Storage Conditions, Fatty Acid Composition, and Roasting Methods)

FLAVOR FORMATION AND SENSORY PERCEPTION OF SELECTED PEANUT GENOTYPES (ARACHIS HYPOGEA L.) AS AFFECTED BY STORAGE WATER ACTIVITY, ROASTING, AND PLANTING DATE

GEORGE L. BAKER IV

A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY

UNIVERSITY OF FLORIDA

2002

ACKNOWLEDGMENTS

I would like to thank all of my family, friends, and faculty at the University of

Florida for the care and guidance that they have given me through the past few years.

Thanks go to my committee members (Dr. Robert Bates, Dr. Daniel Gorbet, and Dr.

Steven Talcott) for their outstanding ideas, personal and financial cooperation, as well as those who helped at the Marianna Research Station with the growing, grading and shelling of the peanuts used in these studies. Many thanks go to John Cornell for the suggestions, explanations, and analysis of statistical methods throughout my studies. My appreciation goes to Timothy Sanders et al. and members of the North Carolina State

Food Science Department for roasting the peanuts discussed in the first chapter of this dissertation. I would like to especially thank Dr. Sean F. O’Keefe and Dr. Charles A.

Sims, for their mentorship, financial assistance, and friendship. Last, but definitely not least, I would like to thank my wonderful wife, Florian, for the love, patience, and direction that only she could give.

TABLE OF CONTENTS

Page ACKNOWLEDGEMENTS…………………………...……………………….………….ii

LIST OF TABLES……………………………………………………………………..…vi

LIST OF FIGURES………..…………………………………………………………....viii

ABSTRACT……………………………………………………………………………...xi

CHAPTER

1 INTRODUCTION…….……..……..………………………………………………....1

2 REVIEW OF LITERATURE.………..……..……………………………………..….5

Overview…………………………………………………………………………...…5 History……………………………………………………………………………..…7 Peanut Growth……………………………………………………………….…….…7 Harvesting, Drying, and Storage………………………………………………..…….8 Nutrition…………………………..…………………………………………………..9 Peanut Storage, Stability, and Oxidation……….……...……..………..…………….11 Sensory……………………………………………….……………………..……….14 History and Uses……………………………………………….……………...14 Testing………………………………………………………………….……...15 Peanut Flavor………………………………………………………………….17 Planting Date and Peanut Maturity..…………………..……………………..……....18 Moisture…………………………………………………………..………………….20 Color Development………………………………………………………………...... 21 Applications………………………………………………………..……….....21 Theory………………………………………………………………………....22 Water Activity………………………………………………………..………………23 Formation of Peanut Flavor ……………………………………………….…....…...24 Peanut Roasting…………………………………………………………..…...24 Pyrazine Development……………………………………………………...…25 Solid Phase Microextraction (SPME)………………………………………………..29

iii

3 STORAGE WATER ACTIVITY EFFECTS, OXIDATION AND SENSORY PROPERTIES OF HIGH-OLEIC PEANUTS…………………...……….…..33

Introduction…………………………………………………………………………..33 Materials and Methods…………………………………………………………….…34 Sample Preparation and Storage………………………………………………34 Lipid Extraction and Peroxide Value Determinations………………………...35 Sensory Analysis………………………………………………………..…….35 Statistics……………………………………………………………………….36 Moisture……………………………………………………………………….36 Sorption Isotherms……………………………………………………….……36 Results and Discussion………………………………………………………………36 Moisture……………………………………………………………………….36 Peroxide Values (PVs)………………………………………………………...37 Sensory Analysis………………………………………………………………37 Conclusions…………………………………………………………………….…….39

4 DETERMINATION OF PYRAZINES AND FLAVOR CHANGES IN PEANUTS DURING ROASTING…………………………..………………………46

Introduction…………………………………………………………………………..46 Materials and Methods……………………………………………………………….48 Sample Preparation and Storage…………………………………………….…48 Peanut Roasting..………………………………………………………………49 Sensory Analysis..……………………………………………………………..49 Roast Color……………………………………………….……………………51 Moisture……………………………………………………………………….51 Solid Phase Microextraction (SPME)…………………………………………51 External Standard Preparation………………………………………….51 Sample Preparation……………………………………………………..54 Results and Discussion………………………………………………………………55 Conclusions…………………………………………………………….…………….63

5 FATTY ACID CONTENT, MOISTURE, AND SENSORY EVALUATION OF STORED ROASTED PEANUT GENOTYPES FROM VARIOUS PLANTING DATES…………………………….…………………………………………………93

Introduction…………………………………………………………………………..93 Materials and Methods………………………………………………………………95 Sample Preparation and Storage………………………………………………95 Sensory Analysis………………………………………...……………………96 Moisture.....……………………………………………………………..……..97 Roast Color...……………………………………………………………….....98 Fatty Acids…………………………………………………………………….98 Statistics……………………………………………………………………….99 Results and Discussion………………………………………………………………99

Sensory Analysis………………………………………………………………99 Multiple Planting Date Genotypes (Main Effects)………………………….99 Single Planting Date Genotypes (Main Effects)………..………..……….101 Moisture………………………………………………………………………102 Fatty Acid Analysis…………………………………………………………..102 Conclusions………………………………………………………………………….104

SUMMARY AND CONCLUSIONS…..……………………………….……………116

APPENDIX

A TASTE PANEL SHEETS FOR CHAPTER 2………………..……..………….…118

B TASTE PANEL SHEETS FOR CHAPTER 3………..…………………………...121

C TASTE PANEL SHEETS FOR CHAPTER 4……..……………………………...122

REFERENCES…………………………………..……………………………….…….123

BIOGRAPHICAL SKETCH…………………………………………………………..130

LIST OF TABLES

Table Page

2-1 Fat Comparison of Peanuts to Other Food Products………………………………....9

2-2 Vitamins and Minerals Present in Peanuts and Their Uses in the Body…………….10

2-3 Pyrazine Compounds Found in Peanuts…………………………………………….26

2-4 Odor Thresholds and Odor Descriptors of Selected Pyrazines (ppb) in Water……..26

3-1 Statistics for Sensory Parameters…………………………………………….……..45

3-2 Duncan’s Mean Separation for Sensory Ratings and Storage Water Activity……...45

3-3 Duncan’s Mean Separation for Sensory Ratings During Storage.………………….45

4-1 Balanced Incomplete Block Design for Panelist Presentation……………………...51

4-2 Selected Primary Pyrazine Concentration for Standard Curve…………………..…52

4-3 Linear Regression Equations and R2 values for External Pyrazine Standard………52

4-4 Main Effects of Roasting Treatments (Averaged Across All Genotypes) on Sensory Attributes……………………………………………………………….…72

4-5 Effects of Roasting Time and Temperature on the Sensory Attributes of Peanut Genotypes………………………………………………………..…………………..73

4-6 Effects of Roasting Time and Temperature for Pyrazines, L-value, and Moisture…74

4-7 Statistical Correlations Between Pyrazines, L-value, and Roasted Aroma for Florunner……………………………………………………..………………….…87

4-8 Statistical Correlations Between Pyrazines, L-value, and Roasted Aroma for Florida MDR 98……………………………………………………………………88

4-9 Statistical Correlations Between Pyrazines, L-value, and Roasted Aroma for Georgia Greene……………………………………………………………...……..89

4-10 Statistical Correlations Between Pyrazines, L-value, and Roasted Aroma for SunOleic 97R…………………………………………………….……...…..90

4-11 Coded and Actual Prediction Equations for 2-Methylpyrazine, 2,5- dimethylpyrazine, Total Pyrazines, L-value, Roasted Aroma and Roasted Flavor for Florunner………………………..…………………………………….91

4-12 Coded and Actual Prediction Equations for 2-Methylpyrazine, 2,5- dimethylpyrazine, Total Pyrazines, L-value, Roasted Aroma and Roasted Flavor for Florida MDR 98...……………………..……………………………….91

4-13 Coded and Actual Prediction Equations for 2-Methylpyrazine, 2,5- dimethylpyrazine, Total Pyrazines, L-value, Roasted Aroma and Roasted Flavor for Georgia Greene…………………..………………………………….….92

4-14 Coded and Actual Prediction Equations for 2-Methylpyrazine, 2,5- dimethylpyrazine, Total Pyrazines, L-value, Roasted Aroma and Roasted Flavor for SunOleic 97R….………………..………………………………………92

5-1 Main Effects of Storage Time, Planting Date and Genotype on Sensory Characteristics…………………………………………………………………….106

5-2 ANOVA Interactions for Multiple Planting Dates at Time 0..……….. ……...…..107

5-3 ANOVA Interactions for Multiple Planting Dates at 3 Months of Storage.………108

5-4 ANOVA Interactions for Multiple Planting Dates at 6 Months of Storage……….109

5-5 Main Effects of Storage Time and Variety on Sensory …………….. ……………110

5-6 ANOVA Interactions for Single Planting Date Genotypes..………………………111

5-7 Fatty Acid Percentage for Various Genotypes of Multiple Planting Dates ………112

5-8 Oleic/Linoleic Acid Ratio, Iodine Value, and Percent Saturation of Multiple Planting Date Genotypes…………………………………………………………..113

5-9 Statistical Significance for Fatty Acids Related to Planting Date, Variety, and Their Interaction……………………………………………………………..114

vii

LIST OF FIGURES

Figure Page

2-1 Summary of Autooxidation in Food Systems………………………………………13

2-2 Water Activity and Rate of Oxidation………………………………………………24

2-3 An Unsubstituted Pyrazine………………………………………………………….25

2-4 Maillard Reaction Pathway…………………………………………………………27

2-5 Proposed Alkylpyrazine Formation by Maillard Reactions………………………...28

2-6 SPME Extraction / Desorption Process…………………………………………….30

3-1 Moisture Changes During Storage at Various Water Activities……………………40

3-2 Peroxide Values During Storage at Various Water Activities……………………...40

3-3 Roast Peanutty Flavor During Storage at Various Water Activities……………….41

3-4 Crunchiness During Storage at Various Water Activities………………………….41

3-5 Cardboardy Flavor During Storage at Various Water Activities…………………..42

3-6 Painty Flavor During Storage at Various Water Activities………………………...42

3-7 Crunchiness and Moisture Content Correlation……………………………………43

3-8 Change in Moisture During Storage at Various Water Activities………………….43

3-9 Moisture Sorption Isotherms for High Oleic Peanuts……………………………....44

4-1 SPME Equilibrium……………………………………………………………….….54

4-2 Pyrazine Levels for Florunner at Various Roast Levels ……………………………65

4-3 Pyrazine Levels for Florida MDR 98 at Various Roast Levels ……...…………….66

viii

4-4 Pyrazine Levels for Georgia Greene at Various Roast Levels …………...………..67

4-5 Pyrazine Levels for SunOleic 97R at Various Roast Levels ……………...……….68

4-6 Total Pyrazines for Genotypes at Various Roast Levels …………………………..69

4-7 Hunter L-values for Genotypes at Various Roast Levels ………………………….70

4-8 Moisture Content for All Genotypes After Roasting ………………………………71

4-9 Least Square Means for Peanut Aroma…………………………………………….75

4-10 Least Square Means for Peanut Flavor...………………………………………...76

4-11 Least Square Means for Sweetness….……………………………………….….77

4-12 Least Square Means for Raw Flavor……………………………………………78

4-13 Least Square Means for Bitter Flavor…………………………………………..79

4-14 Least Square Means for Crunchiness…………………………………………...80

4-15 Linear Effects for Peanut Aroma Attribute When Roasted at 1500C…………..81

4-16 Linear Effects for Peanut Aroma Attribute When Roasted at 1750C…….…….81

4-17 Linear Effects for Peanut Flavor Attribute When Roasted at 1500C…….…….82

4-18 Linear Effects for Peanut Flavor Attribute When Roasted at 1750C…….…….82

4-19 Linear Effects for Sweetness Attribute When Roasted at 1500C………...…….83

4-20 Linear Effects for Sweetness Attribute When Roasted at 1750C………...…….83

4-21 Linear Effects for Raw Attribute When Roasted at 1500C………...……….….84

4-22 Linear Effects for Raw Attribute When Roasted at 1750C………...……….….84

4-23 Linear Effects for Bitter Attribute When Roasted at 1500C………...…..….…..85

4-24 Linear Effects for Bitter Attribute When Roasted at 1750C………...…..……...85

4-25 Linear Effects for Crunchiness Attribute When Roasted at 1500…...…..……..86

4-26 Linear Effects for Crunchiness Attribute When Roasted at 1750…...…..……..86

5-1 Percent Oleic Acid for Peanut Genotypes Separated by Planting Date…………...114

5-2 Oleic/Linoleic Acid Ratio for Peanut Genotypes Separated by Planting Date……115

Abstract of Dissertation Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy

FLAVOR FORMATION AND SENSORY PERCEPTION OF SELECTED PEANUT GENOTYPES (ARACHIS HYPOGEA L.) AS AFFECTED BY STORAGE WATER ACTIVITY, ROASTING, AND PLANTING DATE

George L. Baker IV

May 2002

Chair: Charles A. Sims Major Department: Food Science and Human Nutrition

Peanuts (Arachis hypogea L.) are a major commodity throughout the world and the southeastern U.S. Planting date, maturity at harvest, initial moisture content, storage water activity, peanut variety, and fatty acid composition play a role in roasted peanut flavor and oxidative stability.

Peanut storage conditions have significant effects on overall quality. High-oleic peanuts (peanut seed with 74+% oleic fatty acid oil chemistry) maintain best product quality (low oxidation rate, maintenance of desirable flavor, and crunchiness) when stored at water activities between 0.33 and 0.44. Above this range, crunchiness decreased and oxidation increased, whereas below the range, the oxidation rate increased.

Planting date did not affect peanut flavor, sweetness, painty, or cardboardy sensory scores, with the exception of the 4-15-98 early planting date, which had lower

sensory values. Early May appears to be the best time to plant peanuts as a function of

sensory potential. SunOleic 97R had the highest roasted peanut scores and the lowest

levels of oxidation over six months of storage, among the genotypes evaluated. Roasted

peanut flavor and sweetness declined during storage regardless of variety or planting

date. Fatty acid profile did not significantly change as a function of planting date.

Oleic/linoleic acid ratios increased in late maturity peanuts, thus increasing oxidative

stability.

Peanuts available for commercial roasting tend to be a mixture of genotypes, seed

sizes, maturities, and seed composition. Color measurement is currently used to predict

roasted flavor in peanuts but does not account for genotypes that have the propensity to

roast to a darker color without increased formation of flavor. During peanut roasting,

pyrazines and other flavor compounds are formed via Maillard reactions, and strongly

correlate with roasted flavor and aroma. A rapid method for measuring pyrazine

compounds using headspace solid-phase microextraction (SPME) was developed. This

method was used to analyze peanuts roasted under a variety of time-temperature

combinations. Florida MDR 98 formed the highest levels of pyrazines under the same

roasting conditions, followed by Florunner, Georgia Greene, and SunOleic 97R,

respectively. Of all pyrazines tested, 2,5-dimethylpyrazine most highly correlated to roast peanut flavor and aroma.

Key Words: high-oleic peanut, oxidation, peanuts, planting date, pyrazines, solid-phase microextraction, water activity

xii

CHAPTER 1 INTRODUCTION

Peanuts (Arachis hypogea L.) are a major world oil seed crop. For the past

quarter century, India, China, and the United States have been the major producers of the

peanut (~70% of the world crop). Approximately 23 million tons of peanuts are harvested every year, worldwide, where ~8% comes from the United States (~1.8 million tons/year) (United States Department of Agriculture [USDA], 2001).

Growth parameters before harvesting play a significant part in the overall quality

of peanuts and corresponding flavor potential. The main influence on yield and quality

of peanuts appears to be climate temperature during growth (see subhead Planting Date).

The more favorable the climate is to growth, the more mature a given lot of peanuts will

be. Maturity has a significant effect on flavor potential in peanuts (McNeill and Sanders,

1996; McNeill and Sanders, 1998 a and b, Mozingo et al., 1991; Pattee et al., 1995;

Sanders et al., 1989 a & b; Sanders and Bett, 1995). Harvest and planting date studies

show strong relationships in maturity and overall peanut quality, with no significant

relationship to pod size (McNeill and Sanders, 1996). McNeill and Sanders (1996) noted

that peanuts from mature pods have greater flavor potential than those from immature

pods.

In the U.S., peanuts are normally eaten after some sort of heating. Cooking

methods are rather vast, ranging by method (oven-roasted, microwave-roasted, boiled,

fried, etc.) and time/temperature combinations. For these reasons, there are many ways

1 2

to process peanuts but one primary way to measure roast levels. Currently, the method

for evaluating roasted peanut flavor is based on the roast color via light reflectance (see

Color Development). An L-value is assigned to a sample of roasted peanuts based on the

darkness of roast and this number will dictate the predicted roasted peanut flavor. The

typical L-value for a medium-roast peanut is ~51 (Sanders et al., 1989a). This is a

relatively simple method and is a good indicator of roast flavor. However, there are

differences in roasted peanut flavor and roast color between genotypes of peanuts.

In roasted foods, pyrazines or alkylpyrazines are formed via Maillard reactions

above 700C, and contribute to roasted or cooked flavors (Maga and Sizer, 1973).

Formation of roasted flavor components in peanuts is especially apparent when peanut seeds are heated above 1300C (Landman et al., 1994). Pyrazines play a roll in the flavor

when roasting peanuts, coffee beans, sesame seeds, barley, cocoa, popcorn, potato

products, rye crisp bread and beef. Over 40 pyrazines have been isolated and identified

in peanuts. Measurement of pyrazines may be a better predictor of roasted peanut flavor

and aroma than the current method of color measurement. In order for pyrazine

measurement to be efficient enough to be valuable to peanut processors, the methodology

must be faster than traditional methods of measuring volatile flavor compounds.

Roughly ten years ago, a new invention named solid-phase microextraction (SPME) was

introduced to the scientific community. Solid-phase microextraction and its ability to

quickly extract volatile compounds from a headspace, make rapid compound detection

possible with a gas chromatograph. Solid-phase microextraction could then be used to

measure pyrazine levels in peanuts, allowing for improved prediction of roasted peanut

flavor and aroma when compared to color measurement.

Roasted peanuts have a unique, desirable, flavorful aroma, taste, and texture when

freshly roasted. In general, peanuts and peanut oil (~50% of the peanut) tend to have greater shelf lives when compared to other high oil foods (O’Keefe et al., 1993). The

term shelf life, in regard to peanuts or peanut oil, can be described as “the number of days

before the onset of oxidative rancidity, a process which is generally induced in either the

whole peanut or peanut oil by exposure to heat and air” (Mercer et al., 1990). This

definition implies that the shelf life of peanuts is only as long as the time it takes before

the onset of oxidative rancidity, or “having the unpleasant taste or smell of oily

substances that have begun to spoil” (Funk and Wagnall’s 1997 Standard Desk

Dictionary).

Water activity plays an important role in the oxidation of peanuts. Peanut

processors have reported shelf lives as short as seven weeks in packaged confectionary

products due to oxidative rancidity believed to be caused from peanut oil. Control of

water activity decreases oxidative rancidity in stored peanuts and walnuts (Mate et al.,

1996). Water activity not only plays a role in oxidation but also affects sensory

crispness, crunchiness, and textural changes in snack foods and breakfast cereals, as well

as color and flavor formation under roasting conditions (Katz and Labuza, 1981;

Lingnert, 1990; Sauvageot and Blond and Blond, 1991).

Peanut processors and handlers can use what we know of the relationship to fatty

acid composition, water activity, and the theories of lipid oxidation to increase shelf life

(See Peanut Storage, Stability, and Oxidation). By minimizing the amount of oxygen

contact (possibly by flushing with nitrogen and/or vacuum sealing), the amount of light

exposure (by using brown glass or packaging material with minimal light passage), the

4 amount of heat contact after roasting, the contact to metals such as copper, zinc, or iron, and storage at proper water activities, peanuts can be acceptable for consumption for an increased period of time.

In the vast realm of food science, changes and updates in methodology are ongoing. The following information describes several parameters of importance in peanut processing and storage. Storage condition improvement, variations in planting date and variety, sensory characteristics, and monitoring of flavor development during heating will be explored in detail in regards to peanuts grown in the southeastern U.S.

Sensory acceptance of peanut products, in part, dictates the overall quality. Off flavors formed via autooxidation, under- or over-roasted sensory character, and

“sogginess” in roasted peanuts are unacceptable for commercial sale. Typical methods of sensory science are used in the evaluation of several genotypes of commonly processed and experimental hybrids of runner-type peanuts under a variety of conditions.

Relationships to trapped volatile compounds and sensory attributes are statistically correlated to enhance the measurement of quality in roasted peanuts.

Illustrations of increased shelf life as a function of water activity are indicated by a decrease in lipid oxidation via chemical and psychophysical measurements. Derived conditions for improvement are postulated. Therefore, the overall objective of these studies is to find the optimal conditions for growth, harvest, storage, and roasting of peanut genotypes as a function of sensory quality.

CHAPTER 2 REVIEW OF LITERATURE

Overview

Peanuts (Arachis hypogea L.) continue to be a major commodity throughout the world, with about 23.2 million tons harvested annually. India, China, and the United

States have been the major producers of peanut for the past quarter century, and account for 70% of the world crop (Putnam et al., 1991). The United States produces approximately 1.8 million tons (~8% of the World’s supply) per year in various regions of the country. Georgia is the predominant grower in the U.S., and is projected to produce 667,800 tons in 2001 (USDA National Agricultural Statistics Service, 2001).

Georgia, Virginia, Alabama, North Carolina, Florida, Texas, Oklahoma, and New

Mexico are the major producers of the peanut in the U.S. The commercial peanut crop consists of four predominant market-types:

1. Virginia–sp. Arachis hypogaea L., ssp. hypogaea, produced primarily in Virginia and North Carolina.

2. Spanish–sp. Arachis hypogaea L., ssp. fastigiata, var. vulgaris, produced primarily in Texas and Oklahoma (Southwest).

