihvonen, J., Salminen, E., 2006. Influence of different processing methods on the glycemic index of potato (Nicola). J. Food Compos. Anal., After Processing: The Fate of Food Components 19, 372–378. doi:10.1016/j.jfca.2005.10.008 Takahata, Y., Noda, T., Nagata, T., 1993. HPLC Determination of β-Carotene Content of Sweet Potato Cultivars and Its Relationship with Color Values. Jpn. J. Breed. 43, 421–427. doi:10.1270/jsbbs1951.43.421 Takenaka, M., Nanayama, K., Isobe, S., Murata, M., 2006. Changes in Caffeic Acid Derivatives in Sweet Potato (Ipomoea batatas L.) during Cooking and Processing. Biosci. Biotechnol. Biochem. 70, 172–177. doi:10.1271/bbb.70.172 Tarazona-Díaz, M.P., Aguayo, E., 2013. Assessment of by-products from fresh-cut products for reuse as bioactive compounds. Food Sci. Technol. Int. Cienc. Tecnol. Los Aliment. Int. 19, 439–446. doi:10.1177/1082013212455346 Tareke, E., Rydberg, P., Karlsson, P., Eriksson, S., Törnqvist, M., 2000. Acrylamide: a cooking carcinogen? Chem. Res. Toxicol. 13, 517–522. Teow, C.C., Truong, V.-D., McFeeters, R.F., Thompson, R.L., Pecota, K.V., Yencho, G.C., 2007. Antioxidant activities, phenolic and β-carotene contents of sweet potato genotypes with varying flesh colours. Food Chem. 103, 829–838. doi:10.1016/j.foodchem.2006.09.033 Thed, S.T., Phillips, R.D., 1995. Changes of dietary fiber and starch composition of processed potato products during domestic cooking. Food Chem. 52, 301–304. doi:10.1016/0308-8146(95)92828-8

111

112

Thompson, L.U., Yoon, J.H., Jenkins, D.J., Wolever, T.M., Jenkins, A.L., 1984. Relationship between polyphenol intake and blood glucose response of normal and diabetic individuals. Am. J. Clin. Nutr. 39, 745–751. Thornton, R.E., Sieczka, J.B., 1980. Commercial potato production in North America. Am. Potato J. 57. Toma, R.B., Orr, P.H., D’appolonia, B., DlNTZIS, F.R., Tabekhia, M.M., 1979. Physical and Chemical Properties of Potato Peel as a Source of Dietary Fiber in Bread. J. Food Sci. 44, 1403–1407. doi:10.1111/j.1365-2621.1979.tb06448.x True, R.H., Hogan, J.M., Augustin, J., Johnson, S.R., Teitzel, C., Toma, R.B., Orr, P., 1979. Changes in the nutrient composition of potatoes during home preparation: III. Minerals. Am. Potato J. 56, 339–350. doi:10.1007/BF02853849 Tudela, J.A., Cantos, E., Espín, J.C., Tomás-Barberán, F.A., Gil, M.I., 2002. Induction of Antioxidant Flavonol Biosynthesis in Fresh-Cut Potatoes. Effect of Domestic Cooking. J. Agric. Food Chem. 50, 5925–5931. doi:10.1021/jf020330y Tudela, J.A., Espı́n, J.C., Gil, M.I., 2002. Vitamin C retention in fresh-cut potatoes. Postharvest Biol. Technol. 26, 75–84. doi:10.1016/S0925-5214(02)00002-9 United States Department of Agriculture, 2015. What counts as a cup of vegetables? [WWW Document]. choosemyplate.gov. URL http://www.choosemyplate.gov/food- groups/vegetables-counts.html (accessed 4.2.15). United States Potato Board, 2007a. Chip Stock Potatoes [WWW Document]. URL http://www.potatoesusa.com/products.php?sec=Chip-Stock%20Potatoes (accessed 12.17.14). United States Potato Board, 2007b. Table-Stock Potatoes [WWW Document]. URL http://www.potatoesusa.com/products.php?sec=Chip-Stock%20Potatoes (accessed 12.17.14). USDA Economic Research Service, 2014. USDA Economic Research Service - Potatoes [WWW Document]. URL http://www.ers.usda.gov/topics/crops/vegetables- pulses/potatoes.aspx (accessed 11.6.14). US Department of Agriculture Agricultural Research Service, 2014. USDA National Nutrient Database for Standard Reference Release. United States Department of Agriculture: Agricultural Research Service. U.S. Food and Drug Administration, 2015. Biotechnology Consultation Note to the File BNF No. 000141: Genetically Engineered Potato Varieties (No. 000141). U.S. Food and Drug Administration. Van Dam, R.M., Hu, F.B., 2005. Coffee consumption and risk of type 2 diabetes: a systematic review. JAMA 294, 97–104. doi:10.1001/jama.294.1.97 Van Jaarsveld, P.J., Marais, D.W., Harmse, E., Nestel, P., Rodriguez-Amaya, D.B., 2006. Retention of β-carotene in boiled, mashed orange-fleshed sweet potato. J. Food Compos. Anal., After Processing: The Fate of Food Components 19, 321–329. doi:10.1016/j.jfca.2004.10.007 Vaziri, N.D., Liu, S.-M., Lau, W.L., Khazaeli, M., Nazertehrani, S., Farzaneh, S.H., Kieffer, D.A., Adams, S.H., Martin, R.J., 2014. High amylose resistant starch diet ameliorates oxidative stress, inflammation, and progression of chronic kidney disease. PloS One 9, e114881. doi:10.1371/journal.pone.0114881 Vinha, A.F., Alves, R.C., Barreira, S.V.P., Costa, A.S.G., Oliveira, M.B.P.P., 2015. Impact of boiling on phytochemicals and antioxidant activity of green vegetables consumed in the Mediterranean diet. Food Funct. 6, 1157–1163. doi:10.1039/c4fo01209g

112

113

Vitaglione, P., Mennella, I., Ferracane, R., Rivellese, A.A., Giacco, R., Ercolini, D., Gibbons, S.M., La Storia, A., Gilbert, J.A., Jonnalagadda, S., Thielecke, F., Gallo, M.A., Scalfi, L., Fogliano, V., 2015. Whole-grain wheat consumption reduces inflammation in a randomized controlled trial on overweight and obese subjects with unhealthy dietary and lifestyle behaviors: role of polyphenols bound to cereal dietary fiber. Am. J. Clin. Nutr. 101, 251–261. doi:10.3945/ajcn.114.088120 Volden, J., Borge, G.I.A., Bengtsson, G.B., Hansen, M., Thygesen, I.E., Wicklund, T., 2008. Effect of thermal treatment on glucosinolates and antioxidant-related parameters in red cabbage (Brassica oleracea L. ssp. capitata f. rubra). Food Chem. 109, 595–605. doi:10.1016/j.foodchem.2008.01.010 Vreugdenhil, D., Bradshaw, J., Gebhardt, C., Govers, F., Taylor, M.A., MacKerron, D.K.L., Ross, H.A., 2011. Potato Biology and Biotechnology: Advances and Perspectives: Advances and Perspectives. Elsevier. Wang, D., Williams, B.A., Ferruzzi, M.G., D’Arcy, B.R., 2013. Different concentrations of grape seed extract affect in vitro starch fermentation by porcine small and large intestinal inocula. J. Sci. Food Agric. 93, 276–283. doi:10.1002/jsfa.5753 Watada, A.E., Kunkel, R., 1955. The variation in reducing sugar content in different varieties of potatoes. Am. Potato J. 32, 132–140. doi:10.1007/BF02851208 Watanabe, K., 2015. Potato genetics, genomics, and applications. Breed. Sci. 65, 53–68. doi:10.1270/jsbbs.65.53 Wells, H.F., Thornsbury, S., Bond, J., 2013. Vegetables and Pulses Outlook (No. VGS-353). United States Department of Agriculture: Economic Research Service. White, P.J., Bradshaw, J.E., Finlay, M., Dale, B., Ramsay, G., Hammond, J.P., Broadley, M.R., 2009. Relationships Between Yield and Mineral Concentrations in Potato Tubers. HortScience 44, 6–11. Wilson, A.M., Work, T.M., Bushway, A.A., Bushway, R.J., 1981. HPLC Determination of Fructose, Glucose, and Sucrose in Potatoes. J. Food Sci. 46, 300–301. doi:10.1111/j.1365-2621.1981.tb14589.x Wszelaki, A.L., Delwiche, J.F., Walker, S.D., Liggett, R.E., Scheerens, J.C., Kleinhenz, M.D., 2005. Sensory quality and mineral and glycoalkaloid concentrations in organically and conventionally grown redskin potatoes (Solanum tuberosum). J. Sci. Food Agric. 85, 720–726. doi:10.1002/jsfa.2051 Xu, X., Li, W., Lu, Z., Beta, T., Hydamaka, A.W., 2009. Phenolic Content, Composition, Antioxidant Activity, and Their Changes during Domestic Cooking of Potatoes. J. Agric. Food Chem. 57, 10231–10238. doi:10.1021/jf902532q Zafra-Stone, S., Yasmin, T., Bagchi, M., Chatterjee, A., Vinson, J.A., Bagchi, D., 2007. Berry anthocyanins as novel antioxidants in human health and disease prevention. Mol. Nutr. Food Res. 51, 675–683. doi:10.1002/mnfr.200700002 Zaheer, K., Akhtar, M.H., 2014. Recent advances in potato production, usage, nutrition-a Review. Crit. Rev. Food Sci. Nutr. doi:10.1080/10408398.2012.724479 Zhang, Y., Zhang, Y., 2007. Formation and Reduction of Acrylamide in Maillard Reaction: A Review Based on the Current State of Knowledge. Crit. Rev. Food Sci. Nutr. 47, 521– 542. doi:10.1080/10408390600920070 Zhu, F., Cai, Y.-Z., Ke, J., Corke, H., 2010. Compositions of phenolic compounds, amino acids and reducing sugars in commercial potato varieties and their effects on acrylamide formation. J. Sci. Food Agric. 90, 2254–2262. doi:10.1002/jsfa.4079