3. Runner–sp. Arachis hypogaea L., ssp. hypogaea, produced primarily in Georgia, Alabama, and Florida (Southeast).

4. Valencia–sp. Arachis hypogaea L., ssp. fastigiata, var. fastigiata, produced primarily in New Mexico.

Peanuts are a self pollinated plant species, and are not really a seed but a legume that has a symbiotic relationship with Rhizobium bacteria that allow them to fix or

5 6 produce their own nitrogen (Ketring et al., 1982). The two subspecies of peanuts, hypogaea and fastigiata, differ in several ways. The hypogaea subspecies do not flower on the main stem, mature later than fastigiata, require higher amounts of water, produce larger seed than fastigiata, and has alternate branching patterns (alternate pairs of vegetative and reproductive nodes, with no fruiting nodes on the main stem). The fastigiata subspecies, on the other hand, produce flowers on the main stem, mature earlier than hypogaea, require lower amounts of water than hypogaea, produce smaller seed than hypogaea, and has sequential branching patterns (Norden et al., 1982). A. hypogaea fastigiata contain two economically important genotypes, vulgaris (Spanish) and fastigiata (Valencia). Virginia-type peanuts have the largest pods and elongated seeds,

Runner-type peanuts have medium size seed, Spanish-type peanuts have smaller round seeds, and Valencia-type peanuts have an intermediate size and shape.

In comparison to other countries, peanuts are primarily eaten as peanut butter or roasted seed in the U.S. Approximately two-thirds of peanuts grown in the United States are made into peanut butter, candy, confections, salted and shelled peanuts, and in-shell peanuts. The other one-third is pressed for oil, used for animal feed, or seed. “Cocktail” peanuts used for confectionary products are usually Virginia-type, “beer nuts” are usually

Runner-types, “redskin” peanuts are usually Spanish-type, and Valencia and Virginia supply what are usually the “in-shell peanuts” we commonly find at sporting events and roadside stands (Norden et al., 1982). Peanuts used in peanut butter are usually Spanish- type, Runner-type, or a combination of the two, and are based primarily on seed size.

Peanut seeds are used in a variety of products including medicines, soaps, lubricants, and cosmetics. The shells or pods can be used to make fireplace logs, mulch, particleboard,

fertilizer, or animal feed. Vines from the peanut plant are used for ruminant feed, and

provide high protein sources for these animals.

History

Peanut cultivation is believed to have originated in Bolivia and surrounding

countries in South America. Any warm, temperate region of the world has the capability

of growing healthy, edible seeds. North and South American natives grew peanuts for

some time before its written history. The seeds and techniques used by natives were

taken to Europe during early colonization of the United States. During the 16th century,

peanut growth and cultivation techniques quickly spread throughout Africa, Asia, and the

Pacific Islands (Hammons, 1982). Farming communities in the southeastern U.S. used

the peanut plant primarily as a garden crop and was not fully utilized as a food source

until 1870. Peanut’s primary food uses were for hog and cattle pasture and it was not

readily consumed until its commercial unveiling in the 1930’s.

Peanut Growth

Peanut seed germination occurs when the soil temperature reaches 600F and the soil moisture is adequate for the seed to absorb 50% of its weight in water. With adequate moisture, a radical sprouts from the germinating seed a few days after planting. Food reserves are maintained in the cotyledon until the shoots emerge from the soil and begin to accumulate sunlight via photosynthesis (Ketring et al., 1982).

Peanuts are considered to be self-pollinating, with natural cross-pollination rates of less than 1% (Ketring et al., 1982). The fruit of the peanut, is a pod with 1 to 5 seeds that develop underground after the elongated ped with ovarian structure penetrates the soil 3-6 centimeters. Peanut plants produce bright-yellow complete flowers with male

and female parts located in the axils of the leaves. Flowers normally appear 4-6 weeks

after planting and plants continue to flower through the growing season (Ketring et al.,

1982; Sanders et al., 1982). Depending on the variety, peanuts require anywhere from

100 to 150 days from planting to reach full maturity.

Harvesting, Drying, and Storage

Ideally, peanuts are harvested when the majority of the pods elicit a veined surface, have a colored seed coat, and three-quarters of the seed show darkening on the inner surface of the hull (see subhead Planting Date for more information) (Sanders et al.,

1982). Mechanical digging, shaking, and windrowing follow in the harvesting process.

Digging detaches the plant from the soil, shaking removes the excess soil, and windrowing inverts the plant, orienting its pods face upward allowing for curing.

Drying is one of the most important aspects of peanut quality. If the seeds are not dried to a safe moisture content (6-10%), quality deteriorates quickly and the probability of microbial invasion is increased (Sanders et al., 1982). Artificial drying of the seed should be done relatively soon after harvesting. This prevents mold and aflatoxin formation, and the formation of off-flavors caused from fungal lipase action and oxidative rancidity by decreasing water content of the seed. Drying temperature should not exceed 95oF with a moisture reduction rate of 0.5% per hour (Sanders et al., 1982).

Dried peanut seeds are normally stored as unshelled nuts at a relative humidity

between the ranges of 60 to 70%. The seeds should be stored in such a way that pest and

rodent invasion is not a problem. High temperatures during storage should also be

avoided.

Nutrition

From a nutritional standpoint, peanuts contain many of the essential vitamins and minerals necessary for proper health. Peanuts also contain roughly 50% fat, the majority being unsaturated. In comparison to other nuts, such as pecans and walnuts, peanuts contain less total fat (Maga, 1991). Peanuts containing high (>70%) oleic acid (18:1), a monounsaturated fatty acid, may also be useful in dietary regimes designed to reduce blood cholesterol levels in postmenopausal women, without resulting in problems associated with oxidation of low density lipoproteins (O’Byrne et al., 1997). A comparison of saturated fat in other foodstuffs is found in the following table (Table 2-1).

Table 2-1: Fat Comparison of Peanuts to Other Food Products

Food (serving size) Saturated Fat Total Fat Peanuts (28 g) 2.0 g 14 g Peanut Butter (30 g) 2.5 g 14 g Potato Chips (28 g) 3.0 g 10 g Egg Salad (84 g) 4.0 g 19 g American Cheese (28 g) 5.6 g 9 g Hamburger (96 g) 7.0 g 17 g * taken from the Peanut Advisory Council

Vitamins and minerals present in peanuts are found in the following table (Table 2-2).

Table 2-2: Vitamins and Minerals Present in Peanuts and Their Uses in the Body

% RDI in one Vitamins and ounce serving Minerals of dry roasted Uses in the Body peanuts Vital antioxidant, which protects Vitamin A and the Vitamin E 25% body’s cells and tissues from damage. It is important for the immune system and may aid in the prevention of tumor growth. Necessary for maintenance of healthy skin, the Niacin 19% nervous system, and digestive tract. Folate 10% Important for development of new cells in the body, particularly during periods of growth and during pregnancy. Thiamin (B1) 8% Needed to ensure normal functioning of the nervous system, appetite, and digestion Produces and breaks down proteins in the body and B6 4% manufactures red blood cells used to transport oxygen in the body Riboflavin Releases energy from the food we eat, helps skin (B2) 2% stay healthy, and assists in the normal functioning of the eye. Important in the building of bones and teeth, creation Magnesium 12% of protein, transmission of nerve impulses, and maintenance of body temperature. Copper 10% Important for the formation of hemoglobin, health of bones, blood vessels, and nerves. Phosphorous 10% Component of all soft tissues that is fundamental to growth, maintenance and repair of bones and teeth. Needed to ensure water balance in the body and Potassium 10% creation of protein. It also helps release energy from nutrients and aids in nerve impulse transmission. Aids in the formation of protein, wound healing, Zinc 6% blood formation, taste perception, appetite, night vision, and general growth and maintenance of all tissues. Iron 4% Aids in the transport and distribution of oxygen in the body’s cells. Calcium 2% Needed for the development and maintenance of healthy bones and teeth. * taken from the Peanut Advisory Council

Peanuts contain high levels of fiber, with naturally low sodium, are cholesterol- free, and represent a good source of folic acid. Peanuts also have chemical characteristics that parallel recent discoveries in nutrition that have been found to be beneficial to human health. Recently, resveratrol has received attention from the research community due to possible health benefits. Resveratrol was found in relatively moderate levels in muscadine grapes several years ago. Peanuts contain moderate levels of resveratrol, beta- stigmasterol, and behenic acid (Sanders and McMichael, 1999). The by-products of edible peanuts, such as the skin, contain behenic acid, which is used in cosmetics and shampoos.

Peanut Storage, Stability, and Oxidation

The term shelf life, in regard to peanuts or peanut oil, can be described as “the number of days before the onset of oxidative rancidity, a process which is generally induced in either the whole peanut or peanut oil by exposure to heat and air” (Mercer et al., 1990). This definition implies that the shelf life of peanuts is only as long as the time it takes before the onset of oxidative rancidity. The keyword here is the term rancidity, where a food becomes rancid or inedible. Rancid can be defined as “having the unpleasant taste or smell of oily substances that have begun to spoil” (Funk and Wagnall,

1997).

Peanut oil stability is quite good when compared to other vegetable oils, partly due to the fatty acid composition. Traditionally, runner-type peanuts contain approximately 50% fat or oil, which consists of 41-67% oleic acid (18:1n-9) and 14-42% linoleic acid (18:2 n-6). Because of the high amount of oil contained in a peanut, the quality can deteriorate quickly due to lipid oxidation, depending on a number of factors,

such as the presence of oxygen, light, moisture, and high temperatures. A factor of

interest involves the content and structure of the fatty acid constituents in the oil. As the

amount of double bonds increase in a fatty acid, it is more susceptible to oxidation.

Low levels of linolenic acid (18:3 n-6) in peanut oil are thought to be partially

responsible for oxidative stability, where the rates of oxidation are approximately

1:10:100:200 for 18:0, 18:1, 18:2, and 18:3, respectively (O’Keefe et al., 1993). Lipid

oxidation has been found to be a major source of the off flavors and decreased quality in

peanuts. Painty and cardboardy off flavors are formed during lipid oxidation, making the

product rancid and unacceptable to the consumer. The off flavors associated with painty

(pent-2-enal) and cardboardy (2t,2t-nonadienal) are formed over time from aliphatic

aldehydes in lipid systems, along with various other aldehydes and ketones (Grosch,

1982).

The oxidation occurring at double bond systems is thought to occur for a number

of reasons. Generally, autoxidation (the reaction with molecular oxygen through a self- catalytic mechanism) is noted as the primary cause of the quality defects that occur in lipid systems, due to hydroperoxide formation (Figure 2-1). This leaves the food product less acceptable because of off flavors and off odors created during oxidation.

Autoxidation starts by a term described as initiation. Initiation can be caused by the decomposition of hydroperoxides, metal catalysts, or light. Singlet oxygen, an excited state form of molecular oxygen, is thought to be the major contributing factor to initiation via free radical formation. This is commonly found in plant tissues containing chlorophyll, which is thought to be a sensitizer of singlet oxygen. Stable molecular oxygen (triplet oxygen) is not thought to attack the double bonds in lipid systems due to

the rules of spin conversion, since the carbon, carbon double bonds in carboxylic acids

are in singlet states. Once these free radicals are formed in the presence of lipids, attack

at the double bond systems is evident.

RH dimers; O 2 polymers; cyclic Initiation peroxides; ROO . hydroperoxy compounds Propagation

R .

RH cleavage

acyclic and cylclic ROOH

compounds aldehydes; ketones; hyroxycarbons; OH furans; acids ROOR; ROR . dimers RO

cleavage

aldehydes alkyl radicals semialdehydes or oxoesters

O2 condensation O2

terminal ROOH

hydrocarbons Hydrocarbons; Hydrocarbons; shorter aldehydes; aldehydes; acids; epoxides alcohols

* adapted from Nawar (1996)

Figure 2-1: Summary of Autoxidation in Food Systems

Propagation then takes place forming more peroxides and free radicals, increasing the rate of oxidation until the reaction must eventually slow or terminate due to the amount substrate available to form them.

Factors influencing the oxidative stability of peanuts include the handling, processing, and environmental conditions occurring during distribution. These factors, as mentioned above, include light contact to the seed, oxygen levels present during storage, the presence of metal catalysts, the moisture surrounding the peanut seed, and the amount of heat the seeds were exposed to (O’Keefe et al., 1993). Taking these factors into account is of great importance in peanut storage. Peanuts and peanut products would not be acceptable to consumers if they contained off flavors and/or off odors. Products of lipid oxidation, such as these, reduce peanut shelf life and decrease the profit margin of said products.

Peanut processors and handlers can use the theories of lipid oxidation previously outlined to increase shelf life. By minimizing the amount of oxygen contact (possibly by flushing with nitrogen and/or vacuum sealing), the amount of light exposure (by using brown glass or packaging material with minimal light passage), the amount of heat contact after roasting, the contact to metals such as copper, zinc, or iron, and storage at proper water activities, peanuts can be acceptable for consumption for an increased period of time.

Sensory

History and Uses

Psychophysics, the oldest discipline within experimental psychology, is the measurement of the relationship between physical stimuli and sensory experience

(Lawless and Heymann, 1998a). Several experimental psychologists, such as Bernoulli,

E. H. Weber, and G. T. Fechner, resolved laws concerning changes in sensory action and

stimulus.

An example of a psycophysical law is shown in the following Weber’s law:

∆ I = k I

where ∆ I is an increase in physical stimulus needed to be just noticeably different and I

is the starting level of stimulus.

Fechner’s law included a psychophysical relationship between intensity of

physical stimulus and sensory experience. This law proved quite useful in measuring

sensory response, and the theories behind it are still used today. Fechner’s law stated that

by adding the results from Weber’s law, a log function is the resultant when comparing

against measured sensory intensity. An example of Fechner’s law is as follows:

S = k log I where S is sensation intensity and I is the physical stimulus intensity.

This was the foundation for the method of limits, the method of right and wrong, and the method of adjustment (Lawless and Heymann, 1998a). These methods determined measurable levels for absolute thresholds, difference thresholds, and sensory equivalence, respectively. Many current sensory methods are based on these techniques and aided in the foundation of sensory sciences.

Testing

Today, methods for sensory testing can be found for just about any consumable

good. Specific methodologies and lexicons for flavor description for certain food

products allow us to measure the levels of separate, predominant flavors associated with

the product in question. These tests consist primarily of intensity rating scales, either using numbers or marks on a measured line, where the extremes of the line are given a

designation, such as very low and very high. Panelist training includes learning

definitions of certain flavor attributes, identification of the attributes in a sample, and

what its measured extreme levels are (i.e., high and low). Reproducibility testing

between individual panelists, after training, is key to ensure valid sensory evaluation.

Number scales, sometimes called ordinal scales, give a straightforward numerical representation of the data. Lower numbers signify lower intensities and higher numbers signify higher sensory intensities. An example of a number scale can be found in

Appendix A. By allowing a certain number of trained individuals to taste in accordance

to rules set forth in training panels, statistical relationships based on the mean response

for a particular attribute can be achieved. The differences and levels of the means allow

for separation of groups and give a good representation of sensory intensity that can be

correlated to other quantitative parameters.

Line scales also allow for numerical data analysis. Examples of line scale ballots

can be found in Appendices B and C. This requires the measuring of the sample from a

fixed point on a line. For instance, when using a 150-millimeter line scale, a mark

halfway along the line from the left would give a measured response of 75 millimeters.

This methodology has several advantages on ordinal scaling, based on ordinal scaling’s

fixed set of numbers. Line marking is less rigid, has more power, and contrasts

differences better than an ordinal scale (Lawless and Heymann, 1998b).

Peanut Flavor

Flavor attributes of peanuts in sensory studies are usually defined by seven characteristics: roast peanutty, woody/skins/hulls, raw/green/beany, cardboardy, sweet, salty, and astringent, according to Johnsen et al. (1988) regarding a lexicon for the description of peanut flavor. Other terms used in published literature include painty and fruity fermented for long-term storage and curing studies (Sanders et al., 1989b; O’Keefe et al., 1993). These descriptive terms correlate with the following definitions:

Roast peanutty–the classic, distinct flavor of a roasted peanut.

Woody/skins/hulls–a term used to describe the flavor of peanut skins or hulls.

Raw/green/beany–the term used to describe the rather bitter, raw flavor of an

unroasted peanut.

Cardboardy–a term used to describe the flavor or smell of cardboard. This unique

smell is the same as the taste that is received when masticating a cardboardy peanut. It is of particular importance to recognize this flavor when dealing with high-oleic peanut genotypes, as they tend not to reach the painty attribute (which will be described later) due to the oxidative stability that they posses. The formation of 2t,6t-nonadienal gives the characteristic cardboardy taste and smell formed during lipid autooxidation.

Sweet–the same taste that one receives by consuming moderate levels of sucrose

in solution.

Salty–the same taste that one receives by consuming moderate levels of sodium

chloride in solution.

Astringent–often confused with bitter, and might be compared to the taste of

walnut shells, roasted coffee beans or dark chocolate. It can be perceived as a dry feeling

18 in the mouth that may cause your mouth to pucker. Astringency and bitterness are not the same, but even trained sensory panelists have difficulties differentiating the two.

Painty–the taste in your mouth that you might receive when walking in a freshly latex-painted room. The smell gets into your nose, which correlates to the unique taste of a highly oxidized lipid. This flavor also comes from the formation of specific aldehydes

(pent-2-enal in particular), as it does in cardboardy flavor.

Fruity fermented–the flavor of a fermented product containing high amounts of esters. A flavor that is similar to this is the aftertaste of old moderately dark malt beers or out of date apple ciders. Sanders et al. (1989b) added this descriptor to a sensory panel for different maturities in cured peanuts.

Sweet and roast peanutty are considered positive attributes in describing ideal roast peanut flavor. Woody/skins/hulls, raw/green/beany, cardboardy, painty, astringent, and fruity fermented normally correspond to bad or negative flavors when describing fresh roasted peanuts.

Planting Date and Peanut Maturity

The main influence on the yield and quality of peanuts appears to be climate temperature during growth. A minimum of 2,600 growing degree-days (with a base of

13.3oC) is required for proper growth and development. Degree-days, or day-degrees, are thermal time units specific to the number of heat units acquired during a growing season

(Sanders et al., 1982). An example of the calculation is as follows:

Minimum daily temperature + Maximum daily temperature - 13.3OC 2

Precipitation, soil quality, seedbed or stand quality, pest management, virus control, and nitrogen fixing capability due to soil mineral deficiency, also play a part in

the yield and quality of the eventual seed produced (Ketring et al., 1982).

Drought conditions and cooler temperatures during the planting season, disease,

acreage, equipment, and personnel influence planting and harvest dates, which affect the

chances of harvesting at an optimal date. Optimum harvest date implies that most of the

seed harvested is mature, and of good quality. Functional planting dates vary from field

to field, depending on weather and other factors. Current investigations with planting

date, yield, fatty acid composition, and peanut flavor are being explored, one of which

can be found in Chapter 5.

Seed maturity is not always directly related to size in peanut seeds, however, the

larger seed from a plant tend to be the most mature. Some large pods may be immature

and some mature pods may be small. Hull scrape methodology is the current method of

analyzing for maturity (Sanders et al., 1982; Sanders and Bett, 1995). This method is

based on the color changes in the mesocarp and has been shown to be the most consistent

indicator of maturity and yield (Sanders et al., 1980; Pattee et al., 1981). By scraping the

outer hull from a peanut, a maturity profile of the plants can be generated by comparison

to a peanut profile board (a six column board with varying colors denoting maturity

levels) (Sanders, 1982).

Maturity has a significant effect on flavor potential in peanuts (McNeill and

Sanders, 1996; McNeill and Sanders, 1998, Mozingo et al., 1991; Pattee et al., 1995;

Sanders et al., 1989 a & b; Sanders and Bett, 1995). Planting date and harvest studies

show strong relationships in maturity and overall peanut quality, with no significant

20 relationship to pod size (McNeill and Sanders et al., 1996). McNeill and Sanders (1996) noted that peanuts from mature pods have greater flavor potential than those from immature pods. It was also noted that the fruity fermented flavor attribute developed more in the immature peanuts.

Overall oxidation and the formation of painty, sour, and bitter sensory attributes in Virginia-type peanuts were shown to be significantly higher in classes of immature peanuts (McNeill and Sanders et al., 1998). Sensory peanut flavor and sweet aromatic flavors were also significantly lower in the immature peanut classes. Formation of specific carbohydrates and free amino acids as peanuts reach full maturity could be the limiting factor in regards to peanut flavor potential (Pattee et al., 1995; Rodriguez et al.,

1989).

Moisture

One factor that influences the formation of peanut flavor is the measure of moisture level of the raw seed. Moisture control can be used as a prerequisite step to optimize roasting conditions from a manufacturing standpoint. Reasoning behind measuring moisture is based on the solvent properties of water as a vehicle for mobilizing chemical reactions in a food matrix. Moisture level can also be detrimental to the formation of certain flavor compounds if the moisture level is too high, resulting in a dilution effect on the reactant molecules causing formation.

Several studies involving the moisture contents of peanuts have been investigated.

These studies have shown that several parameters in roasting and roast peanut flavor are affected by initial moisture content and moisture content during roasting. For example, the initial rate of temperature increase in peanuts of lower moisture content is higher than

21 peanuts with higher initial moisture content (Chiou et al., 1989). Further studies from

Chiou et al. also noted that moisture loss is more rapid in higher levels of initial moisture than lower initial moisture levels during roasting (Chiou et al., 1991).

Initial moisture also relates to color formation in roasted peanuts. Peanuts with higher moisture contents tend to give darker color than those with lower initial moisture contents, reducing potential flavor quality, when roasted under the same conditions

(Chiou et al., 1991; Pattee et al., 1982). Moisture content also plays a role in proteins during roasting, lipid peroxidation, and shelf life of peanuts (Chiou et al., 1989; Evranuz,

1993).

Color Development

Applications

Color measurements can be made in a number of ways. These measurements are usually made by the measure of light reflectance and are expressed as an L-value.

Samples are placed in a machine calibrated against black and white tiles supplied by the manufacturer of the equipment and the resultant values are scaled on a measure of 0-100, where 100 is the white calibration standard and 0 is the black standard.

Automated methods of color measurement have been used for the last 20 years to measure quality of peanut butter and roast color of peanuts to produce the unique roasted flavor found in roasted peanuts by measuring the reflectance of a peanut sample, giving an L-value as the unit of measurement. CIELAB and Hunter color schemes use a reflectance value of L in color determination of peanuts. This is a simple method and is a good indicator of roast flavor. However, there are differences in roasted peanut flavor and roast color between genotypes of peanuts.

Theory

Color development in peanuts is dependent on the creation of brownish-colored polymeric compounds known as melanoidins. Melanoidins are water-insoluble, high molecular weight compounds (several thousand Daltons) formed via Maillard (carbonyl- amine) browning products that correspond directly to color development in foods (Ames et al., 1994). However, most melanoidin compounds do not necessarily contribute to flavor and aroma (Rizzi, 1994). Temperature, heating time, pH, and moisture content play major roles in the formation of colored melanoidin compounds (Ames et al., 1994).

As the temperature of roasting increases (for a given time), the final color appears darker due to the formation of higher molecular weight melanoidins formed during heating

(Ames et al., 1994). Color tends to develop faster at higher pH's in low moisture systems and the reverse is seen in aqueous systems (Ames et al., 1994; Reineccius, 1990;

Lingnert, 1990). Maillard reaction rates tend to reach a maximum in intermediate moisture systems, but are highly dependent on the system temperature (Lingnert, 1990).

For example, the concentration of Amadori compounds (necessary intermediates in the formation of color and flavor in the Maillard reaction) increase much faster at higher temperatures with large differences at low moisture. On the other hand, smaller changes are observed as the water content of the system increases (Eichner and Schiurmann,

1994).

Isolation and structure determination of melanoidins have almost exclusively been derived from aqueous model systems with a single amino acid and a single sugar, yielding few structures confirmed (Ames et al., 1994). It is universally thought that most reactions in foods simultaneously form color and flavor compounds by a variety of

pathways, giving a mixture of melanoidins and volatile substances responsible for roasted

characteristics in a given matrix (Reineccius, 1990).

Water Activity

Water activity is a term used to describe the relationship between the intensity of

the association of non-aqueous constituents with water (Fennema, 1996). Typically,

water activity of a food product is measured to determine its perishability by microbial

means, but does play a major role in the formation of compounds in chemical reactions.

One of the multitude of reactions that water activity plays a role in is lipid oxidation.

Oxidation of lipids is influenced by a number of factors, one being water activity or

percent relative humidity. Water activity is defined as the relative vapor pressure of the solute above a sample divided by the vapor pressure of pure water (at the same temperature) based on Raoult’s Law, p/po, and are expressed as a number from zero to one. Percent relative humidity is the water activity multiplied by 100.

Lipid oxidation is, in part, dependant on the vapor pressure surrounding a food matrix and tends to be problematic for long-term food storage. Lower (0.0 – 0.2) and higher (0.6 - 1.0) water activities generate oxidative by-products at higher rates than near the monolayer values (0.33 – 0.42) in model systems (Labuza, 1975). An example of water activity and its effects on lipid oxidation are found in Figure 2-2.

Water activity plays an important role in the oxidation of peanuts in packaged confectionary products as some processors reported shelf lives as short as seven weeks.

Intermediate water activity lessens oxidative rancidity in stored peanuts and walnuts

(Mate et al., 1996). Not only does water activity play a role in oxidation, it also affects sensory crispness, crunchiness, and textural changes in snack foods and breakfast cereals,

24 as well as color and flavor formation under roasting conditions (see color development)

(Katz and Labuza, 1981; Lingnert, 1990; Sauvageot and Blond, 1991).

*taken from Nawar, 1996

Figure 2-2: Water Activity and Rate of Oxidation

Formation of Peanut Flavor

Peanut Roasting

Peanut roasting and the development of color and roasted flavor in peanuts has been a topic of research for some time. Typically, roast color is the most important quality control parameter in commercial processes (see Color Development). Roast color in peanuts is generally measured by light reflectance in a colorimeter, giving an L-value in a range from 80 (very light or no roast) to 30 (very dark roasted). The Hunter L-value of roasted peanuts used in high quality dry roasted peanuts and peanut butter falls in the range of 50-51 (Sanders et al., 1989a).

Thermodynamic modeling of continuous, cross-flow roasters was established in the latter part of the 1990’s (Landman, 1994, Landman et al., 1994). This process

25 describes the heat and mass transfer as a model for peanut roasting. Color development alone does not account for the flavor constituents of a particular variety of peanut, as the substrate for melanoidin and pyrazine development may be different from variety to variety, based on the sugars and free amino acids present in the peanut seed.

Pyrazine Development

In roasted foods, pyrazines or alkylpyrazines are formed via Maillard reactions above 700C, and directly contribute to roasted or cooked flavors (Maga and Sizer, 1973).

Formation of roasted flavor components in peanuts is especially apparent when peanut seeds are heated above 1300C (Landman, 1994). Pyrazines play a roll in the flavor when roasting peanuts, coffee beans, sesame seeds, barley, cocoa, popcorn, potato products, rye crisp bread and beef. Below is an example of an unsubstituted pyrazine, a six-carbon ring with nitrogen atoms at the one and four positions:

Figure 2-3: An Unsubstituted Pyrazine

Of all the products formed during the Maillard reaction, pyrazines are the most widely studied. These Strecker Degredation products account for well over 100 papers published since the 1950’s. Many mechanisms for pyrazine formation have been postulated in models systems, but the complex nature of a food system, coupled with a multitude of reactions occurring simultaneously, do not allow scientists to measure all reactions taking place and their final products with currently available technology. This is to say that the final identified pyrazines formed during heating could come from several mechanisms, and any one particular postulated mechanism for their formation in peanuts is inconclusive.

Pyrazines isolated in peanuts and their corresponding odor threshold ranges, to date, are found in the following tables (Tables 2-3 and 2-4):

Table 2-3: Pyrazine Compounds Found in Peanuts

Pyrazine Propylpyrazine 2-methylpyrazine 2-methylpropylpyrazine 2,3-dimethylpyrazine 2-methyl-6-propylpyrazine 2,5-dimethylpyrazine Isopropylpyrazine 2,6-dimethylpyrazine Methylisopropylpyrazine Dimethylpyrazine 2-isopropenylpyrazine Trimethylpyrazine Methylpropenylpyrazine 2-ethylpyrazine Vinylpyrazine 2-ethyl-3-methylpyrazine 2-methyl-5-vinylpyrazine 2-ethyl-5-methylpyrazine 2-methyl-6-vinylpyrazine 2-ethyl-6-methylpyrazine Ethylvinylpyrazine 2-ethyl-3,5-dimethylpyrazine Acetylpyrazine 2-ethyl-3,6-dimethylpyrazine 5-acetyl-2-methylpyrazine 3-ethyl-2,5-dimethylpyrazine 6-acetyl-2-methylpyrazine 3-ethyl-2,6-dimethylpyrazine 6-acetyl-2-ethylpyrazine 5-ethyl-2,3-dimethylpyrazine 6,7-dihydro-5H-cyclopentapyrazine 2,3-diethyl-3-methylpyrazine 2-methyl-6,7-dihydro-5H- 2,6-diethyl-3-methylpyrazine cyclopentapyrazine Diethylpyrazine 5-methyl-6,7-dihydro-5H- Diethyldimethylpyrazine cyclopentapyrazine 2,3-diethyl-5-methylpyrazine 2(3),5-dimethyl-6,7-dihydro-5H- 2-ethyl-3,5,6-trimethylpyrazine cyclopentapyrazine *taken from Maga, 1982

Table 2-4: Odor Thresholds and Odor Descriptors of Selected Pyrazines (ppb) in Water

Compound Threshold (ppm) Odor Description Methylpyrazine 60,000 – 150,000 Roasted 2,3-dimethylpyrazine 2,500 Roasted, Nutty 2,5-dimethylpyrazine 1,800 – 35,000 Roasted Methoxypyrazine 700 Not distinct 2-methoxy-3-methylpyrazine 4 Nutty, Roasted Peanuts trimethylpyrazine 9,000 Roasted Chicken *adapted from Maga, 1982

Roasted flavor impact in peanuts is thought to come primarily from 2- methylpyrazine and isomers of dimethylpyrazine (Mason et al., 1966; Warner et al.,

1996).

The formation of pyrazine compounds are known to be caused from reactions involving amino acids and sugars via the Maillard reaction. The Maillard reaction, or carbonyl-amine browning reactions, was first proposed by Louis Camille Maillard in

1912. This complex scheme was further studied by Hodge (1953) and is still not fully elucidated. The following figure (Figure 2-4) represents one of the many schemes for the formation of Maillard products:

*taken from Fujimaki et al., 1985

Figure 2-4: Maillard Reaction Pathway

During heating of foodstuffs, amino-carbonyl precursors are formed by the liberation of free sugars and free amino acids. A reversible Schiff base is formed in the food matrix, followed by the products of the irreversible Amadori rearragement. The products of the Amadori rearrangement undergo a number of reactions, including dehydration, oxidation, cyclization, and scission (Fujimaki et al., 1985).

Of the countless number of reactions that take place in the formation of Maillard reaction products, several have been studied extensively. Pyrazine formation mechanisms have been studied over the past 40 years, and an example of a mechanism for substituted pyrazines is found in Figure 2-5 below:

O O Sugars + amino acids

R1 R2

Strecker Degredation

R1 R1

CHNH C=O 2 Condensation Oxidation C=O CHNH2

R2 R2

N N R R R R 1 1 1 1

R2 R2 R2 R2 N N

R1 and R2 = H, CH3, CH2CH3 *adapted from Hodge, 1953

Figure 2-5: Proposed Alkylpyrazine Formation by Maillard Reactions

Peanuts, when heated, develop a unique, desirable, roasted peanut flavor.

Roasting time and temperature play a roll in the formation of peanut flavor and influence intensity of flavor and odor in roasted peanuts (Buckholtz et al., 1980). According to

Newell et al. (1967), free sugars and free amino acids were the major precursors to roast peanut flavor. These precursors form pyrazines and carbonyls via Maillard type reactions that contribute heavily to roasted peanut flavor (Mason et al., 1966; Newell et al., 1967;

Walradt et al., 1971). Alkylpyrazines formed in low moisture, amino acid-carbohydrate model systems, are thought to be the major constituents involved in roasted peanut flavor

(Koehler and Odell, 1970).

Conversion of sucrose to fructose and glucose and/or formation of comparable reductones appear to be the major mechanism in regards to carbohydrates involved in this reaction (Mason et al., 1966). This was also seen in work done by Chiou et al. (1991), where glucose contents were higher after 10 minutes of roasting than in raw peanuts.

Aspartic acid, asparagines, glutamic acid, glutamine, histadine, and phenylalanine are amino acids thought to be associated to the typical flavor in peanuts (Newell et al.,

1967). Peptide-2 (an unknown compound) was found to contribute greatly to roasted flavor, when hydrolyzed during roasting (Mason et al., 1969). This peptide, found in ample amounts in peanuts, is hydrolyzed when heated to form necessary amino acid reactants. Peptide-2 was also shown to increase as peanuts mature (Mason et al., 1969).

Solid Phase Microextraction (SPME)

In 1991, Janusz Pawliszyn and colleagues invented a new method of headspace extraction called solid phase microextraction (SPME). SPME was originally named after an experiment that used an SPME device, where solid fused-silica fibers were used as the

30 extraction medium. It was later renamed to reference the appearance of the extraction phase and its relation to a liquid or gaseous donor phase, even though it is not always technically a solid, as in the case of polymeric coatings such as polydimethylsiloxane

(Pawliszyn, 2000). The idea behind this method involved the use of subsitituted siloxane coatings similar to the stationary phased found in capillary gas chromatography attached to a plastic fiber, allowing for partitioning of molecules in liquid and air. It eliminates the use of costly organic solvents, significantly shortens the time of analysis, and allows for automation of sample preparation and extraction. Process monitoring, on-site analysis, analysis of target analytes, measurement of pesticide residues are just a few of the many applications of SPME. An example of a portable SPME device is located below in

Figure 2-6.

*taken from Pawlisyn, 2000

Figure 2-6: SPME Extraction / Desorption Process

This technique has been applied to the extraction of solid, air, and water matrices, with great success, if certain care is taken in selecting various parameters mentioned below.

The basic principle of SPME uses a small amount of extracting phase, even when the sample volume is quite large, such as the headspace of air around a sample, or a large body of water (i.e. a lake). Extraction media to date are polymeric coatings on a fused silica fiber, such as polydimethylsiloxane (PDMS), divinylbenzene (DVB), carboxen, or mixtures of thereof. In the headspace extraction approach, a partitioning equilibrium between the sample matrix and the extraction phase is reached. Heating the sample matrix can accelerate equilibrium. This device can be used in an autosampler, making sample extraction automated and much less labor intensive than other volatile extraction methodologies. Within the simplicity of the extraction mechanism, theories behind

SPME are based on more traditional volatile extraction techniques. The impression that the extraction is a simple, trivial process is not necessarily true. Since the fundamental processes involved in SPME are similar to traditional techniques, successful method development is correlated to selection of a number of parameters. The nature of the target analytes and the complexity of the sample matrix determine the level of difficulty in accomplishing successful extractions of volatile constituents.

The mass of an analyte extracted by the polymeric coating is related to the overall equilibrium of the analyte in a three-phase system: the fiber coating, the gas phase or headspace, and a homogeneous matrix such as pure water or air. Currently, partitioning equilibrium is limited to the liquid polymeric phases available for extraction, such as a

PDMS fiber. Constant porosity of the sorbent is necessary, since the total surface area

32 available for adsorption is proportional to the coating volume. At very high analyte concentration, it is necessary to take into account that saturation of the surface can occur, resulting in non-linear isotherms (Pawliszyn, 1999).

To ensure good accuracy and precision, the following steps should be considered in method development: selection of the fiber coating, selection of an agitation technique, selection of a separation and/or detection technique, optimization of the desorption conditions, optimization of the sample volume, determination of the extraction time, calculation of a distribution constant, optimization of the extraction conditions, determination of the linear dynamic range of the method, and selection of the calibration method.

Precision of the method can be affected by agitation conditions, sampling time

(especially if non-equilibrium conditions are used), temperature of the sample, sample volume, headspace volume, vial shape, condition of the fiber coating (cracks or adsorption of high molecular weight species can greatly affect target analyte absorption), geometry of the fiber (thickness and length of the coating), sample matrix components

(such as salt or humidity), time between extraction and analysis, analyte loss (through the septa or a large injection port liner), condition of the injector (pieces of septa), moisture in the needle, and stability of the detector response (Pawliszyn, 1999).

In summary, peanut flavor is influenced by a number of factors (planting date, harvest date, genotype, storage conditions, fatty acid composition, and roasting methods).

Reasearch involving these factors greatly enhances our knowledge of the changes and reactions involved in preparing high-quality peanut products for human consumption.

CHAPTER 3

STORAGE WATER ACTIVITY EFFECTS, OXIDATION, & SENSORY PROPERTIES OF HIGH OLEIC PEANUTS

Introduction

Peanuts (Arachis hypogaea L.) are economically important in many countries with India, China, and the United States being the major producers. Peanuts contain about 50% fat, of which about 80% is unsaturated. Oleic and linoleic acids account for the majority of the total unsaturated fatty acids in typical peanut. Although linoleic acid is essential for humans, it is susceptible to lipid oxidation (Nawar, 1996). In the presence of oxygen, light, moisture, and high temperatures, oxidation of fatty acids can occur

(Nawar, 1996) and has been found to be a major source of off-flavors and decreased quality in peanuts (Ory et al., 1985).

High oleic peanuts have been developed at the University of Florida having >81% oleic acid and <3% linoleic acid (Gorbet and Knauft, 1997). In comparison, typical peanuts have 50% oleic acid and 30% linoleic acid (Braddock et al., 1995). Oxidation of linoleic acid occurs about ten times faster than oleic acid (Nawar, 1996) and, as a consequence, high oleic, low linoleic peanuts have improved oxidation resistance

(Braddock et al., 1995; Mugendi et al., 1997).

SunOleic 97R was released by UF to replace SunOleic 95R. SunOleic 97R not only surpasses olive oil in oleic acid content, but it yields from 10 to 14 percent more peanuts per hectare than some other runner peanut genotypes (Gorbet and Knauft, 1997).

33 34

Using Sunoleic 97R instead of normal oleic peanuts should result in significantly longer

shelf life of peanut-containing products (Gorbet and Knauft, 1997; Mugendi et al., 1998) and this could translate into significant economic savings. High oleic peanuts may also be useful in dietary regimes designed to reduce blood cholesterol levels in postmenopausal women, without resulting in problems associated with oxidation of low

density lipoproteins (O’Byrne et al., 1997). SunOleic 97R is less suseptible to Tomato

Spotted Wilt Virus (TSWV) than SunOleic 95R, but not suitable for high pressure

(TSWV) production situations (Gorbet and Knauft, 1997).

Lipid oxidation has been correlated to water activity (aw) in many foods (Le

Maguer, 1987; Leung, 1987; Rahman, 1995). Chemical and sensory properties of stored peanuts may be affected by aw of storage. Maximization of peanut shelf-life requires a

knowledge of the relative loss of textural and flavor quality during storage at different aw.

The objective of this work was to determine the effects of storage aw on stability and

quality changes in roasted high-oleic peanuts.

Materials and Methods

Sample Preparation and Storage

High oleic peanuts (SunOleic 97R) were obtained from the University of Florida's peanut breeding program. Triplicate samples of peanuts were sized and dry roasted in a tumble roaster to a HunterLab “L” color value of 50-51 (Sanders et al., 1989a).

Triplicate samples of peanuts were stored in glass dishes in 273 X 311mm plastic desiccators, containing saturated salt solutions at 250C, in order to obtain the water

activity values: lithium chloride (0.12), hydrated magnesium chloride (0.33), potassium

carbonate (0.44), hydrated magnesium nitrate (0.52), cupric chloride (0.67) (Rahman,

1995). The saturated salt solutions were maintained by stirring and additional salts were added to ensure saturation weekly. The aws were verified using a relative humidity meter

(Fisher Scientific, Pittsburgh, PA).

Lipid Extraction and Peroxide Value Determinations

Lipid was extracted, in duplicate, from the high oleic peanuts using a modified

Bligh and Dyer extraction according to Christie (1982). The Official American Oil

Chemists’ Society [AOCS] method was used to measure peroxide values and results

reported as milliequivalents peroxide/kg oil (AOCS Cd 8-53).

Sensory Analysis

Sensory analysis was conducted at 0, 2, 4, 6, 8, 10, and 14 weeks of storage.

Eleven trained panelists (6 male, 5 female) consisting of students and staff of the Food

Science Department who had previous experience on peanut sensory panels were used throughout the course of the study. Panelists were trained in 3 thirty-minute sessions before the beginning of the study. During training, panelists were provided with samples of freshly roasted peanuts and peanuts that had been stored to result in several levels of oxidation (Braddock et al., 1995; Mugendi et al., 1998). The sensory attributes selected and used by the panelists were roast peanut, crunchy, sweet, cardboardy, and painty, using a 9-point scale. At each testing session, a reference sample was given as a control

to anchor roasted peanut flavor. The control was a fresh roasted peanut sample stored at

–20 °C in glass jars flushed with nitrogen. Panelists were given three grams of peanuts

per sample, and were provided with unsalted crackers and distilled water. Sample order

and sample coding were randomized. Each of the five water activity treatments were

evaluated at each session and panelists took a ten-minute break in between replications.

The attributes were rated on a 9-point scale with one represented by low intensity of each

attribute and nine representing high intensity. All panels were performed in duplicate.

An example of the ballot used can be found in the index.

Statistics

A randomized complete block design was used (Rao, 1998) and the data was analyzed by analysis of variance (ANOVA) using SAS (Cary, NC), using attribute = treatment|time|panelist replication as the model statement. Means were separated using a

Duncan’s Mean Separation test when a significant F-value was obtained. Response surface plots were constructed using Statistica for windows (version 4.5, Statsoft, Tulsa

OK).

Moisture

The moisture of the stored peanuts was determined, in triplicate, using the AOAC

Official Method 925.40 (moisture in nuts and nut products). The moisture content

immediately after roasting was between 2% and 3% for all samples (wet weight basis).

Sorption Isotherms

Moisture sorption isotherms were generated in triplicate by plotting mean

moisture content against storage water activity (Figure 3-9).

Results and Discussion

Moisture

The peanut moisture content increased under all storage conditions (Figure 3-1) and ranged between 1% and 7%. The moisture was still increasing for all samples even at 14 wk of storage. Even at the lowest storage aw (0.12), moisture increased from about

2% to almost 4% by week 14. Roasted peanuts are clearly hygroscopic, and readily pick

up moisture even at extrememly low aw. Experimentally generated sorption isotherms show a moisture content of roughly 3 to 5% moisture content for peanuts stored at 0.33–

0.44 aw over the course of storage.