113

114

Ziaiifar, A.M., Achir, N., Courtois, F., Trezzani, I., Trystram, G., 2008. Review of mechanisms, conditions, and factors involved in the oil uptake phenomenon during the deep-fat frying process. Int. J. Food Sci. Technol. 43, 1410–1423. doi:10.1111/j.1365- 2621.2007.01664.x

114

APPENDICES 115

Appendix A: Other phytochemicals detected but not quantified in potatoes

m/z Compound Associated Varieties Detected In 137 Salicylic acid - 153 Protocatechuic acid - 163 p-Coumaric acid Bintje, ADB, AR2009-10 167 Vanillic acid Innovator 169 Gallic acid ADB, AR2009-10, Bintje, Innvoator, Norland, Yukon 193 Ferulic acid ADB, ADR, Bintje, Innovator, Norland, Yukon 197 Syringic acid - 223 Synapic acid ADR, Norland 285 Kaempferol ADB, ADR 289 Catechin - 301 Quercetin - 593 Kaempferol-3-rutinoside ADB, ADR, AR2009-10 609 Rutin (quercetin-3-O-rutinoside) AR2009-10, ADR, Bintje, Yukon

115

116

Appendix B: Chlorogenic acid content in raw Covington potatoes destined for sweet potato fries and wedges

mg 5-CQA/100 g dw Covington for Fry F 68.1 ± 1.5 W 75.1 ± 25 Covington for Wedge F 132.9 ± 8.7 W 222.8 ± 26

116

Appendix C: Nutritional data and % moisture for raw potato varieties1

Total Carb. Fiber Sugars Protein Vitamin Vitamin Iron Calcium Magnesium Potassium Zinc % Variety Part Calories (g) (g) (g) (g) A (IU) C (mg) (mg) (mg) (mg) (mg) (mg) Moisture R. Burbank Peel 86.0 19.0 3.93 0.36 2.50 <5 8.74 33.2 20.1 31.9 437 0.48 76.7 ADB Peel 72.7 16.0 3.33 0.72 2.18 14 15.3 25.0 13.8 27.9 372 0.35 80.3 ADR Peel 65.4 14.0 4.28 0.71 2.34 <5 6.75 23.4 18.5 27.9 315 0.37 82.4 AR2009-10 Peel 68.8 14.9 3.54 0.33 2.30 <5 8.55 23.8 16.4 35.1 418 0.41 81.2 Bintje Peel 75.4 17.0 2.90 0.58 1.84 <5 8.19 18.9 23.0 28.0 395 0.38 79.8 Yukon Peel 71.5 15.4 3.10 <0.25 2.24 <5 10.0 18.8 16.4 32.8 486 0.28 80.7 Challenger Peel 70.9 15.8 5.52 <0.25 1.93 <5 12.8 18.0 14.2 29.7 408 0.34 80.9 Innovator Peel 76.6 16.8 5.71 <0.25 2.36 <5 15.0 32.5 21.8 32.7 260 0.39 79.3 Norland Peel 59.1 12.1 3.10 1.31 2.68 24 2.23 58.4 13.8 47.4 466 0.58 82.4