Peroxide Values (PVs)

The PVs increased over time for all storage conditions (Figure 3-2). The range of peroxide values was 2-9 meq/kg. The PV increases were not linear and the humidity of storage affected the PV after about 4 weeks of storage. The PVs increased in aw order

from 0.33>0.44=0.52>0.12=0.67. The main effects of time and aw were highly significant (p<0.01). The effect of water activity on oxidation rates agree with other

studies where the lowest rate of oxidation has been found at intermediate water activities

(Labuza, 1975).

Sensory Analysis

The roast peanutty scores decreased significantly (p<0.05) with time (Figure 3-3).

Sensory scores began around 7 (on a 9-point scale) and ended between 4.8 (0.12 aw) and

2.4 (0.67 aw). The peanutty intensity was maintained best at lowest water activity. This

could be due to either lower oxidation resulting in lower amounts of aldehydes that mask

peanut flavor (Warner et al., 1996) or less loss of pyrazines (Braddock et al., 1995).

Pyrazines are considered to be the major flavor compounds in peanuts and coffee (Maga,

1991). The crunchiness sensory ratings also decreased, with the greatest loss also found

at 0.67 aw, followed by 0.53 then the other treatments (Figure 3-4). Loss of crunchiness

was mostly eliminated by storage at aw at 0.44 and lower. Moisture content versus

crunchiness correlations can be found in Table 3-1.

Cardboardy (Figure 3-5) and painty (Figure 3-6) scores increased with time. The efffect of aw on cardboard and painty sensory scores was relatively small. Although there

was a trend for the highest two aws to have higher painty and cardboardy scores during

storage, this was not observed at each of the storage times. The PV changes did not correspond to equivalent changes in peanutty or cardboard/painty off flavors.

Correlations for peroxide value (PV) are found in Table 3-1. Extending storage times may result in more clearly defined differences in these sensory attributes. Previous work has shown that the differences in sensory attributes only become apparent when the peroxide values of the high oleic peanuts exceed ten (Mugendi et al., 1998; Braddock et

al., 1995). Thus, although peroxide values are markedly affected by aw, the sensory

ratings are not clearly affected.

The results of the oxidation and sensory analyses indicate that higher aw results in

loss of sensory crunchiness, and that a high level of crunchiness can be maintained by

storage at 0.44 aw or lower. Sensory mean separations are available in Table 3-2. There was significant (p<0.05) negative correlation between sensory crunchiness and moisture content of the stored peanuts (Figure 3-7). The moisture content of the peanuts was affected by the time and aw of storage (Figure 3-1), and even at very aw (0.12), peanuts

gained moisture and lost crunchiness over storage. These results indicate that it may be

very difficult to maintain maximum crunchiness in peanuts incorporated into food

products that have even intermediate aw.

Panelists noted on sensory ballots that cardboardy sensory scores above 5 were

unacceptable. No sensory scores above five were obtained until 10 wk of storage for any

aw. Peanuts stored at aw between 0.33 and 0.52 never reached a sensory score of 5 for the

39 off flavors during the fourteen-week storage period. Mean separations during storage can be found in Table 3-3.

In previous studies with the high oleic peanut, cardboardy scores were usually higher than painty scores throughout sensory evaluation (Mugendi et al., 1996). Because of the oleic/linoleic acid ratio of the high oleic peanut, cardboardy sensory scores are more pronounced than in typical runner peanuts. This is presumably due to lower production of hexanal and higher nonanal in high oleic peanuts (Braddock et al., 1995).

Panelists noted on sensory ballots that painty sensory scores above four were unacceptable. The first painty scores above four were found after ten weeks of storage at aw 0.12. After 14 weeks, sensory painty scores of four or greater were found in high oleic peanuts stored at 0.52 and 0.67 aw, where 0.67 aw was the only storage condition to achieve a painty score greater than five.

Conclusions

Roasted high oleic peanuts maintain best product quality (low oxidation, loss of crunchiness and maintenance of desirable flavor) when stored at water activities between

0.33 and 0.44. Above this range, crunchiness decreased and oxidation increased, whereas below the rate of oxidation increased.

Figure 3-1: Moisture Changes During Storage at Various Water Activities

Figure 3-2: Peroxide Values During Storage at Various Water Activities

Figure 3-3: Roast Peanutty Flavor During Storage at Various Water Activities

Figure 3-4: Crunchiness During Storage at Various Water Activities

Figure 3-5: Cardboardy Flavor During Storage at Various Water Activities

Figure 3-6: Painty Flavor During Storage at Various Water Activities

Sensory Crunchiness 3

1 2345678 Moisture (%)

Figure 3-7: Crunchiness and Moisture Content Correlation

5 0.12 0.33 4 0.44 0.52

% Moisture 3 0.67

0 0 2 4 6 8 10 12 14 Weeks of Storage

Figure 3-8: Change in Moisture During Storage at Various Water Activities

2 weeks 5 4 weeks 6 weeks 4 8 weeks 10 weeks 3 14 weeks kg water / solid 2

0 0.00 0.10 0.20 0.30 0.40 0.50 0.60 Water Activity

Figure 3-9: Moisture Sorption Isotherms For High Oleic Peanuts

Table 3-1: Statistics for Sensory Parameters

r (X,Y) r-square t p N PV vs. Cardboardy 0.7742 0.5994 6.473 5E-07 30 PV vs. Painty 0.7287 0.5310 5.630 5E-06 30 Moisture Content vs. Crunchy -0.7676 0.5891 -6.879 7E-07 35

Table 3-2: Duncan’s Mean Separation for Sensory Ratings and Storage Water Activity

Water Activity Attribute 0.12 0.33 0.44 0.52 0.67 A1 B1 C1 D1 E1 Roast peanut (5.1) (4.6) (4.9) (4.0) (3.5) A2 B2 B2 C2 D2 Crunchiness (6.1) (5.5) (5.5) (4.2) (3.4) A3 B3 B3 C3 D3 Sweetness (4.4) (4.0) (4.1) (3.7) (3.4) A4 B4 B4 C4 C4 Cardboardy (5.9) (3.4) (4.1) (4.4) (4.9) A5 A5 A5 B5 B5 Painty (3.4) (3.5) (3.5) (4.0) (4.5) *means within a row followed by the same letters are not significantly different

Table 3-3: Duncan’s Mean Separation for Sensory Ratings During Storage

Storage Time (weeks) Attribute 0 2 4 6 8 10 14 A1 B1 C1 C1 D1 D1 D1 Roast peanut (7.5) (6.1) (4.7) (4.5) (3.7) (3.7) (3.7) A2 B2 C2 D2 E2 E2 E2 Crunchiness (7.3) (6.7) (5.3) (4.3) (3.3) (3.5) (3.4) A3 B3 C3 D3 E3 F3 E3 Sweetness (5.8) (4.8) (4.5) (3.8) (3.9) (3.3) (3.8) A4 A4 B4 C4 D4 E4 DE4 Cardboardy (0.8) (1.9) (3.3) (3.8) (4.9) (5.8) (5.4) A5 A5 B5 C5 D5 D5 E5 Painty (0.9) (1.7) (2.9) (3.6) (4.1) (4.3) (5.4) * means within a row followed by the same letters are not significantly different

CHAPTER 4 DETERMINATION OF PYRAZINES AND FLAVOR CHANGES IN PEANUTS DURING ROASTING

Introduction

The study of peanut flavor has been an ongoing challenge since the early 1950’s

(Hodge, 1953). Reactions involving formation of typical roasted peanut flavor compounds and their corresponding precursors have yet to be fully elucidated. Pyrazines, volatile heterocyclic nitrogen containing compounds, are thought to be the major flavor compounds eliciting typical roasted peanut flavor (Mason et al., 1966; Maga, 1973;

Koehler and Odell and Odell, 1970; Shibamoto and Bernhard, 1977). Over 70 pyrazine have been isolated from peanuts and studies have shown strong correlations to peanut flavor and pyrazine detection levels (Maga, 1982).

Measurements of color and/or moisture are valuable methods for determining quality in roasted peanuts. Currently, the quality standard used in industrial settings to determine roast peanut flavor is based primarily on the roast color of the seed or the change in moisture content after heating. Previous studies involving roasted peanut flavor note that there are a number of factors that affect peanut flavor, regardless of color

(Buckholtz et al., 1980; Chiou et al., 1991; Chung et al., 1993; Smyth et al., 1998).

Variety, maturity, planting date, and improper curing and drying do not significantly change seed color after roasting, but are involved in development of roasted peanut flavor. By measuring pertinent volatile compounds in peanuts, one can establish how

46 47 variable roasting parameters effect roasted peanut flavor. Peanut roasting could be optimized for roasted peanut flavor by measuring volatile compounds present in a finished product, in addition to current measurements such as moisture or color.

When attempting to find optimal time / temperature combinations of peanut roasting, a multitude of different methods are presented that do not directly relate to peanut flavor. Time, temperature, and variations in roasting (i.e. oil roasting, dry roasting, etc.), affect the final product flavor. However, trial and error in roasting conditions were the basis for early peanut product manufacturers. The majority of roasting methods used in the peanut industry today are proprietary or a trade secret for a particular company, and thus not available for final product comparison.

Attempts to quantify peanut volatiles have been made by a number of investigators (Buckholtz et al., 1980; Chiou et al., 1991; Koehler and Odell, 1970; Mason et al., 1966; Warner et al., 1996). The majority of the methods involved in these studies used some sort of heating to separate the volatile compounds from the non-volatile constituents of the peanut, mainly via distillation. Heating in this manner could cause changes in pyrazine levels, thermal conversion of pyrazine compounds to other isomers, or concentration / loss of volatile compounds during transfer (Pawlizyn, 2000). Until recently, methods such as these were the only methods available to the investigator for volatile analysis.

In 1990, solid-phase microextraction (SPME) was introduced to the scientific community by Pawlisyn and collegues. SPME allows investigators to easily extract and separate headspace volatiles by the use of substituted siloxane coatings attached to a plastic fiber, thus partitioning molecules in liquid and air (Pawlizyn, 2000). SPME

eliminates the use of costly organic solvents, significantly shortens the time of analysis,

and allows for automation of sample preparation and extraction. This technique can be

successfully applied to the extraction of solid, vapor, and aqueous matrices if certain care

is taken in selecting various parameters prior to analysis. Techniques such as capillary

gas chromatography coupled with SPME can give a “fingerprint” of volatile compounds

in a food matrix. With information derived from trained sensory panels and changes in

corresponding flavor compounds in peanuts, optimized peanut roasting can be established

for a number of sensory attributes, including roasted peanut flavor.

The objective of this study was to determine if SPME is a feasible method for

measuring changes in roasted peanut volatiles, and if so, how they correspond with

sensory perception of roasted peanut flavor. With this information, optimization of

roasting parameters in peanuts and peanut products could be established for any level of

roasted peanut flavor.

Materials and Methods

Sample Preparation and Storage

Four peanut genotypes were used in this study, FMDR ’98, a mid oleic variety;

Florunner, a normal oleic variety; Georgia Greene, a normal oleic variety; and SunOleic

97R, a high oleic variety. Peanut yields, shelling, and grading was done at the University of Florida Agricultural Experiment Station in Marianna, Florida. The peanuts were sent to the University of Florida, Gainesville, for further analysis. Prior to roasting, the peanuts were stored at –200C in nitrogen-flushed, sealed plastic Hefty One-Zip Slider©

(Lake Forest, IL) freezer bags for 2 months.

Peanut Roasting

Raw, shelled peanuts were removed from frozen storage, allowed to equilibrate to room temperature after 12 hours, and roasted using a Pyrex forced air convection oven

(Aroma AeroMatic Oven, San Diego, CA). Approximately 50 grams of peanuts were placed near the outside of a stainless steel basket, which was raised to the center of the

Pyrex bowl, in order to optimize the temperature and air flow to be uniform and consistent throughout the chamber. The peanuts were roasted at 1250C, 1500C, 1750C, and 2000C for 5, 10 and 15 minutes. Extreme levels at 5 and 10 minutes for 1250C and

10 and 15 minutes for 2000C were omitted due to unacceptable roast quality ascertained from preliminary studies. Time and temperature were monitored using a digital laboratory thermocouple and digital stopwatch (Component Design, Portland, OR). The thermocouple was placed on the outside of the stainless steel basket, measuring the temperature of the air surrounding the peanut seed. Temperature control of the forced air convection oven was monitored throughout roasting and adjusted according to the thermocouple readings (± 50C). After roasting, the peanuts were transferred to 250 mL screw-top glass jars, and nitrogen flushed. Immediately after flushing, tops were fitted with Parafilm and stored at –200C until sensory panels were conducted.

Sensory Analysis

A trained 16 person (9 male, 7 female) sensory panel consisting of students and staff of the Food Science and Human Nutrition Department were used to evaluate the peanuts. The majority of the panelists had previous experience on descriptive peanut sensory panels. The panelists were trained in four 1-hour sessions in the Food Science

and Human Nutrition Department Taste Panel Room before the beginning of the study.

The sensory attributes rated were roast peanut flavor, roast peanut aroma, sweetness, raw/green/beany, bitterness, and crunchiness. All attribute intensities were described to

the panelists and examples were given to iterate attribute levels in accordance to Johnsen

et al. (1989). Once the panelists were familiar with the attributes to be analyzed in the

study, they were asked to rate fresh roasted and various stored roasted peanuts of

differing genotypes and roast levels. Tests and training were conducted until all members

of the panel were consistent when given blind samples to rate on a line scale.

All attributes were rated on a 150-millimeter line scale, where the far left end of

the scale (0 mm) was denoted as none and the far right, high (150 mm). All stored

peanuts were equilibrated to room temperature before sensory evaluation. Panelists were

given approximately three grams of peanuts per sample in separate booths under red

lighting. Each of the four genotypes was evaluated for all 8 roasting levels at separate

panels, in duplicate. The order of presentation for each variety can be found in Table 4-1.

Sample order and sample coding were picked at random for each panel. A balanced

incomplete block statistical design was used and the data analyzed by analysis of

variance. The balanced incomplete block design was conceived using the order of

presentation found in Table 4-1. Sample order randomization was based on panelist

number, where no panelist received the same panelist number for any variety (separate

panel) tested. Panelists were presented with ample amounts of water at each taste session

for palate rinsing. The panelists were required to take a ten-minute break between

duplicate samples, and were given a different order of presentation to maintain blind

sampling. An example of the ballot used can be found in Appendix B.

Table 4-1: Balanced Incomplete Block Design for Panelist Presentation

Panelist 1 Panelist 2 Panelist 3 Panelist 4 Panelist 5 Panelist 6 Panelist 7 1 8 2 5 2 1 2 2 3 4 6 4 4 3 3 4 6 7 5 6 5 4 7 8 8 7 7 8 Panelist 8 Panelist 9 Panelist 10 Panelist 11 Panelist 12 Panelist 13 Panelist 14 1 3 1 1 1 1 2 3 4 2 3 2 4 3 6 5 5 5 7 5 6 8 6 6 7 8 8 7

Key for Block Coding 125C for 15 minutes= 1 175C for 5 minutes= 5 150C for 5 minutes= 2 175C for 10 minutes= 6 150C for 10 minutes= 3 175C for 15 minutes= 7 150C for 15 minutes= 4 200C for 5 minutes= 8

Roast Color

Hunter L, a, and b color values of the roasted peanuts were determined using a

Colorguard colorimeter (BYK-Gardner, Columbia, MD), calibrated by standard laboratory practices. All samples were allowed to equilibrate to room temperature before measurement.

Moisture

The moisture of the stored peanuts was determined in triplicate using the AOAC

Official Method 925.40 (moisture in nuts and nut products) using a mechanical convection oven (Precision Scientific, Winchester, VA).

Solid Phase Microextraction (SPME)

External Standard Preparation

Samples of 2-methylpyrazine, 2-methoxypyrazine, 2,3-dimethylpyrazine, 2,5- dimethylpyrazine, 2,3,5-trimethylpyrazine, and 2-methoxy-3-methylpyrazine were obtained from Aldrich Chemical Co, Milwaukee, WI. All pyrazines tested were greater

52 than 98% purity according to the manufacturer. A primary standard of the six pyrazines was made in a 40 mL vial fitted with caps containing polytrifloroethelene septa (Fisher

Scientific, Pittsburgh, PA). Pyrazine concentrations were prepared at different levels, taking special care to significantly change concentrations of compounds that may elute closely during separation. Concentrations for each pyrazine are denoted in table 4-2.

Table 4-2: Selected Primary Pyrazine Concentration for Standard Curve

Selected Pyrazine ppm 2-methylpyrazine 1.20 2-methoxypyrazine 1.00 2,5-dimethylpyrazine 2.00 2,3-dimethylpyrazine 4.19 2-methoxy-3-methylpyrazine 2.89 2,3,5-trimethylpyrazine 6.59

The primary pyrazine standard was diluted with deionized water 10 times to give concentrations ranging from 1 ppm to 100 ppm. The serial dilutions were then used to construct separate linear regressions for each of the six pyrazines in the standard using the same SPME/GC/FID procedures described below, in order to quantify pyrazines in the roasted peanuts. The corresponding R2 values of the derived linear regressions can be found in Table 4-3.

Table 4-3: Linear Regression Equations and R2 values for External Pyrazine Standard

Selected Pyrazine Regression Equation R2 2-methylpyrazine y=181.4x 0.9941 2-methoxypyrazine y=681.7x 0.9869 2,5-dimethylpyrazine y=428.6x 0.9904 2,3-dimethylpyrazine y=458.6x 0.9851 2-methoxy-3-methylpyrazine y=1339x 0.9780 2,3,5-trimethylpyrazine y=1102x 0.9702

The headspace was sampled using an polydimethylsiloxane/divinylbenzene

(PDMS/DVB) SPME fiber and fiber assembly (Sigma-Aldrich, Milwaukee, WI) for each of the mixed pyrazine standard dilutions, allowing the fiber to equilibrate in the headspace of a 40 mL screw top vial fitted with polyethylene septa placed in a 600C

water bath (Fisher Scientific Isotemp Model 210, Pittsburgh, PA). Preliminary studies

were required in order to set temperatures and times for SPME adsorption and desorption.

New pyrazine compounds are not typically formed below 700C and increased

temperature increased the speed that headspace equilibrium is reached, thus a water bath

temperature of 600C was used for headspace sampling. Headspace equilibration of the

sample was determined by sampling the headspace using SPME over a period of time.

Once there is no longer an increase in peak area over a given period of time, then the

sample is said to be at equilibrium. Equilibrium was reached in this study after 13

minutes in a 600C water bath (Figure 4-1).

After the SPME fiber had reached equilibrium, the samples were analyzed by gas chromatography (GC) using a flame ionization detector (FID) (Shimadzu GC 14A,

Norcross, GA) and a DB-5 column (J&W Scientific, Folsom, CA). Pyrazines were separated by increasing the temperature from 600C (3 min. hold time) to 800C (4 minutes

hold time), ramped at two degrees per minute. Injection port and FID port temperature

was 2000C. Thermal desorption took place for three minutes in the injection port.

Thermal desorption time was determined from preliminary studies for this method. This

step was repeated in quadruplicate for each of the pyrazine standard dilutions. Linear

regressions and R2 values were calculated for each pyrazine using Microsoft Excel

(Microsoft Corporation, Bellevue, WA). All R2 values were above 0.90.

SPME Equilibrium

100 90 80 70 60 50 40 30

Relative peak area % 20 10 0 0 2 4 6 8 10 12 14 Time (min)

Figure 4-1: SPME Equilibrium

Sample Preparation

Five grams of whole roasted, shelled peanuts were chopped in a Cuisinart Mini-

Prep food processor (East Windsor, NJ) to a homogeneous size (~1-2 mm diameter) and transferred to 40 mL vials fitted with caps containing polytrifloroethelene septa, in triplicate. All peanuts were equilibrated to room temperature before addition to the vial.

The vials containing the chopped, roasted peanuts were shaken for one minute and allowed to settle, while sealed. Sample vials were then transferred to a 600C water bath for 30 minutes prior to sampling. The PDMS/DVB SPME fiber was then inserted into the vial via the septa, exposing the fiber to the headspace of the roasted peanut sample for

15 minutes before removal, to ensure headspace equilibrium. Thermal desorption for 3 minutes in the injection port was required in order to remove all compounds on the fiber.

Resultant areas from identified pyrazines were compared to linear regressions

generated by the external standard, giving concentrations in parts per million for each

pyrazine. Concentrations were averaged over the three replications for data analysis.

Results and Discussion

Table 4-4 shows the main effects of roasting time and temperature on peanut

aroma, peanut flavor, sweetness, rawness, bitterness, and crunchiness. Means for peanut

aroma and flavor did not separate at the two lowest roasting levels (1250C/15 min. and

1500C/5 min.) for all genotypes, but did show differences at higher roast levels (1750C/15

min. and 2000C/5 min). The largest changes in aroma and flavor occurred at 1750C

between 10 and 15 minutes, indicating a more rapid change in roasted peanut attributes

when heated at this temperature. This implies that slight changes in time at temperatures

typical to current “cookbook” peanut roasting conditions greatly effect sensory

perception of aroma and flavor. Peanut aroma and flavor showed the same trends in

mean separation, suggesting that aroma and flavor are similar in the sensory perception of

peanuts.

Peanuts roasted at 1750C/10 minutes and 1750C/15 minutes gave the lowest sweetness scores for all peanut genotypes. This agrees with previous studies involving flavor formation in peanuts. As sucrose hydrolyzes to glucose and fructose during roasting, both reducing sugars are used as precursors to pyrazines via carbonyl-amine browning reactions, which may decrease sweetness as roasted flavors increase (Chiou et al., 1989 and 1991). Raw, bitter, and crunchy sensory attributes did not indicate major differences as a function of roasting parameters, but raw flavor shows inverse relationships to roasted peanut aroma and flavor, bitterness increases when at longer

periods at higher temperatures, and crunchiness is inversely related to moisture, and

agrees with previously published data (Chiou and Tsai, 1989 and 1991; Sanders and Bett,

1995; Rodriguez et al., 1989)

Duncan’s mean separations for sensory analysis are found in Table 4-5 for all

roasting parameters for each peanut variety separately, and are discussed in more detail in

the following text. Figures 4-9 to 4-14 show differences in least-squares means and

Figures 4-15 to 4-26 linear relationships at 1500C and 1750C for Florunner, Florida MDR

98, Georgia Greene, and SunOleic 97R. These relationships accommodate for average

variation as a function of linear time / temperature combinations.