R. Burbank Flesh 90.6 20.9 1.13 1.03 1.74 <5 11.1 1.0 6.5 22.7 252 0.28 76.6 ADB Flesh 64.4 14.3 1.28 0.89 1.79 <5 16.4 1.2 3.2 21.4 175 0.30 83.3 ADR Flesh 76.2 17.4 1.59 0.66 1.64 <5 8.71 0.9 5.2 21.9 254 0.26 80.4 AR2009-10 Flesh 77.4 17.3 1.55 0.40 2.05 <5 10.5 1.2 4.6 28.2 310 0.33 79.8 Bintje Flesh 85.5 19.7 1.18 0.40 1.67 <5 13.6 1.3 25.0 23.4 299 0.35 77.9 Yukon Flesh 91.7 20.8 1.74 0.59 2.12 <5 14.4 1.2 4.4 25.6 308 0.24 76.4 Challenger Flesh 83.2 19.2 1.53 <0.25 1.61 <5 15.6 1.1 5.3 23.8 297 0.27 78.3 Innovator Flesh 95.1 21.8 2.52 0.28 1.97 <5 13.5 1.5 7.0 25.1 234 0.35 75.5 Norland Flesh 82.0 15.2 1.14 2.38 2.12 <5 5.75 2.2 2.2 22.0 265 0.30 82.0

1All data per 100 g of raw flesh or peel

117

Appendix D: Nutritional data for commercial and fresh processed potato products1

Poly & Total Sat. Sample Fiber Mono Trans Vit B6 Vit C Iron Sodium Magnesium Potassium Zinc Description Fat Fat Code (g) Unsat Fat Fat (g) (mg) (mg) (mg) (mg) (mg) (mg) (mg) (g) (g) (g) MCFBK McCain, Classic Fry, Baked 5.1 10.2 1.5 8.2 0.08 0.56 10.8 1.7 969 54.7 878 0.91 MCFFD McCain, Classic Fry, Fried 4.7 19.1 1.9 16.4 0.05 0.54 10.4 1.5 922 54.2 771 0.84 PCFBK Purdue, Classic Fry, Baked 5.9 7.1 0.6 6.2 0.02 0.92 19.2 1.6 351 64.9 1250 1.5 PCFFD Purdue, Classic Fry, Fried 5.3 16.1 1.5 13.9 0.04 0.78 11.2 1.7 254 63.7 934 1.3 MHBBK McCain, Hash Browns, Baked 5.7 22.0 1.6 19.4 0.03 0.55 12.3 1.6 66.0 69.9 1130 1.2 MHBPF McCain, Hash Browns, PanFried 6.1 17.7 1.4 15.5 0.03 0.65 9.4 3.2 71.2 68.1 1130 1.2 PHBBK Purdue, Hash Browns, Baked 4.9 13.5 1.0 11.8 0.02 0.66 11.5 1.5 357 75.4 1530 1.3 PHBPF Purdue, Hash Browns, Panfried 4.7 20.6 1.5 18.2 0.03 0.66 11.6 1.5 149 41.3 505 1.2 MSFBK McCain, Sweet Pot. Fry, Baked 7.0 14.0 2.2 11.1 0.07 0.33 15.1 2.2 805 54.4 656 0.76 MSFFD McCain, Sweet Pot. Fry, Fried 9.1 22.0 2.3 18.7 0.06 0.30 11.5 2.1 622 55.1 644 0.72 PSFBK Purdue, Sweet Pot. Fry, Baked 8.4 11.3 1.0 9.8 0.02 0.43 31.7 2.8 338 56.4 973 0.82 PSFFD Purdue, Sweet Pot. Fry, Fried 7.5 16.0 1.6 13.7 0.03 0.34 31.7 2.1 228 52.9 1080 0.80 MSWBK McCain, Swt Pot. Wedge, Baked 13.5 17.9 2.8 14.2 0.08 0.42 23.2 3.5 206 78.2 918 1.1 MSWFD McCain, Swt Pot. Wedge, Fried 7.4 26.4 2.9 22.3 0.07 0.40 23.1 2.4 210 77.6 843 1.0 PSWBK Purdue, Swt Pot. Wedge, Baked 13.4 7.3 0.8 6.2 0.01 0.65 32.0 2.5 334 98.9 1630 0.85 PSWFD Purdue, Swt Pot. Wedge, Fried 10.9 15.7 1.6 13.4 0.04 0.74 23.6 1.5 165 82.9 1390 0.92 MFFFD McCain, Fresh Style Fry, Fried 2.7 25.3 2.3 21.8 0.05 0.35 4.5 0.88 287 30.2 464 0.42 PFFFD Purdue, Fresh Style Fry, Fried 2.8 9.3 0.88 7.98 0.03 0.45 2.7 1.3 196 46.2 804 0.72

1All data per 100 g potato product

118

119

Appendix E: PDCAAS data for raw varieties

Potato Variety PDCAAS (Flesh, without skin) Russet Burbank 51% Innovator 67% Bintje 53% Challenger 71% Yukon Gold 60% Norland Red 60% AR2009-10 43% Adirondack Blue 50% Adirondack Red 39%

119