In mean separations conducted by variety (Table 4-5), roasted aroma tended to

separate from other roasting conditions between 1250C for 15 minutes to 1500C for 5

minutes, 1500C for 10 minutes to 1750C for 5 minutes, and 1750C for 10 minutes to

2000C for 5 minutes. The best example of separation can be found in peanut aroma for

Florida MDR 98 (Table 4-5). Peanut flavor and aroma showed similar trends in the

Florunner variety, with the highest levels found at the 1750C/15 minute roasting parameter (124.9 for aroma and 125.9 for flavor). Similar results were obtained in the

Florida MDR 98 variety.

Sensory means for Florunner were similar to the Florida MDR 98 variety in regard to roasted flavor and aroma at temperatures under 2000C, but never reached the

intensity of Florida MDR 98 when roasted under the same conditions. Sugar differences

in Florunner and Florida MDR 98 have yet to be elucidated, but increased levels of

overall sugar concentration or particular reducing sugars present in Florida MDR 98 may

possibly account for its increased flavor potential. However, Florida MDR 98 showed the

highest bitterness sensory score when roasted at 1750C for 15 minutes (Table 4-5 and

Figure 4-13).

Similar trends in sensory perception of flavor and aroma were apparent in Georgia

Greene and SunOleic 97R, with the exception of roasting at 1500C for 10 minutes in

Georgia Greene, which exhibited significantly higher response (Figure 4-9 and 4-10).

SunOleic tended to show the lowest overall roasted peanut flavor and aroma for all roasting conditions, contrary to other work done in the peanut area. This can be seen in the comparison between aroma and flavor Figures 4-9 through 4-10. There is a possibility that aldehydes formed by either lipid oxidation or Maillard reactions (in the form of Strecker aldehydes), act upon the system in the same way, or otherwise in tandem. If this is true, then high-oleic peanuts could have less potential of forming valuable precursors to color and flavor via Maillard browning and subsequent pyrazine formation, thus making more thorough heating of high-oleic peanuts necessary for comparable flavor and color in comparison to normal-oleic lines.

Hunter L-values for SunOleic 97R showed no significant differences in comparison to Florunner and Florida MDR 98, although it showed significantly lower flavor at comparable heating levels, indicating that further examination of color and its relationship to roasted aroma and flavor formation is necessary (Figure 4-7). This is also apparent in the Georgia Greene variety, which shows lower color development, but with little difference in roasted peanut flavor and aroma (Table 4-5). Color means significantly separated by Duncan’s as a function of roasting conditions (Table 4-6), but changes were slight for each variety and their corresponding roasting levels (Figure 4-7).

Florunner L-value means during roasting separated for each level, with the exception of roast levels 3 and 5, and the interaction between 1 and 2, and 4 and 8 (refer to table 4-1 for roast level relationships). The lightest colors were observed at roast level

2 and the darkest colors at roast level 7 (Table 4-6). Florunner L-value correlations to peanut aroma and flavor had R2 values of 0.763 and 0.790, respectively (Table 4-7).

L-value means did not show significant differences between roast levels 1 through

3, 4 through 5, and 7 and 9 for Florida MDR 98 (Table 4-6). Roast level 7 fully separated from the rest of the means, having a significantly lower L-value (darker color) than the other roasting conditions. Florida MDR 98 L-value correlated to roasted aroma and flavor, having the highest R2 values of the genotypes tested (Table 4-8). The lowest and

highest L-values were similar to the Florunner variety.

Georgia Greene L-value means separated by roast level, with the exception of

levels 1 and 2, and the interaction of levels 3 and 4, and 5 and 8. Roast level 1 had the

highest L-value, where roast level 7 had the lowest (Table 4-6). L-value significantly

correlated with Georgia Greene’s peanut aroma and flavor (Table 4-9).

Means separated in SunOleic 97R, with the exception of 1, 3, and 5, and 7 and 8.

Interactions were observed between the means of roast level 2 and levels 1, 3, 4, and 5.

The highest L-values observed were found in level 1, and the lowest in level 7, following

the same general trends involved in the other genotypes. SunOleic 97R’s L-values

significantly correlated to roasted peanut flavor and aroma (Table 4-10).

In accordance to the previously mentioned results regarding roast color and

flavor, direct measurement of known flavor compounds formed in peanuts during heating

is a valuable asset as to the prediction of roasted flavor and aroma. Methylpyrazine and

2,5-dimethylpyrazine showed the greatest changes during roasting for all genotypes

(Figures 4-2 to 4-5). 2,5-dimethylpyrazine was detected for all roast levels above 1500C

for 10 minutes. Formation of pyrazine compounds tended to be at their highest under all

roasting conditions in Florunner and Florida MDR 98 (Figure 4-6), agreeing with the

sensory evaluation of peanut aroma and flavor.

For the Florunner variety, the highest levels of methylpyrazine and 2,5-

dimethylpyrazine were observed at 1750C for 15 minutes. (Figure 4-2 and Table 4-6). In the Florida MDR 98 variety, pyrazine levels were slightly higher at 1750C for 15 minutes of roasting than Florunner, however not significantly different.

Differences in pyrazines were noticed for Georgia Greene and SunOleic 97R genotypes, which had significantly lower overall pyrazine formation than the Florunner and Florida MDR 98 (with the exception of roasting at 1500C for 10 minutes for Georgia

Greene). High-oleic peanuts have been shown to have lower flavor development and

may account for the lower levels of pyrazines observed (Warner et al., 1996), in contrast

to work done by Pattee et al. (1995) which stated no significant differences between

Florunner and SunOleic 97R. Further work on SunOleic 97R and other peanut genotypes

should be done to examine the cause of flavor phenomena as a function of fatty acid chemistry. Georgia Greene (a normal-oleic variety) shows similar trends to the high-

oleic SunOleic 97R variety. These differences in pyrazine level agree with sensory

results regarding peanut aroma and flavor in Florunner and Florida MDR 98 (Figure 4-6),

again showing a stronger relationship to sensory perception than color measurement.

The pyrazine isomer, 2,5-dimethylpyrazine separated 6 out a possible 8 roast

levels for Florunner and Georgia Greene, suggesting that it may also be a valuable

predictor of sensory flavor and aroma in peanut processing operations (Table 4-6). In

Florida MDR 98 and SunOleic 97R, 2,5-dimethylpyrazine showed 5 levels of separation and a stronger correlation with roast peanut flavor and aroma than L-values and, thus, remains a candidate for monitoring roasted flavor and aroma when measuring a single

pyrazine during peanut roasting.

Sweetness scores showed a negative correlation to roasted flavor for all genotypes

tested (Tables 4-7 to 4-10). Raw scores show an inverse relationship with roast flavor.

Roasted aroma and roasted flavor attributes correlated very highly to one another with an

R2 of 0.9830.

In the Florunner peanut variety, 2-methylpyrazine, 2,5-dimethylpyrazine, 2,3-

dimethylpyrazine, 2,3,5-trimethylpyrazine, and total pyrazines all showed strong, significant, negative correlations to L-value (Table 4-7). L-value also showed high correlation to roasted aroma and flavor, as well. As expected, roasted aroma and roasted flavor showed the strongest correlations to one another. Roasted aroma showed the strongest correlation to 2,5-dimethylpyrazine. Roasted flavor, on the other hand, showed a slightly stronger correlation to 2,3,5-trimethylypyrazine by a slight margin. However, it is this investigators opinion that since the changes in 2,5-dimethylpyrazine are greater than in 2,3,5-trimethylypyrazine and L-value, that 2,5-dimethylpyrazine would be a better marker in the measurement of roasted Florunner peanuts. Equations showing the statistical model for Florunner in coded and actual forms can be found in Table 4-11.

These models can act as “predictors” in the SPME quantitation of pyrazines, L-value, roasted peanut flavor and aroma.

Pyrazines 2-methylpyrazine, 2,5-dimethylpyrazine, 2,3-dimethylpyrazine, 2,3,5- trimethylpyrazine, and total pyrazines followed strong, negative correlations to L-value, and positive correlations to sensory aroma and flavor for Florida MDR 98. As in

Florunner, roasted aroma and flavor correlated very highly and showed an R2 of 0.978

(Table 4-8). Pyrazines 2,5-dimethylpyrazine and 2,3,5-trimethylpyrazine showed

stronger correlations and a higher R2 than L-value for roasted aroma and flavor, where

2,3,5-trimethylpyrazine showed the strongest correlation in Florida MDR 98. Florida

MDR 98 did not show a significant inverse correlation in flavor and sweetness.

Prediction equations are found for Florida MDR 98 in Table 4-12. 2,5-dimethylpyrazine

again showed strong correlation to roasted aroma and flavor and appears to be an

excellent predictor for sensory quality.

Pyrazines 2-methylpyrazine, 2,5-dimethylpyrazine, 2,3,5-trimethylpyrazine, and total pyrazines all showed stronger correlations with roasted flavor and aroma and better fit than L-value for the Georgia Greene variety (Table 4-9). 2,5-dimethylpyrazine showed the strongest relationship of the aforementioned pyrazines. Once again, roasted aroma and flavor correlated extremely well. 2,3-dimethylpyrazine did not show a significant relationship to flavor and aroma. Table 4-13 shows equations that may be used in prediction of 2-methylpyrazine, 2,5- dimethylpyrazine, total pyrazines, L-value, roasted aroma, and roasted flavor for Georgia Greene in coded and actual statistical

models.

Significant correlations between roasted aroma and flavor are observed in 2-

methylpyrazine, 2,5-dimethylpyrazine, 2,3,5-trimethylpyrazine, and total pyrazines for

SunOleic 97R (Table 4-10). Pyrazines 2,5-dimethylpyrazine and 2,3,5-trimethylpyrazine

showed the highest significant correlation to roasted flavor and aroma in the SunOleic

97R genotype, with 2,5-dimethylpyrazine edging 2,3,5-trimethylpyrazine slightly. 2,3-

dimethylpyrazine was not significantly correlated with roasted aroma and flavor.

Roasted flavor and aroma highly correlated to one another in SunOleic 97R. Prediction

equations for SunOleic 97R can be found in Table 4-14 in coded and actual models for 2-

methylpyrazine, 2,5-dimethylpyrazine, total pyrazines, L-value, roasted aroma, and

roasted flavor.

Moisture levels did not show any significant trends (Figure 4-8 and Table 4-6).

Moisture as a quality aspect is involved primarily in the desirable crunchiness of the seed.

Although peanut processors use moisture content as a valuable parameter, it is essentially

measured to indicate possible crunchiness (Chiou et al., 1991). Several publications

agree that moisture content is involved in the formation of roasted flavor and aroma, but

in most circumstances it is not as readily involved in the formation of volatile compounds

as other parameters, such as maturity (Chiou et al., 1991; Evanruz, 1993).

2,5-dimethylpyrazine showed the strongest correlations to roasted flavor for every

variety, adding further that when choosing a single pyrazine in correlation to flavor

development, 2,5-dimethylpyrazine may be the compound of choice when roasted above

1500C. Prediction equations (Table 4-11 to 4-14) could also be used to estimate the temperatures and times necessary to establish roasted aroma, roasted flavor, pyrazine levels, and color.

Although many of the volatile compounds mentioned are associated with roasted peanut flavor, simple combinations of these compounds do not duplicate the complex sensory properties of the roasted seed itself, and therefore, sensory analysis must be done

63 to produce a desirable product. This is due to the commercial acquisition of peanut seeds sold by size or a certain seed count per unit weight. Consequently, roasting operations must use a raw material, which is a mixture of genotypes, seed sizes and maturities, seed developmental environments, and seed curing and storage histories. Thus, all of the previously mentioned variables play a role in roasted peanut flavor potential, which make it difficult to provide a simple method to predict roasted flavor and/or aroma in roasted peanuts.

The methods commonly in use today to determine volatile compounds in foods are simultaneous purging and solvent extraction, which takes 3 days, and static headspace extraction which is a 2-hour labor-intensive process (Pawliszyn, 2000). Extraction of volatiles with static headspace extraction techniques require the headspace to be withdrawn over a 3 minute period as to not disturb the headspace that much. This requires a bit more guesswork, especially when done by hand. Given the parameters that change roasted flavor potential in the raw seed, an optimal method is out of the realm of possibility, but the inclusion of a rapid way to measure peanut aroma and flavor would help speed the optimization of roasting conditions for a given lot of seed. A rapid prediction of roasted flavor by measuring pyrazine content, possibly with the inclusion of color and moisture, would invariably aid peanut processors in producing a consistent, high quality product.

Conclusions

SPME/GC/FID is a rapid, non-destructive method for determining pyrazine levels in peanuts. Pyrazines correlated highly with roasted peanut flavor and aroma. 2,5- dimethylpyrazine may be the best overall pyrazine to measure as a predictor of roasted

64 peanut flavor and aroma, due to high correlation coefficients, although 2,3,5- trimethylpyrazine seems to be a good indicator as well, especially in the case of Florida

MDR 98. Pyrazine correlations (2,5-dimethylpyrazine in particular) slightly edged L- value for the majority of the genotypes, allowing for increased accuracy in the measure of peanut aroma and flavor.

Roasting at 1750C for 15 minutes gave the highest sensory scores for roasted peanut flavor and aroma, the highest levels of total pyrazines, and the lowest L-values for all genotypes tested. Peanut genotypes differ in roasted flavor and aroma, regardless of roast color. Inclusion of pyrazine levels allows for more accurate optimization of roasting parameters when measuring roasted peanut quality.

F 125/15 50 F 150/5 F 150/10 F 150/15 40 F 175/5 F 175/10 PPM Pyrazine 30 F 175/15 F 200/5

0 2-mepyr 2,5-DMP 2,3-DMP 2-mox-3-me 2,3,5-TMP Selected Pyrazines

* Lines above bars denote standard deviation ** 2-mepyr = 2-methylypyrazine, 2,5-DMP = 2,5-dimethylpyrazine, 2,3-DMP = 2,3- dimethylpyrazine, 2-mox-3-me = 2-methoxy-3-methylpyrazine, 2,3,5-TMP = 2,3,5- trimethylpyrazine

Figure 4-2: Pyrazine Levels for Florunner at Various Roast Levels *

40 M 125/15 M 150/5 M 150/10 M 150/15 30 M 175/5 M 175/10

PPM Pyrazine M 175/15 20 M 200/5

0 2-mepyr 2,5-DMP 2,3-DMP 2-mox-3-me 2,3,5-TMP Selected Pyrazines

Figure 4-3: Pyrazine Levels for Florida MDR 98 at Various Roast Levels *

G 125/15 25 G 150/5 G 150/10 G 150/15 20 G 175/5 G 175/10 PPM Pyrazine 15 G 175/15 G 200/5

0 2-mepyr 2,5-DMP 2,3-DMP 2-mox-3-me 2,3,5-TMP Selected Pyrazines

Figure 4-4: Pyrazine Levels for Georgia Greene at Various Roast Levels *

S 125/15 25 S 150/5 S 150/10 S 150/15 20 S 175/5 S 175/10 PPM Pyrazine 15 S 175/15 S 200/5

0 2-mepyr 2,5-DMP 2,3-DMP 2-mox-3-me 2,3,5-TMP Selected Pyrazines

Figure 4-5: Pyrazine Levels for SunOleic 97R at Various Roast Levels *

120

100

80 125/15 150/5 150/10 150/15 60 175/5

Total PPM 175/10 175/15 40 200/5

0 Florunner FMDR98 Georgia Green SunOleic97R Variety

* Lines above bars denote standard deviation **FMDR98 = Florida MDR 98, Georgia Green = Georgia Greene, SunOleic97R = SunOleic 97R

Figure 4-6: Total Pyrazines for Genotypes at Various Roast Levels *

125/15 150/5 40 150/10 150/15 175/5 30 175/10

Hunter L-values 175/15 200/5 20

0 GG SO 97R Florunner FMDR 99 Variety

* Lines above bars denote standard deviation **FMDR98 = Florida MDR 98, Georgia Green = Georgia Greene, SunOleic97R = SunOleic 97R

Figure 4-7: Hunter L-values for Genotypes at Various Roast Levels *

125/15 150/5 150/10 150/15 3 175/5 175/10 % moisture 175/15 200/5 2

0 Georgia Green Florunner FMDR SunOleic Variety

* Lines above bars denote standard deviation **FMDR98 = Florida MDR 98, Georgia Green = Georgia Greene, SunOleic97R = SunOleic 97R

Figure 4-8: Moisture Content for All Genotypes After Roasting

Table 4-4: Main Effects of Roasting Treatments (Averaged Across All Genotypes) on Sensory Attributes *

Peanut Peanut Sweetness Raw Bitterness Crunchiness Aroma Flavor Peanut 125C/15 min E (34.16) E (32.57) A (68.97) A (77.16) C (46.31) D (77.33) 150C/5 min E (39.55) E (39.71) A (70.91) B (64.71) CD (34.39) BCD (84.14) 150C/10 min D (68.16) D (62.11) A (67.57) C (39.09) CD (36.52) CD (81.50) 150C/15 min C (92.80) C (92.66) B (54.73) DE (25.13) CD (38.64) ABC (87.27) 175C/5 min D (74.00) D (69.34) A (74.27) CD (31.50) D (30.68) BCD (82.82) 175C/10 min AB (111.84) AB (115.09) C (43.27) E (14.77) AB (72.09) AB (87.34) 175C/15 min A (121.95) A (120.68) C (36.55) E (12.54) A (76.87) AB (91.14) 200C/5 min B (106.80) B (108.32) B (53.30) E (18.48) B (62.93) A (94.0) *Means within a column followed by the same letter are not significantly different (Duncan’s multiple range test, 5%)

Table 4-5: Effects of Roasting Time and Temperature on the Sensory Attributes of Peanut Genotypes *

Florunner Aroma Flavor Sweet Raw Bitter Crunchy 125C/15 min A (41.64) A (40.71) A (72.43) A (64.43) A (22.57) A (78.29) 150C/5 min A (44.29) A (41.64) A (67.21) A (57.36) A (28.21) BC (94.71) 150C/10 min B (87.93) B (84.07) A (63.64) B (29.64) BCD (46.14) BC (95.21) 150C/15 min BC (101.6) BC (99.71) B (42.00) B (24.07) AB (37.93) BC (93.86) 175C/5 min B (83.21) B (81.50) A (73.14) B (16.14) A (26.00) AB (83.79) 175C/10 min BC (105.8) CD (115.5) B (44.36) B (10.21) BCD (56.07) AB (81.50) 175C/15 min C (124.9) D (125.9) B (38.71) B (14.79) CD (64.79) C (100.1) 200C/5 min BC (102.4) CD (108.9) B (43.71) B (15.79) D (71.57) C (106.3) FMDR Aroma Flavor Sweet Raw Bitter Crunchy 125C/15 min A (43.88) AB (37.69) AB (61.06) A (64.44) AB (42.63) AB (81.25) 150C/5 min A (36.86) A (33.93) BC (76.86) A (73.14) B (32.29) A (78.43) 150C/10 min B (63.57) BC (56.71) AB (65.79) BC (27.36) B (37.86) AB (86.64) 150C/15 min B (72.93) D (77.14) AB (66.21) B (31.14) AB (44.71) ABC (90.14) 175C/5 min B (78.00) CD (71.43) C (94.00) BC (16.57) B (24.86) BC (97.93) 175C/10 min C (111.4) E (122.5) A (50.64) BC (20.14) CD (79.86) ABC (93.86) 175C/15 min C (117.0) E (120.1) D (29.14) C (6.143) C (95.43) ABC (90.86) 200C/5 min C (124.3) E (124.3) A (49.25) BC (22.08) AD (64.75) C (105.3) Ga. Gr. Aroma Flavor Sweet Raw Bitter Crunchy 125C/15 min A (27.14) A (27.00) A (67.00) A (79.29) AB (72.57) ABC (75.21) 150C/5 min B (54.71) B (53.71) A (62.43) AB (63.79) B (50.21) C (87.86) 150C/10 min BC (65.93) B (60.79) B (85.29) C (41.79) C (16.50) AB (72.07) 150C/15 min D (104.6) CD (112.6) A (55.36) D (18.93) BC (41.64) BC (83.07) 175C/5 min C (72.71) B (66.64) A (66.57) BC (53.50) BC (40.21) A (68.14) 175C/10 min DE (117.0) CD (112.9) C (36.29) D (4.79) A (88.43) C (90.27) 175C/15 min E (126.6) D ( 118.5) C (31.93) D (8.21) AB (68.07) BC (82.71) 200C/5 min D (101.6) C (96.57) A (53.86) D (18.93) AB (56.86) BC (86.14) SO97R Aroma Flavor Sweet Raw Bitter Crunchy 125C/15 min A (22.57) A (24.14) A (76.50) A (102.3) AB (48.00) A (74.00) 150C/5 min A (22.36) AB (29.57) A (77.14) B (64.57) A (26.86) A (75.57) 150C/10 min B (55.21) BC (46.86) BC (55.57) B (57.57) AB (45.57) A (72.07) 150C/15 min C (92.07) D (81.21) BC (55.36) C (26.36) A (30.29) A (82.00) 175C/5 min B (62.07) C (57.79) AB (63.36) BC (39.79) A (31.64) A (81.43) 175C/10 min CD (113.2) E (109.4) C (41.79) C (23.93) BC (64.00) A (83.71) 175C/15 min D (119.3) E (118.3) BC (46.43) C (21.00) C (79.21) A (90.93) 200C/5 min CD (101.4) E (105.9) AB (65.79) C (25.93) BC (58.79) A (80.21)

SO97R=SunOleic97R

* Means within a column followed by the same letter are not significantly different (Duncan’s multiple range test, 5%)

Table 4-6: Effects of Roasting Time and Temperature on Pyrazines, L-value, and Moisture *

Florunner 2-mepyr 2,5-DMP 2,3-DMP 2-meox-3 2,3,5-TMP Pyr Total L-value Moisture 125C/15 min A (0.000) A (0.000) A (0.000) AB (0.364) A (0.234) A (0.598) AB (64.65) A (4.795) 150C/5 min A (0.000) A (0.000) A (0.000) A (0.000) A (0.000) A (0.000) A (66.41) A (4.869) 150C/10 min A (0.000) B (5.550) B (0.606) A (0.000) B (0.888) B (7.044) BC (61.78) AB (3.270) 150C/15 min B (2.752) C (9.795) A (0.000) AB (0.569) B (1.152) C (14.27) CD (59.17) AB (3.495) 175C/5 min B (5.244) D (15.73) A (0.000) A (0.000) C (1.760) D (22.73) BC (61.01) AB (3.289) 175C/10 min C (27.06) E (47.69) C (1.000) C (1.786) D (4.767) E (82.30) E (51.20) B (2.574) 175C/15 min D (38.88) E (49.66) D (1.636) B (0.764) E (5.548) F (96.49) F (44.65) B (2.497) 200C/5 min E (13.66) F (33.28) BC (0.877) B (0.916) F (4.227) G (52.97) D (57.04) B (3.018) Florida MDR 98 2-mepyr 2,5-DMP 2,3-DMP 2-meox-3 2,3,5-TMP Pyr Total L-value Moisture 125C/15 min A (0.000) A (0.000) A (0.000) A (0.305) A (0.340) A (0.650) A (66.71) A (2.357) 150C/5 min A (0.000) A (0.000) A (0.000) A (0.062) A (0.000) A (0.060) A (66.37) B (2.873) 150C/10 min A (1.625) AC (7.718) A (0.000) B (0.632) AB (0.766) AC (10.74) A (66.61) C (1.779) 150C/15 min A (2.641) BE (24.32) A (0.124) B (0.613) CD (2.473) BC (30.17) B (62.31) D (1.207) 175C/5 min A (1.390) AC (9.673) A (0.000) A (0.072) ABD (1.169) AC (12.30) B (60.13) D (1.399) 175C/10 min B (13.03) B (26.23) B (1.085) CD (0.927) C (3.501) B (44.67) C (52.05) E (0.781) 175C/15 min C (37.19) D (49.17) C (1.607) BC (0.725) E (5.704) D (94.40) D (44.75) E (0.623) 200C/5 min B (5.731) CE (13.50) A (0.000) D (1.129) BD (1.958) AC (22.32) C (52.73) E (0.819) Ga. Green 2-mepyr 2,5-DMP 2,3-DMP 2-meox-3 2,3,5-TMP Pyr Total L-value Moisture 125C/15 min A (0.000) A (0.000) A (0.000) BD (0.883) A (0.000) A (0.883) A (65.50) A (4.198) 150C/5 min A (0.000) A (0.000) A (0.000) A (0.000) A (0.000) A (0.000) A (64.79) B (5.196) 150C/10 min A (0.000) B (5.161) A (0.000) BD (0.872) B (0.588) B (6.620) B (61.77) CD (3.204) 150C/15 min B (4.904) C (9.979) A (0.000) A (0.000) C (0.841) C (15.72) BC (60.92) C (3.500) 175C/5 min B (4.908) C (10.18) A (0.000) B (1.017) CD (1.049) C (17.15) D (58.56) C (3.451) 175C/10 min C (11.74) D (19.63) B (0.634) C (0.405) D (1.280) D (33.69) E (54.68) D (2.839) 175C/15 min D (24.89) E (32.88) C (1.239) D (0.695) E (3.064) E (62.77) F (45.07) C (3.361) 200C/5 min E (9.837) F (16.22) A (0.000) E (1.687) F (1.697) F (29.44) CD (59.47) C (3.524) SO97R 2-mepyr 2,5-DMP 2,3-DMP 2-meox-3 2,3,5-TMP Pyr Total L-value Moisture 125C/15 min A (0.000) A (0.000) A (0.000) A (0.000) A (0.000) A (0.000) A (64.06) AD (4.027) 150C/5 min A (0.000) A (0.000) A (0.000) A (0.000) A (0.000) A (0.000) AB (62.25) B (5.007) 150C/10 min A (0.000) B (2.723) A (0.000) A (0.000) B (1.425) B (4.148) A (62.67) AC (4.445) 150C/15 min B (2.430) C (6.022) A (0.000) B (0.345) C (0.580) C (9.378) B (60.19) BC (4.651) 175C/5 min A (0.000) B (3.540) A (0.000) A (0.000) D (0.860) B (4.400) A (62.83) D (3.695) 175C/10 min C (10.32) D (20.50) B (0.861) C (0.584) E (3.399) D (35.67) C (49.68) E (2.484) 175C/15 min D (27.76) E (32.82) C (1.007) C (0.590) E (3.563) E (65.74) C (47.61) E (2.337) 200C/5 min C (9.843) D (22.20) A (0.000) A (0.000) F (3.005) D (35.05) D (56.99) E (2.793)

SO97R=SunOleic97R; 2-mepyr=2-methylpyrazine; 2,5-DMP=2,5-dimethylpyrazine; 2,3-DMP=2,3- dimethylpyrazine; 2-meox-3=2-methoxy-3-methylpyrazine; 2,3,5-TMP=2,3,5-trimethylpyrazine; Pyr=pyrazine; L-value=Hunter “L” value

* Means within a column followed by the same letter are not significantly different (Duncan’s multiple range test, 5%)

140

120

100

125/15 80 150/5 150/10 150/15 175/5 175/10

Sensory Score 60 175/15 200/5

0 FMDR Florunner Georgia Green SunOleic97R

* Lines above bars denote standard deviation **FMDR = Florida MDR 98, Georgia Green = Georgia Greene, SunOleic97R = SunOleic 97R

Figure 4-9: Least Square Means for Peanut Aroma *

140

120

100

125/15 80 150/5 150/10 150/15 175/5 175/10

Sensory Score 60 175/15 200/5

0 FMDR Florunner Georgia Green SunOleic97R

* Lines above bars denote standard deviation **FMDR = Florida MDR 98, Georgia Green = Georgia Greene, SunOleic97R = SunOleic 97R

Figure 4-10: Least Square Means for Peanut Flavor *

100

125/15 60 150/5 150/10 150/15 50 175/5 175/10

Sensory Score 175/15 40 200/5

0 FMDR Florunner Georgia Green SunOleic97R

* Lines above bars denote standard deviation **FMDR = Florida MDR 98, Georgia Green = Georgia Greene, SunOleic97R = SunOleic 97R

Figure 4-11: Least Square Means for Sweetness *

120

100

125/15 150/5 150/10 150/15 60 175/5 175/10 Sensory Score 175/15 200/5

0 FMDR Florunner Georgia Green SunOleic97R

* Lines above bars denote standard deviation **FMDR = Florida MDR 98, Georgia Green = Georgia Greene, SunOleic97R = SunOleic 97R

Figure 4-12: Least Square Means for Raw Peanut Flavor *

120

100

125/15 150/5 150/10 150/15 60 175/5 175/10

Sensory Score 175/15 200/5

0 FMDR Florunner Georgia Green SunOleic97R

* Lines above bars denote standard deviation **FMDR = Florida MDR 98, Georgia Green = Georgia Greene, SunOleic97R = SunOleic 97R

Figure 4-13: Least Square Means for Bitter Flavor *

120

100

125/15 150/5 150/10 150/15 60 175/5 175/10

Sensory Score 175/15 200/5

0 FMDR Florunner Georgia Green SunOleic97R

* Lines above bars denote standard deviation **FMDR = Florida MDR 98, Georgia Green = Georgia Greene, SunOleic97R = SunOleic 97R

Figure 4-14: Least Square Means for Crunchiness *

120

100

80 FMDR Florunner 60 Ga. Green 40 SunOleic 97R Sensory Score 20

0 51015 Roasting Time (min.)

*FMDR = Florida MDR 98, Ga. Green = Georgia Greene

Figure 4-15: Linear Effects for Peanut Aroma Attribute When Roasted at 1500C

140

120

100 FMDR 80 Florunner 60 Ga. Green SunOleic 97R

Sensory Score 40

0 51015 Roasting Time (min.)

*FMDR = Florida MDR 98, Ga. Green = Georgia Greene

Figure 4-16: Linear Effects for Peanut Aroma Attribute When Roasted at 1750C

140

120

100 FMDR 80 Florunner 60 Ga. Green SunOleic 97R

Sensory Score 40

0 51015 Roasting Time (min.)

*FMDR = Florida MDR 98, Ga. Green = Georgia Greene

Figure 4-17: Linear Effects for Peanut Flavor Attribute When Roasted at 1500C

140

120

100 FMDR 80 Florunner 60 Ga. Green SunOleic 97R

Sensory Score 40

0 51015 Roasting Time (min.)

*FMDR = Florida MDR 98, Ga. Green = Georgia Greene

Figure 4-18: Linear Effects for Peanut Flavor Attribute When Roasted at 1750C

90 80 70 60 FMDR 50 Florunner 40 Ga. Green 30 SunOleic 97R Sensory Score 20 10 0 51015 Roasting Time (min.)

*FMDR = Florida MDR 98, Ga. Green = Georgia Greene

Figure 4-19: Linear Effects for Sweetness Attribute When Roasted at 1500C

100 90 80 70 FMDR 60 Florunner 50 Ga. Green 40 SunOleic 97R 30 Sensory Score 20 10 0 51015 Roasting Time (min.)

*FMDR = Florida MDR 98, Ga. Green = Georgia Greene

Figure 4-20: Linear Effects for Sweetness Attribute When Roasted at 1750C

80.00 70.00 60.00 50.00 FMDR Florunner 40.00 Ga. Green 30.00 SunOleic 97R

Sensory Score 20.00 10.00 0.00 51015 Roasting Time (min.)

*FMDR = Florida MDR 98, Ga. Green = Georgia Greene

Figure 4-21: Linear Effects for Raw Attribute When Roasted at 1500C

40 FMDR Florunner 30 Ga. Green 20 SunOleic 97R Sensory Score 10

0 51015 Roasting Time (min.)

*FMDR = Florida MDR 98, Ga. Green = Georgia Greene

Figure 4-22: Linear Effects for Raw Attribute When Roasted at 1750C

40 FMDR Florunner 30 Ga. Green 20 SunOleic 97R Sensory Score 10

0 51015 Roasting Time (min.)

*FMDR = Florida MDR 98, Ga. Green = Georgia Greene

Figure 4-23: Linear Effects for Bitter Attribute When Roasted at 1500C

120

100

80 FMDR Florunner 60 Ga. Green 40 SunOleic 97R Sensory Score 20

0 51015 Roasting Time (min.)

*FMDR = Florida MDR 98, Ga. Green = Georgia Greene

Figure 4-24: Linear Effects for Bitter Attribute When Roasted at 1750C

100 90 80 70 FMDR 60 Florunner 50 Ga. Green 40 SunOleic 97R 30 Sensory Score 20 10 0 51015 Roasting Time (min.)

*FMDR = Florida MDR 98, Ga. Green = Georgia Greene

Figure 4-25: Linear Effects for Crunchiness Attribute When Roasted at 1500C

120

100

80 FMDR Florunner 60 Ga. Green 40 SunOleic 97R Sensory Score 20

0 51015 Roasting Time (min.)

Figure 4-26: Linear Effects for Crunchiness Attribute When Roasted at 1750C

Table 4-7: Statistical Correlations Between Pyrazines, L-value, Roasted Flavor, and Roasted Aroma for Florunner

r-squared p 2-methylpyrazine vs. L-value 0.856 0.0010 2-methylpyrazine vs. Roasted Aroma 0.485 0.0550 2-methylpyrazine vs. Roasted Flavor 0.476 0.0580 2,5-dimethylpyrazine vs. L-value 0.905 0.0005 2,5-dimethylpyrazine vs. Roasted Aroma 0.759 0.0050 2,5-dimethylpyrazine vs. Roasted Flavor 0.733 0.0070 2,3-dimethylpyrazine vs. L-value 0.849 0.0010 2,3-dimethylpyrazine vs. Roasted Aroma 0.427 0.0790 2,3-dimethylpyrazine vs. Roasted Flavor 0.447 0.0700 2,3,5-trimethylpyrazine vs. L-value 0.964 0.0003 2,3,5-trimethylpyrazine vs. Roasted Aroma 0.747 0.0060 2,3,5-trimethylpyrazine vs. Roasted Flavor 0.851 0.0050 Total pyrazines vs. L-value 0.933 0.0004 Total pyrazines vs. Roasted Aroma 0.671 0.0130 Total pyrazines vs. Roasted Flavor 0.655 0.0150 Sweetness vs. Flavor 0.756 0.0050 Roasted Aroma vs. Roasted Flavor 0.983 0.0001 L-value vs. Aroma 0.763 0.0050 L-value vs. Flavor 0.790 0.0030

Table 4-8: Statistical Correlations Between Pyrazines, L-value, Roasted Flavor, and Roasted Aroma for Florida MDR 98

r-squared p 2-methylpyrazine vs. L-value 0.916 0.0002 2-methylpyrazine vs. Roasted Aroma 0.664 0.0140 2-methylpyrazine vs. Roasted Flavor 0.707 0.0090 2,5-dimethylpyrazine vs. L-value 0.941 0.0001 2,5-dimethylpyrazine vs. Roasted Aroma 0.868 0.0010 2,5-dimethylpyrazine vs. Roasted Flavor 0.905 0.0002 2,3-dimethylpyrazine vs. L-value 0.751 0.0050 2,3-dimethylpyrazine vs. Roasted Aroma 0.651 0.0150 2,3-dimethylpyrazine vs. Roasted Flavor 0.638 0.0170 2,3,5-trimethylpyrazine vs. L-value 0.960 0.0001 2,3,5-trimethylpyrazine vs. Roasted Aroma 0.917 0.0002 2,3,5-trimethylpyrazine vs. Roasted Flavor 0.925 0.0002 Total pyrazines vs. L-value 0.951 0.0001 Total pyrazines vs. Roasted Aroma 0.807 0.0020 Total pyrazines vs. Roasted Flavor 0.847 0.0010 Sweetness vs. Flavor 0.476 0.0920 Roasted Aroma vs. Roasted Flavor 0.978 0.0001 L-value vs. Aroma 0.848 0.0010 L-value vs. Flavor 0.856 0.0010

Table 4-9: Statistical Correlations Between Pyrazines, L-value, Roasted Flavor, and Roasted Aroma for Georgia Greene

r-squared p 2-methylpyrazine vs. L-value 0.935 0.0002 2-methylpyrazine vs. Roasted Aroma 0.679 0.0120 2-methylpyrazine vs. Roasted Flavor 0.587 0.0270 2,5-dimethylpyrazine vs. L-value 0.943 0.0001 2,5-dimethylpyrazine vs. Roasted Aroma 0.792 0.0030 2,5-dimethylpyrazine vs. Roasted Flavor 0.693 0.0100 2,3-dimethylpyrazine vs. L-value 0.864 0.0010 2,3-dimethylpyrazine vs. Roasted Aroma 0.441 0.0730 2,3-dimethylpyrazine vs. Roasted Flavor 0.367 0.1110 2,3,5-trimethylpyrazine vs. L-value 0.895 0.0009 2,3,5-trimethylpyrazine vs. Roasted Aroma 0.698 0.0100 2,3,5-trimethylpyrazine vs. Roasted Flavor 0.588 0.0260 Total pyrazines vs. L-value 0.946 0.0001 Total pyrazines vs. Roasted Aroma 0.735 0.0060 Total pyrazines vs. Roasted Flavor 0.635 0.0180 Sweetness vs. Flavor 0.585 0.0270 Roasted Aroma vs. Roasted Flavor 0.978 0.0001 L-value vs. Aroma 0.660 0.0140 L-value vs. Flavor 0.555 0.0340

Table 4-10: Statistical Correlations Between Pyrazines, L-value, Roasted Flavor, and Roasted Aroma for SunOleic 97R

r-squared p 2-methylpyrazine vs. L-value 0.827 0.0020 2-methylpyrazine vs. Roasted Aroma 0.573 0.0300 2-methylpyrazine vs. Roasted Flavor 0.651 0.0150 2,5-dimethylpyrazine vs. L-value 0.871 0.0010 2,5-dimethylpyrazine vs. Roasted Aroma 0.760 0.0050 2,5-dimethylpyrazine vs. Roasted Flavor 0.853 0.0010 2,3-dimethylpyrazine vs. L-value 0.886 0.0008 2,3-dimethylpyrazine vs. Roasted Aroma 0.470 0.0610 2,3-dimethylpyrazine vs. Roasted Flavor 0.498 0.0510 2,3,5-trimethylpyrazine vs. L-value 0.805 0.0030 2,3,5-trimethylpyrazine vs. Roasted Aroma 0.751 0.0050 2,3,5-trimethylpyrazine vs. Roasted Flavor 0.810 0.0020 Total pyrazines vs. L-value 0.889 0.0007 Total pyrazines vs. Roasted Aroma 0.707 0.0090 Total pyrazines vs. Roasted Flavor 0.794 0.0030 Sweetness vs. Flavor 0.541 0.0380 Roasted Aroma vs. Roasted Flavor 0.975 0.0001 L-value vs. Aroma 0.722 0.0080 L-value vs. Flavor 0.783 0.0040

Table 4-11: Coded and Actual Prediction Equations for 2-methylpyrazine, 2,5- dimethylpyrazine, total pyrazines, L-value, Roasted Aroma, and Roasted Flavor for Florunner

2-methypyrazine coded 7.01 + 8.21 time + 23.67 temp. + 20.72 temp.^2 + 24.87 time X temp. + 12.59 time X temp.^2 R-square: 0.8678 actual 19.77 + 27.38 time + 0.34 temp. – 0.0032 temp.^2 – 0.45 time X temp. + 0.0018 time X temp.^2 2,5-dimethylpyrazine coded 19.42 + 16.37 time + 23.96 temp. + 12.44 time X temp. R-square: 0.8875 actual -9.33 – 7.51 time – 0.024 temp. + 0.066 time X temp. All Pyrazines coded 33.11 + 29.86 time + 44.32 temp. + 24.78 time X temp. R-square: 0.8547 actual -3.88 – 15.51 time – 0.14 temp. + 0.132 time X temp. Hunter L-value coded 57.79 – 5.90 time – 15.95 temp. – 3.78 temp.^2 – 6.84 time X temp. + 6.24 temp.^3 R-square: 0.9309 actual 99.33 + 4.75 time + 10.19 temp. – 0.06 temp.^2 – 0.04 time X temp. + 0.0001 temp.^3 Roasted Aroma coded 93.56 + 23.17 time + 50.53 temp. – 21.65 temp.^2 R-square: 0.8077 actual -578.23 + 4.63 time + 6.35 temp. – 0.015 temp.^2 Roasted Flavor coded 87.16 + 24.51 time + 56.15 temp. R-square: 0.7885 actual -205.17 + 4.90 time + 1.50 temp.

Table 4-12: Coded and Actual Prediction Equations for 2-methylpyrazine, 2,5- dimethylpyrazine, total pyrazines, L-value, Roasted Aroma, and Roasted Flavor for Florida MDR 98

2-methypyrazine coded 10.11 + 11.13 time + 22.02 temp. + 19.88 temp.^2 + 23.17 time X temp. R-square: 0.8649 Actual 466.53 – 17.85 time – 5.24 temp. + 0.014 temp.^2 + 0.12 time X temp. 2,5-dimethylpyrazine coded 24.62 + 13.30 time + 34.67 temp. – 7.82 time^2 + 17.94 temp.^2 + 18.10 time X temp. R-square: 0.8777 Actual 310.24 – 6.77 time – 4.19 temp. – 0.31 time^2 + 0.01 temp.^2 + 0.24 time X temp. All Pyrazines coded 32.86 + 26.66 time + 62.16 temp. + temp^2 + 44.61 time X temp. R-square: 0.8879 Actual 820.52 – 33.30 time – 9.62 temp. + 0.03 temp.^2 + 0.24 time X temp. Hunter L-value coded 59.64 – 5.68 time – 14.29 temp. – 8.40 temp.^2 – 8.48 time X temp. R-square: 0.7946 Actual -98.28 + 6.22 time + 2.01 temp. – 5.97 temp^2 – 0.05 time X temp. Roasted Aroma coded 80.26 + 19.66 time + 60.13 temp. R-square: 0.9789 Actual -219.62 + 3.93 time + 1.60 temp. Roasted Flavor coded 79.33 + 23.83 time + 66.62 temp. R-square: 0.9801 Actual -257.01 + 4.77 time + 1.77 temp.

Table 4-13: Coded and Actual Prediction Equations for 2-methylpyrazine, 2,5- dimethylpyrazine, total pyrazines, L-value, Roasted Aroma, and Roasted Flavor for Georgia Greene

2-methypyrazine coded 4.93 + 7.02 time + 13.53 temp. + 2.81 time^2 + 8.50 temp.^2 + 11.31 time X temp. R-square: 0.7965 Actual 201.09 – 10.64 time – 2.20 temp. + 0.11 time^2 + 6.04 temp.^2 + 0.06 time X temp. 2,5-dimethylpyrazine coded 13.24 + 9.00 time + 18.78 temp + 5.93 time X temp. R-square: 0.8945 Actual -34.75 – 3.33 time + 0.18 temp. + 0.03 time X temp. All Pyrazines coded 18.45 + 17.11 time + 34.95 temp. + 3.76 time^2 + 15.38 temp.^2 + 22.42 time X temp. R-square: 0.8413 Actual 330.91 – 19.01 time – 3.81 temp. + 0.15 time^2 + 0.01 temp.^2 + 0.12 time X temp. Hunter L-value coded 57.50 – 5.14 time – 9.76 temp – 5.39 time X temp. R-square: 0.7842 Actual 63.35 + 3.64 time + 0.03 temp. – 0.03 time X temp. Roasted Aroma coded 88.28 + 23.56 time + 57.36 temp. + 20.36 time X temp. R-square: 0.9165 Actual -30.98 – 12.93 time + 0.44 temp. – 0.03 time X temp. Roasted Flavor coded 85.17 + 24.21 time + 53.47 temp. + 18.49 time X temp. R-square: 0.9259 Actual -34.74 – 11.18 time + 0.44 temp. + 0.10 time X temp.

Table 4-14: Coded and Actual Prediction Equations for 2-methylpyrazine, 2,5- dimethylpyrazine, total pyrazines, L-value, Roasted Aroma, and Roasted Flavor for SunOleic 97R

2-methypyrazine coded 3.12 + 8.14 time + 14.26 temp. + 2.39 time^2 + 18.42 temp.^2 + 19.00 time X temp. R-square: 0.9002 Actual 445.16 – 16.75 time – 4.89 temp. + 0.09 time^2 + 0.01 temp.^2 + 0.10 time X temp. 2,5-dimethylpyrazine coded 9.37 + 9.26 time + 21.30 temp. – 1.02 time^2 + 20.19 temp.^2 + 17.44 time X temp. R-square: 0.9547 Actual 424.74 – 12.44 time – 5.02 temp. – 0.04 time^2 + 0.01 temp.^2 + 0.09 time X temp. All Pyrazines coded 15.33 + 18.90 time + 38.85 temp. – 0.028 time^2 + 41.20 temp.^2 + 38.98 time X temp. R-square: 0.8988 Actual 920.45 – 29.97 time – 10.56 temp. – 0.0011 time^2 + 0.029 temp.^2 + 0.21 time X temp. Hunter L-value coded 57.12 – 4.84 time – 9.40 temp. + 2.05 time^2 – 8.51 temp.^2 – 9.87 time X temp. R-square: 0.7961 Actual -129.54 + 5.94 time + 2.24 temp. + 0.081 time^2 – 0.006 temp.^2 – 0.05 time X temp. Roasted Aroma coded 71.66 + 30.56 time + 66.06 temp. R-square: 0.9631 Actual -275.69 + 6.11 time + 1.76 temp. Roasted Flavor coded 69.83 + 27.32 time + 65.03 temp. R-square: 0.9640 Actual -266.61 + 5.46 time + 1.73 temp.

CHAPTER 5 FATTY ACID CONTENT, MOISTURE, AND SENSORY EVALUATION OF STORED ROASTED PEANUT GENOTYPES FROM VARIOUS PLANTING DATES

Introduction

In recent years, there has been a major interest in foods with a high oleic acid content, due to health benefits associated by mimicking a diet similar to cultures found near the Mediterranean Sea. The peanut breeding program at the University of Florida developed a germplasm having a higher oleic acid content (~81% oleic acid) than olive and canola oils (Gorbet and Knauft et al., 1997). In a study with postmenopausal women as the test group, a positive correlation between the decrease of LDL/HDL cholesterol ratios and high oleic peanut consumption was observed (O’Byrne et al., 1995). SunOleic

95R was meant to be the first in line of “heart healthy” peanuts, but due to Tomato

Spotted Wilt Virus (TSWV) susceptibility, SunOleic 95R was not fully accepted by peanut growers (Peanut Farmer, 1996). The Tomato Spotted Wilt Virus is a ring spot disease first described by Costa in Brazilian peanuts in 1941 (Porter et al., 1982). Small insects known as thrips are thought to be the causative agent of TSWV transfer from plant to plant. The high oleic peanut released in 1997, the SunOleic 97R, was less susceptible to TSWV than its predecessor, SunOleic 95R, but still inferior to other

“normal” oleic genotypes. TSWV is a major problem for growing peanuts in the

Southeastern United States. In 1995-1997, TSWV was the cause of $30 to $40 million dollars in losses to the peanut industry in Georgia alone (Mullen, 2001). There are many ways to combat TSWV, but peanut breeders are still searching for a peanut with disease

93 94 resistance, greater yield, good potential roast flavor, longer shelf life, and increased health benefits.

The maturity of the seed at harvest, regardless of size, plays an important role in the composition, sensory profile and oxidative stability of roasted peanuts (McNeill and

Sanders et al., 1998; Pattee et al., 1998; Wheeler et al., 1994; Sanders et al., 1989a).

Genotype and seed maturity have been shown to influence fatty acid profiles (Hinds,

1995). When peanuts are planted late in the season, cooler temperatures are encountered as they reach maturity. Peanuts planted early have been shown to have greater yield and tend to be graded higher due to soil moisture levels and temperatures that are more conducive to growth and germination (Mozingo et al., 1991). Cooler air and soil conditions encountered during early planting may account for the decrease in oleic / linoleic acid ratio in late maturity peanut genotypes (McNeill and Sanders et al., 1998).

Immature peanuts have also been found to have decreased oxidative stability during storage (McNeill and Sanders et al., 1998). Peanut genotypes having different oleic / linoleic acid ratios have not been tested against one another after roasting and storage.

Relative changes measured in differing genotypes planted and harvested at different dates allow investigators to further predict flavor potential in peanuts.

Sensory quality is affected by environmental factors, maturity, and genotype.

More mature seeds have greater potential for full roasted peanut flavor (Sanders et al.,

1989a). Immature peanuts have the propensity to form a fruity-fermented off-flavor and are unable to reach the roasted peanut flavor levels of a more mature peanut (Sanders et al., 1989b). Variations in peanut flavor as a function of genotype have been reported for

a variety of attributes, including roast peanut, sweet, bitter, cardboardy, and painty

flavors (O’Keefe et al., 1995; Pattee et al., 1998; Pattee and Giesbrecht, 1990).

The objective of this research was to note the changes in sensory flavor as a function

of planting and harvest dates, as well as establishing the changes in fatty acid profile and

oxidative stability of known and experimental genotypes of peanuts that have various oil

chemistries and maturities.

Materials and Methods

Sample Preparation and Storage

Seed from ten peanut genotypes were used as the test seeds: Florida MDR 98 (a

mid-oleic variety); Georgia Greene, Florunner, and Andru 93 (normal-oleic genotypes);

SunOleic 97R (a high-oleic variety); and five experimental lines (varying oleic acid

content). Florida MDR 98, Georgia Greene, and SunOleic 97R were planted on early

(4/15/98), normal (5/13/98), and late (6/10/98) planting dates. Andru 93, Florunner, and

the five breeding lines included in the experiment were planted on 5/13/98. Peanut yield,

shelling, and grading were done at the University of Florida North Florida Research and

Education Center at Marianna, Florida. The peanuts were sent to the University of

Florida, Gainesville, for further analysis. Prior to roasting, the shelled peanuts were

bags, and stored at –200C for 23 days.

The peanuts were roasted at 1750C in a standard laboratory oven until Hunter “L”

color values of 50-52 were achieved (Sanders et al., 1989a). After roasting, the peanuts

freezer bags, and stored for up to three days at –200C and until all peanuts were roasted.

Descriptive sensory panels were conducted as soon as possible after roasting, with no

more than seven days of frozen storage. After the peanuts equilibrated to room

temperature, they were transferred to dessicators above a saturated salt solution of

potassium carbonate having an aw of 0.44 for six months of storage at ambient temperature (~250C). The saturated salts were maintained weekly as to ensure saturation

and monitored using a relative humidity meter (Fisher Scientific, Pittsburgh, PA).

Sensory Analysis

A trained sensory panel evaluated the peanuts at 0, 3, and 6 months of storage

after roasting. Fourteen trained panelists (8 male, 6 female) consisting of students and

staff of the Food Science Department who had previous experience on peanut sensory

panels were used throughout the course of the study. The panelists were trained in three

thirty-minute sessions in the University of Florida Food Science and Human Nutrition

Department Taste Panel Room before the beginning of the study. The sensory attributes

tested were roast peanut flavor, sweetness, cardboardy, and painty. Roasted peanut flavor

intensity was measured using varying levels of roast, denoted by color measurements, as

described by Sanders et al. (1989a). Sweetness, cardboardy and painty intensities were

described to the panelists and examples were given to iterate attribute levels in

accordance to Johnsen et al. (1989). During training, panelists were provided with

samples of freshly roasted and stored peanuts that had been stored to result in several

levels of oxidation (Braddock et al., 1995; Mugendi et al., 1998). Once the panelists

were familiar with the attributes to be analyzed in the study, they were asked to rate fresh

roasted and various stored roasted peanuts of differing genotypes and storage times.

Tests and training were conducted until all members of the panel were consistent when

given blind samples to rate on a line scale. All attributes were rated on a 150-millimeter

line scale, where the far left end of the scale (0 mm) was denoted as none and the far

right, high (150 mm). At each testing session, reference samples of fresh roasted peanuts

were given as a control for the panelists (a fresh roasted Runner type peanut sample

stored in glass jars flushed with nitrogen and stored at –20oC). All stored peanuts were equilibrated to room temperature before sensory evaluation. Panelists were given approximately three grams of peanuts per sample. Genotypes SunOleic 97R, Florida

MDR 98, and Georgia Greene were presented together by each planting date, in duplicate, for three sensory panels (4/15/98, 5/13/98, and 6/10/98). Panels for single planting date genotypes Andru 93, Florunner, 90XOL61-HO2-1-1-b2-B, 86x13A-4-2-3-

2-b3-B, 90X7-1-5-1-b2-B, 89xOL28-HO1-7-4-1-2-b2-B, and 88X1B-OLBC-6-1-3-1-b2-

B, in duplicate, for two sensory panels (Andru 93, Florunner, 90XOL61-HO2-1-1-b2-B,

and 86x13A-4-2-3-2-b3-B; 90X7-1-5-1-b2-B, 89xOL28-HO1-7-4-1-2-b2-B, and 88X1B-

OLBC-6-1-3-1-b2-B . Sample order and sample coding were picked at random for each

panel. Panelists were presented with water and unsalted crackers at each taste session for

palate rinsing. The panelists were required to take a ten-minute break between duplicate

samples, and were given a different order of presentation to maintain blind sampling. An

example of the ballot used can be found in Appendix C.

Moisture

The moisture of the stored peanuts was tested using the AOAC Official Method

925.40 Moisture in Nuts and Nut Products (AOAC, 1990).

Roast Color

A BYK-Gardner Colorguard (Columbia, MD) colorimeter was used for all measurements. The colorimeter was calibrated with black and white tiles before testing and allowed to warm up for 30 minutes before measurements were taken. Approximately

15 grams of peanuts were added to a round plastic optical cup (5 cm diameter, 4 cm high) and covered with an aluminum foil lined lid, both provided by BYK-Gardner. All peanuts were roasted to a Hunter L-value of 50-51 (Sanders et al., 1989a).

Fatty Acids

Peanut oil was extracted and the corresponding fatty acids were separated, identified and quantified at the University of Florida’s laboratory at the NFREC at

Quincy, FL, (Andersen and Gorbet, 2001). Peanut lipids were extracted by a modified

Folch extraction (Christie, 1982). After extraction, the samples were immediately flushed with nitrogen. Additional dichloromethane was added to bring the volume to 2 mL. Methylation was accomplished by adding 100 µL of dichloromethane/lipid solution to 25 µL MethPrep II (Alltech Associates, Inc., Deerfield, IL) in an autosampler vial.

Nitrogen gas was added to the vials and were capped and left undisturbed for 30 minutes

(Andersen and Gorbet, 2002).

A Hewlett Packard 6890 gas chromatograph (Wilmington, DE) fitted with an HP flame ionization detector and an HP-225 column (l, 30m; i.d., 320µm) was used to profile the peanut lipid methyl esters to their corresponding fatty acids. Gas flow rates per minute were 30, 30, and 300 mL per minute for hydrogen, nitrogen, and air, respectively.

Helium was used as the carrier gas. One µL injections were split 100:1 in a 2200C injector. Temperature was ramped at 50C per minute from 1900C to 2200C. All samples

99 were run in duplicate. All ten genotypes were available for fatty acid analysis at the three planting dates (4/15/98 (1),5/13/98 (2), 6/10/98 (3)) (Andersen and Gorbet, 2002).

Statistics

A randomized complete block design was used (Rao, 1998) and the data was analyzed by analysis of variance (ANOVA) using SAS (Cary, NC) for both multiple and single planting date genotypes, separately. The statistical model in SAS was defined as

(sensory attribute = rep panelist | storage | genotype | planting date) for multiple planting date genotypes, and (sensory attribute = rep panelist | storage | genotype) for single planting date genotypes. Means were separated using a Duncan’s Mean Separation test when a significant F-value was obtained. Response surface plots were constructed using

Statistica for windows (version 4.5, Statsoft, Tulsa OK).

Results and Discussion

Sensory Analysis

Multiple planting date genotypes (main effects) (Table 5-1) (SunOleic 97R, Georgia Greene, Florida MDR98)

Roast peanut flavor showed significant decreases during storage, while cardboardy and painty off-flavors increased significantly (Table 5-1). Main effects of planting date showed no significant differences for any of the attributes. SunOleic 97R had significantly higher roast peanut flavor than Florida MDR 98 and Georgia Greene.

This is possibly due to SunOleic 97’s propensity to be roasted longer to achieve roasted peanut flavor. It would appear that flavor is not as readily formed in SunOleic 97R, given the same roasting parameters. Several more minutes (5-10) of roasting was required for SunOleic 97R to reach a Hunter L color value of 50-51 in comparison

;lkj;lkj;lk

100

to Florida MDR 98 and Florunner. All genotypes had different sweetness levels,

Georgia Greene being the highest and SunOleic 97R, the lowest.

Interactions between factors, such as planting date and variety, mark the failure of one factor to produce the same effect on a response, such as attribute, at differing levels of another factor (Montgomery, 1999). If a significant interaction is achieved, significance of the corresponding factors concludes their role in the interaction. For example, in the case of roast peanut flavor at time 0 (Table 5-2), there was a significant planting date by variety interaction. Under the interaction, variety was significant and planting date was not. Since variety, as well as planting date by variety, was significant, variety then becomes a non-factor in the interaction, due to its common sharing of significance with the planting date by variety interaction. Therefore, since planting date was not significant, one (or all) of the planting dates did not produce the same peanut flavor for the different genotypes.

As mentioned in the previous example, significant interaction between planting date and variety was apparent throughout storage for roasted peanut flavor (Tables 5-2 to

5-4). Planting date, variety, and their interaction were significant at 6 months of storage.

When all levels under a significant interaction are observed, it is assumed all tests are conclusive, meaning that at 6 months of storage, roasted peanut flavor was significantly influenced by both planting date and variety. Sweetness planting dates by variety interactions were not observed until 6 months of storage, where planting dates did not produce the same sweetness for the different genotypes. After 3 months of storage, the cardboardy sensory attribute denoted a significant planting date by variety interaction and carried over to 6 months of storage. Since neither planting date nor variety were

101 significant at 3 or 6 months of storage, planting dates and genotypes both played a non- significant role in the interaction. This also holds true for painty sensory ratings after 3 months of storage.

Single planting date genotypes (main effects) (Table 5-5) (Andru 93, Florunner, 90XOL61-HO2-1-1b2-B, 86x13A-4-2-3-2-b3-B, 90X7-1-5-1-b2-B, 89xOL28-HO1-7-4- 1-2-b2-B, and 88X1B-OLBC-6-1-3-1-b2-B )

Roast peanut flavor decreased significantly every three months of storage for all genotypes tested. There were no significant changes in sweetness, cardboardy, or painty sensory attributes during storage. Sweetness decreased during storage, but not to significant levels at an alpha of 0.05. Cardboardy and painty off flavors increased slightly during storage, however not significantly. Decreases in roast peanut flavor may be due to flavor fade or masking of peanut flavor by aldehydes in peanuts stored over long storage times (Dimick, 1994; O’Keefe et al., 1995; Mate et al., 1996).

Experimental line 86x13A-4-2-3-2-b2-B showed the highest roast peanut flavor, the lowest sweetness, the highest cardboardy and the highest painty flavors at all storage times. Roast peanut flavor in Andru93, Florunner, and 88X1B-OLBC1-6-1-3-1-b2-B did not significantly differ from one another during storage. None of the single date planting genotypes had significantly differing levels of painty flavor after 6 months of storage.

Single planting date genotypes (5-6-98) showed significant storage by variety interactions in roast peanut flavor and sweetness, indicating that storage has an effect on variety for roast flavor and sweetness levels. There were no significant interactions for painty and cardboardy off-flavors.

Changes in cardboardy, painty, and roasted peanut flavor are typical throughout peanut storage. Cardboardy and painty off-flavors are formed as a product of

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Changes in cardboardy, painty, and roasted peanut flavor are typical throughout peanut storage. Cardboardy and painty off-flavors are formed as a product of autooxidation by the formation of specific aldehydes during storage at ambient temperatures (O’Keefe et al., 1995). The cardboardy attribute (2t,6t-nonadienal) tends to only be found in higher levels in peanuts with a higher than normal oleic acid chemistry, never fully reaching the painty attribute (pent-2-enal) that is normally associated with

highly oxidized lipids. Roasted peanut flavor fades during storage, especially over long

periods of time, for a various reasons, including the propensity for peanuts to pick up

water, thus diluting the flavor in a peanut matrix (Dimick, 1994; Mate et al., 1996;

O’Keefe et al., 1995). Sweetness declined as roasted peanut flavor increased, in the

majority of the roasted seed tested.

Moisture

Moisture content increased during storage at an aw of 0.44 for all genotypes,

increasing from 1.6% immediately after roasting to nearly 7% after six months of storage.

Previous research has suggested that this change may be associated to a breakdown in

cellular compartmentalization, due to the significant decrease in phospholipids when

peanuts were stored over a 2-year period at roughly 9% moisture (Pattee et al., 1981).

Fatty Acid Analysis

There were no significant differences in fatty acid percentage for most of the fatty acid methyl esters tested as a function of planting date (Table 5-9). There were differences in planting date for linoleic acid content for Florida MDR 98, SunOleic 97R, and 92XOL61-HO2-1-1-b2-B (Table 5-6 and Figures 5-1 and 5-2). All planting dates had significantly different levels of linoleic acid for Florida MDR 98. The highest level

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of linoleic acid in Florida MDR 98 peanut seed was planted on 6/10/98, followed by

4/15/98, and the lowest levels found at the 5/13/98 planting date. This agrees with temperature effects previously reported in the literature (Andersen and Gorbet, 2002)

SunOleic 97R peanut seed showed significantly lower levels of linoleic acid at the

4/15/98 planting date compared to the other planting dates. The 5/13/98 planting date showed the lowest levels of linoleic acid for the 89xOL28-HO1-7-4-1-2-b2-B line and was significantly different from the other planting dates.

The oleic to linoleic acid ratio shows greater differences between planting dates

(Table 5-8 and Figure 5-2) when compared to single fatty acids. The largest changes in oleic/linoleic acid ratio were found in the 89xOL28-HO1-7-4-1-2-b2-B peanut, followed by SunOleic 97R, 88x1B-OLBC1-6-1-3-1-b2-B, 90xOL61-HO2-1-1-b2-B, Florida MDR

98, 90x7-1-5-1-b2-B, Andru 93, 86x13A-4-2-3-2-b3-B, Georgia Greene, and Florunner, respectively (Table 5-8). The 5/13/98 planting date, which previously showed the lowest linoleic acid content for the planting dates tested, had an oleic/linoleic ratio of 50.8. This would suggest that the 89xOL28-HO1-7-4-1-2-b2-B seeds planted during 5/13/98 would be the most shelf stable, healthy peanuts found in this study by a significant margin.

SunOleic 97R, previously shown to be the most stable, healthy peanut currently available, only elicited a oleic to linoleic acid ratio of 30.7. Table 5-8 and Figure 5-1 show other experimental lines having higher or equal oleic acid content to that of the

SunOleic 97R peanut. 90xOL61-HO2-1-1-b2-B showed levels ranging from 28.9-34.2 and 88x1B-OLBC1-6-1-3-1-b2 ranged from 40.7 to 47.2. Further research on the disease resistance, yield, flavor, as well as other charcateristics of the experimental genotypes

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89xOL28-HO1-7-4-1-2-b2-B, 88x1B-OLBC1-6-1-3-1-b2, and 90xOL61-HO2-1-1-b2-B is currently in progress.

The oleic/linoleic acid ratios did not agree with studies done by McNeill and

Sanders (1998), which stated that the oleic/linoleic acid ratio decreased in immature peanuts, thus decreasing oxidative stability. Oleic/linoleic acid ratios may not be the best way to characterize the oil chemistry when dealing with high-oleic seed. This is due to the significant change in the oleic/linoleic acid ratio when linoleic acid changes are relatively small. The incorporation of an early planting date to the study shows similar results to the late planting date in regards to lower oleic/linoleic acid ratios, and may explain the differences between studies. It should be noted that environmental conditions change from year to year, therefore a one-year study such as this does not have the power of multiple year studies that are ongoing. Andersen and Gorbet (2002) have published studies incorporating this data, focusing primarily on the oil chemistry.

Increased oleic acid peanuts have been studied since the 1980’s, and may be vital to the peanut industry based on high monounsaturated fat products that have longer shelf lives with greater oxidative stability. This could also play a role in the peanut’s already

“heart healthy” nature. Depending on disease resistance, especially with tomato spotted wilt virus, these peanuts should find their way to consumers in the near future.

Conclusions

Roast peanut flavor declines during storage regardless of variety. Planting date did not appear to effect roasted peanut flavor, sweetness, painty, or cardboardy sensory scores, with the exception of the 4/15/98 planting date. Sweetness declined as roast peanut flavor increased, regardless of genotype or planting date in the majority of the

105 roasted seed tested. Recommended planting dates, such as 5/6/98, may be the best time to plant peanuts, as a function of sensory potential, as the highest sensory scores for roast peanut flavor were noted at that date. SunOleic 97R had the highest roasted peanut scores and the lowest levels of oxidation over 6 months of storage.

Fatty acid profile did not significantly change as a function of planting date.

Several of the experimental genotypes, 92xOL103-1-2-1-b2-B, 90xOL61-HO2-1-1-b2-B, and 88x1B-OLBC1-6-1-3-1-b2-B showed similar oleic acid content to SunOleic 97R, labeling them as high-oleic peanuts.

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Table 5-1: Main Effects of Storage Time, Planting Date and Genotype on Sensory Characteristics *

Storage Time Roast Peanut Sweetness Cardboardy Painty 0 months (81.64) A (55.25) A (12.14) A (10.24) A 3 months (70.69) B (51.92) A (19.57) B (15.34) B 6 months (57.94) C (44.94) A (27.32) C (22.64) C

Planting Date Roast Peanut Sweetness Cardboardy Painty 4/15/98 (67.40) A (49.79) A (20.92) A (17.33) A 5/6/98 (73.18) A (50.11) A (18.54) A (15.42) A 5/27/98 (69.68) A (52.20) A (19.57) A (15.47) A

Variety Roast Peanut Sweetness Cardboardy Painty SunOleic 97R (80.35) A (48.23) A (19.49) A (14.68) A Florida MDR 98 (64.77) B (52.95) B (19.10) A (15.98) A Georgia Greene (65.15) B (50.93) C (20.44) A (17.56) A

Planting Dates – 4/15/98, 5/6/98, and 5/27/98 Genotypes – SunOleic 97R, Florida MDR 98, Georgia Greene

* Means within a column followed by the same letter are not significantly different (Duncan’s multiple range test, 5%)

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Table 5-2: ANOVA Interactions for Multiple Planting Dates at Time 0

Roast Peanut source error term MS F p-value planting date panelist*planting date 131.204 0.46 0.6347 variety panelist*variety 6735.493 15.74 0.0001 planting date*variety panelist*planting date*variety 9547.981 26.70 0.0001

Sweetness source error term MS F p-value planting date panelist*planting date 71.604 0.19 0.8308 variety panelist*variety 179.615 0.95 0.3992 planting date*variety panelist*planting date*variety 201.759 1.62 0.1809

Cardboardy source error term MS F p-value planting date panelist*planting date 56.959 0.33 0.7226 variety panelist*variety 31.515 0.46 0.6366 planting date*variety panelist*planting date*variety 135.676 1.43 0.2362

Painty source error term MS F p-value planting date panelist*planting date 14.744 0.05 0.9519 variety panelist*variety 186.411 1.91 0.1669 planting date*variety panelist*planting date*variety 218.822 1.26 0.2963

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Table 5-3: ANOVA Interactions for Multiple Planting Dates at 3 Months of Storage

Roast Peanut source error term MS F p-value planting date panelist*planting date 1389.448 1.74 0.1942 variety panelist*variety 16367.026 39.95 0.0001 planting date*variety panelist*planting date*variety 17269.115 34.31 0.0001

Sweetness source error term MS F p-value planting date panelist*planting date 374.670 0.83 0.4463 variety panelist*variety 1165.848 6.63 0.0044 planting date*variety panelist*planting date*variety 337.859 2.34 0.0659

Cardboardy source error term MS F p-value planting date panelist*planting date 627.215 1.30 0.2877 variety panelist*variety 273.693 1.81 0.1827 planting date*variety panelist*planting date*variety 1087.776 4.39 0.0037

Painty source error term MS F p-value planting date panelist*planting date 322.270 0.39 0.6792 variety panelist*variety 806.470 2.29 0.1195 planting date*variety panelist*planting date*variety 1248.359 4.86 0.0020

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Table 5-4: ANOVA Interactions for Multiple Planting Dates at 6 Months of Storage

Roast Peanut source error term MS F p-value planting date panelist*planting date 2486.381 3.23 0.0548 variety panelist*variety 2744.559 11.38 0.0002 planting date*variety panelist*planting date*variety 2747.170 7.60 0.0001

Sweetness source error term MS F p-value planting date panelist*planting date 297.070 0.62 0.5427 variety panelist*variety 460.626 8.04 0.0001 planting date*variety panelist*planting date*variety 865.715 9.85 0.0001

Cardboardy source error term MS F p-value planting date panelist*planting date 284.270 0.63 0.5410 variety panelist*variety 206.048 1.62 0.2159 planting date*variety panelist*planting date*variety 609.576 3.59 0.0113

Painty source error term MS F p-value planting date panelist*planting date 231.659 1.28 0.2946 variety panelist*variety 122.726 0.77 0.4715 planting date*variety panelist*planting date*variety 280.581 0.95 0.4400

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Table 5-5: Main Effects of Storage Time and Variety on Sensory *

Storage Time Roast Peanut Sweetness Cardboardy Painty 0 months (83.657) A (55.595) A (15.843) A (12.005) A 3 months (76.505) B (53.381) A (20.586) A (15.805) A 6 months (61.557) C (47.676) A (22.276) A (18.448) A

Variety Roast Sweetness Cardboardy Painty Peanut Andru 93 (73.68) C (49.80) CD (20.31) ABC (16.49) A Florunner (69.47) C (53.96) AB (19.50) BC (16.71) A 90XOL61-HO2-1-1b2-B (78.70) B (56.83) A (15.77) D (10.89) A 86x13A-4-2-3-2-b3-B (84.44) A (47.20) D (22.80) A (17.94) A 90X7-1-5-1-b2-B (78.69) B (51.76) BC (22.19) AB (16.02) A 89xOL28-HO1-7-4-1-2-b2-B (59.61) D (52.97) BC (18.18) CD (16.93) A 88X1B-OLBC1-6-1-3-1-b2-B (72.76) C (53.01) BC (18.23) CD (12.94) A

Genotypes – (1) Andru 93, (2) Florunner, (3) 90XOL61-HO2-1-1b2-B, (4) 86x13A-4-2- 3-2-b3-B, (5) 90X7-1-5-1-b2-B, (6) 89xOL28-HO1-7-4-1-2-b2-B, (7) 88X1B- OLBC1-6-1-3-1-b2-B

* Means within a column followed by the same letter are not significantly different (Duncan’s multiple range test, 5%)

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Table 5-6: ANOVA Interactions for Single Planting Date Genotypes

Roast Peanut source error term MS F p-value storage panelist*storage 26704.9 6.23 0.0058 variety panelist*variety 5735.16 14.59 0.0001 storage*variety panelist*storage*variety 800.010 2.06 0.0219

Sweetness source error term MS F p-value storage panelist*storage 3505.55 1.28 0.2940 variety panelist*variety 851.262 4.11 0.0011 storage*variety panelist*storage*variety 332.247 1.91 0.0367

Cardboardy source error term MS F p-value storage panelist*storage 2335.91 1.82 0.1801 variety panelist*variety 540.539 2.33 0.0394 storage*variety panelist*storage*variety 229.871 1.05 0.4088

Painty source error term MS F p-value storage panelist*storage 2202.72 2.08 0.1444 variety panelist*variety 577.417 2.03 0.0699 storage*variety panelist*storage*variety 215.829 0.97 0.4843

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Fatty Acid Profile

Table 5-7: Fatty Acid Percentage for Various Genotypes of Multiple Planting Dates

Florida MDR 98 Palmitic Stearic Oleic Linoleic Arachidonic Eicosenoic Behenic Lignoceric 04/15/98 8.7 3.1 63.4 17.1 1.6 1.2 3.5 1.5 05/13/98 8.1 3.5 65.8 14.6 1.7 1.2 3.5 1.5 06/10/98 8.8 3.2 59.8 20.3 1.5 1.3 3.6 1.5 Georgia Greene Palmitic Stearic Oleic Linoleic Arachidonic Eicosenoic Behenic Lignoceric 04/15/98 10.0 2.6 53.0 27.4 1.3 1.2 2.9 1.5 05/13/98 10.3 2.6 50.2 29.5 1.3 1.3 3.2 1.6 06/10/98 9.9 2.5 52.4 28.0 1.3 1.3 3.1 1.6 Sun Oleic 97R Palmitic Stearic Oleic Linoleic Arachidonic Eicosenoic Behenic Lignoceric 04/15/98 5.8 2.2 81.5 2.7 1.2 2.0 2.7 1.8 05/13/98 6.2 2.7 79.1 4.5 1.2 1.8 2.8 1.7 06/10/98 5.9 2.7 79.5 4.2 1.3 1.9 2.8 1.8 Andru 93 Palmitic Stearic Oleic Linoleic Arachidonic Eicosenoic Behenic Lignoceric 04/15/98 10.2 2.4 54.3 26.4 1.2 1.3 2.7 1.5 05/13/98 10.0 2.5 55.1 25.3 1.3 1.4 3.0 1.6 06/10/98 10.2 2.4 53.4 27.0 1.2 1.4 2.9 1.6 86x13A-4-2-3-2-b3-B Palmitic Stearic Oleic Linoleic Arachidonic Eicosenoic Behenic Lignoceric 04/15/98 8.7 2.6 59.0 22.9 1.3 1.3 2.8 1.4 05/13/98 8.6 2.9 59.0 22.8 1.3 1.3 2.8 1.3 06/10/98 8.8 2.8 57.8 24.1 1.3 1.3 2.7 1.3 89xOL28-HO1-7-4-1-2-b2-B Palmitic Stearic Oleic Linoleic Arachidonic Eicosenoic Behenic Lignoceric 04/15/98 6.1 3.9 78.5 3.5 1.6 1.6 3.4 1.5 05/13/98 5.8 3.5 80.9 1.6 1.5 1.7 3.5 1.6 06/10/98 5.9 3.3 79.7 3.2 1.5 1.7 3.3 1.5 90xOL61-HO2-1-1-b2-B Palmitic Stearic Oleic Linoleic Arachidonic Eicosenoic Behenic Lignoceric 04/15/98 5.6 2.6 82.5 2.4 1.2 1.7 2.5 1.5 05/13/98 5.8 2.5 82.0 2.7 1.2 1.7 2.7 1.5 06/10/98 5.7 2.4 81.8 2.8 1.2 1.8 2.7 1.5 88x1B-OLBC1-6-1-3-1-b2 Palmitic Stearic Oleic Linoleic Arachidonic Eicosenoic Behenic Lignoceric 04/15/98 6.2 3.8 80.8 1.7 1.6 1.5 3.0 1.5 05/13/98 6.4 3.4 80.4 2.1 1.6 1.6 3.1 1.5 06/10/98 6.3 3.3 80.9 1.8 1.6 1.6 3.1 1.5 90x7-1-5-1-b2-B Palmitic Stearic Oleic Linoleic Arachidonic Eicosenoic Behenic Lignoceric 04/15/98 9.7 2.4 56.3 24.2 1.3 1.4 3.0 1.7 05/13/98 10.0 2.5 54.8 25.4 1.3 1.3 3.1 1.6 06/10/98 9.9 2.4 53.8 26.3 1.3 1.4 3.2 1.7 Florunner Palmitic Stearic Oleic Linoleic Arachidonic Eicosenoic Behenic Lignoceric 04/15/98 10.1 2.7 52.8 27.5 1.3 1.2 2.8 1.6 05/13/98 10.3 2.6 51.3 28.6 1.3 1.3 3.0 1.6 06/10/98 10.2 2.7 51.6 28.5 1.3 1.3 2.9 1.6 * data provided by Andersen and Gorbet (2002)

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Table 5-8: Oleic/Linoleic Acid Ratio, Iodine Value, and Percent Saturation of Multiple Planting Date Genotypes

18:1/18:2 IV %Saturation Florida MDR 98 15-Apr 3.7 85.1 18.3 13-May 4.3 83.6 18.3 10-Jun 3.0 87.6 18.6 Georgia Greene 15-Apr 1.9 94.1 18.3 13-May 1.7 95.4 19.0 10-Jun 1.9 94.5 18.4 Sun Oleic 97R 15-Apr 30.7 76.4 13.8 13-May 18.1 77.2 14.6 10-Jun 21.9 77.0 14.4 Andru 93 15-Apr 2.1 93.4 18.3 13-May 2.2 92.2 18.3 10-Jun 2.0 93.7 18.3 86x13A-4-2-3-2-b3-B 15-Apr 2.6 91.5 16.7 13-May 2.6 91.2 17.0 10-Jun 2.4 92.3 16.9 89xOL28-HO1-7-4-1-2-b2-B 15-Apr 32.6 75.1 16.4 13-May 50.8 73.7 15.8 10-Jun 33.4 75.3 15.4 90xOL61-HO2-1-1-b2-B 15-Apr 34.2 76.4 13.4 13-May 30.6 76.5 13.6 10-Jun 28.9 76.7 13.6 88x1B-OLBC1-6-1-3-1-b2-B 15-Apr 47.2 73.6 16.0 13-May 40.7 74.0 16.0 10-Jun 44.6 74.0 16.6 90x7-1-5-1-b2-B 15-Apr 2.3 91.4 18.1 13-May 2.2 92.1 18.5 10-Jun 2.0 93.0 18.4 Florunner 15-Apr 1.9 94.1 18.7 13-May 1.8 94.7 18.8 10-Jun 1.9 94.5 18.7 *data provided by Andersen and Gorbet (2002)

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Table 5-9: Statistical Significance for Fatty Acids Related to Planting Date, Variety, and Their Interaction

16:0 18:0 18:1 18:2 20:4n6 20:0 22:0 24:0 18:1/18:2 IV % saturation Statistics Variety *** *** *** *** *** *** *** *** *** *** *** Planting Date NS NS * * NS NS *** NS NS ** NS Plnt Date*Var NS ** ** * NS *** NS NS NS * NS NS=not significantly different; * denotes level of significance; Plnt=planting; Var=variety *data provided by Andersen and Gorbet (2002)

90 80 70 60 50 15-Apr 40 13-May 30 10-Jun % Oleic Acid 20 10 0

FMDR 98 Andru 93 Florunner Georgia GreenSun Oleic 97R 90x7-1-5-1-b2-B 86x13A-4-2-3-2-b3-B92xOL103-1-2-1-b2-B 90xOL61-HO2-1-1-b2-B 88x1B-OLBC1-6-1-3-1-b2-B Variety

*data provided by Andersen and Gorbet (2002)

Figure 5-1: Percent Oleic Acid for Peanut Genotypes Separated by Planting Date

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60 o 50

40 15-Apr 30 13-May 10-Jun 20

10 Oleic/Linoleic Acid Rati

FMDR 98 Andru 93 Florunner Sun Oleic 97R Georgia Green 90x7-1-5-1-b2-B 86x13A-4-2-3-2-b3-B92xOL103-1-2-1-b2-B 90xOL61-HO2-1-1-b2-B 88x1B-OLBC1-6-1-3-1-b2-B Variety

*data provided by Andersen and Gorbet (2002)

Figure 5-2: Oleic/Linoleic Acid Ratio for Peanut Genotypes Separated by Planting Date

CHAPTER 6 SUMMARY AND CONCLUSIONS

Peanut storage conditions have significant effects on overall quality, especially if the product is to maintain high quality over long periods of storage. High-oleic peanuts maintain best product quality (low oxidation, loss of crunchiness and maintenance of desirable flavor) when stored at water activities between 0.33 and 0.44. Above this range, crunchiness decreased and oxidation increased, whereas below the rate of oxidation increased.

Date of seed planting also plays a role in the overall quality and flavor potential of peanut genotypes, where runner-type peanuts are normally planted in early May in the

Southeastern region of the U.S. Other research regarding peanut quality noted that roast peanut flavor declines during storage regardless of variety. Peanut sweetness declined as roast peanut flavor increased regardless of variety or planting date. Planting date did not appear to effect roasted peanut flavor, sweetness, painty, or cardboardy sensory scores, with the exception of the 4-15-98 planting date. Typical planting dates in early May appear to be the best time to plant peanuts, as a function of sensory potential. SunOleic

97R (a high-oleic peanut) had the highest roasted peanut scores and the lowest levels of oxidation over a 6 months storage span. Fatty acid profile did not significantly change as a function of planting date. Several experimental lines showed oleic acid content similar to SunOleic97R, labeling them as high-oleic peanuts.

116 117

Solid-phase microextraction/gas chromatography/flame ionization detector is a rapid, non-destructive method for predicting peanut flavor in peanuts. Pyrazine compounds formed during peanut roasting, via Maillard browning, can be measured using SPME/GC/FID. Pyrazines correlated highly with roasted peanut flavor and aroma.

2,5-dimethylpyrazine may be the best overall pyrazine to measure as a predictor of roasted peanut flavor and aroma, due to high correlation coefficients, although 2,3,5- trimethylpyrazine seems to be a good indicator as well, especially in the case of Florida

MDR 98.

Roasting peanuts at 1750C for 15 minutes gave the highest sensory scores for roasted peanut flavor and aroma, the highest levels of total pyrazines, with the darkest color. Currently, color measurements are commonly used to predict peanut flavor.

Peanut genotypes differ in roasted flavor and aroma, regardless of roast color. Inclusion of pyrazine levels allows for more accurate optimization of roasting parameters when measuring roasted peanut quality.

APPENDIX A TASTE PANEL SHEETS FOR CHAPTER 3

First, please taste the reference sample. The chart below gives an overview of the flavor intensity levels for each attribute of the reference sample. Second, please rate the following samples from 1-9 for each flavor attribute (1 being less intense and 9 being more intense).

Reference sample: Roast Peanut:…….….7-8 Crunchy:……………. 7-8 Sweet:………………..5-6 Cardboardy:………….1-2 Painty:……………….1-2

Sample 786 Roast Peanut 1 2 3 4 5 6 7 8 9

Crunchy 1 2 3 4 5 6 7 8 9

Sweet 1 2 3 4 5 6 7 8 9

Cardboardy 1 2 3 4 5 6 7 8 9

Painty 1 2 3 4 5 6 7 8 9

118 119

Sample 652 Roast Peanut 1 2 3 4 5 6 7 8 9

Crunchy 1 2 3 4 5 6 7 8 9

Sweet 1 2 3 4 5 6 7 8 9

Cardboardy 1 2 3 4 5 6 7 8 9

Painty 1 2 3 4 5 6 7 8 9

Sample 121 Roast Peanut 1 2 3 4 5 6 7 8 9

Crunchy 1 2 3 4 5 6 7 8 9

Sweet 1 2 3 4 5 6 7 8 9

Cardboardy 1 2 3 4 5 6 7 8 9

Painty 1 2 3 4 5 6 7 8 9

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Sample 377 Roast Peanut 1 2 3 4 5 6 7 8 9

Crunchy 1 2 3 4 5 6 7 8 9

Sweet 1 2 3 4 5 6 7 8 9

Cardboardy 1 2 3 4 5 6 7 8 9

Painty 1 2 3 4 5 6 7 8 9

Sample 527 Roast Peanut 1 2 3 4 5 6 7 8 9

Crunchy 1 2 3 4 5 6 7 8 9

Sweet 1 2 3 4 5 6 7 8 9

Cardboardy 1 2 3 4 5 6 7 8 9

Painty 1 2 3 4 5 6 7 8 9

Please describe the differences (if any) between the samples:

APPENDIX B TASTE PANEL SHEET FOR CHAPTER 4

Sensory Evaluation of Peanuts

Welcome. Please taste the samples front to back, left to right. References for the attributes will be provided, as needed. Write the corresponding number from the labeled cup with a line like the example below. Take a sip of water in between samples to rinse your palate. If you need more water, knock on the sliding door and I’ll get you more.

Roast Peanut Aroma

None Extremely High Roast Peanut Flavor

None Extremely High Sweetness

None Extremely High Raw / Green / Beany

None Extremely High Bitter

None Extremely High Crunchiness

None Extremely High

Burnt Flavor Yes # No #

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APPENDIX C TASTE PANEL SHEETS FOR CHAPTER 5

Sensory Evaluation of Peanuts

Roast Peanut Flavor

Low High

Sweetness

Low High

Raw / Green / Beany

Low High

Cardboardy

Low High

Painty

Low High

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LIST OF REFERENCES

Ames, J.M., Bates, L., and MacDougall, D.B. 1994. Colour development in an intermediate moisture Maillard system. In: Maillard Reactions in Chemistry, Food, and Health. Labuza, T.P., Reineccius, G.A., Monnier, V.M., O’Brien, J., and Baynes, J.W. (eds.) Cambridge: Royal Society of Chemistry. p. 120-125

Andersen, P.C and Gorbet, D.W. 2002. Influence of year and planting date on fatty acid chemistry of high oleic acid and normal peanut genotypes. J. Agr. Food Chem. 50(5):1298-1305

Andersen, P.C., Hill, K., Gorbet, D.W., and Brodbeck, B.V. 1998. Fatty acid and amino acid profiles of selected peanut genotypes and breeding lines. Journal of Food Composition and Analysis. 11:100-111.

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BIOGRAPHICAL SKETCH

George L. Baker IV was born in Tampa, Florida, before moving 30 miles

northeast to Dade City. He attended preparatory school there until a golf scholarship

enticed him to Tallahasse, where he played for FAMU’s Rattlers. Two years later, he

relocated to Gainesville, receiving degrees from Santa Fe Community College and the

University of Florida. After receiving a bachelor’s degree in food science, he continued his graduate education at the University of Florida, completing his Ph.D. in food science in 2002.

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