DISSERTATION EFFECT OF FARM TO FORK OPERATIONS ON BIOACTIVE COMPOUNDS IN WHITE-FLESHED AND COLOR-FLESHED POTATOES Submitted by Fauzi Saleh Massoud Amer Department of Food Science and Human Nutrition In partial fulfillment of the requirements For the Degree of Doctor of Philosophy Colorado State University Fort Collins, Colorado Summer 2015 Doctoral Committee: Advisor: Jairam Vanamala Co-Advisor: Martha Stone Lavanya Reddivari David Holm Copyright by Fauzi Saleh Massoud Amer 2015 All Rights Reserved ABSTRACT EFFECT OF FARM TO FORK OPERATIONS ON BIOACTIVE COMPOUNDS IN WHITE- FLESHED AND COLOR-FLESHED POTATOES The potato, Solanum tuberosum L., is one of the most commonly consumed food crops worldwide, and is the leading vegetable crop in the United States with 69% of per capita consumption as processed potatoes. In addition to micro- and macro-nutrients, color-fleshed potatoes are one of the richest plant sources for health promoting components such as resistant starch, polyphenols, and carotenoids. In contrast, potatoes are well known to contain naturally occurring glycoalkaloids (GA; α-chaconine and α-solanine) and processing-induced acrylamide (AL). Potatoes can be stored up to one year before being processed/consumed and the effect of genotype, storage (4oC or 10oC; 3 or 6 months) and processing (baking and frying) on both toxic and health beneficial compounds remains unknown. We hypothesized that cultivar, storage and processing alters bioactive content in potato tuber and potato products. To test this hypothesis, raw, baked, and chipped of white-, yellow-, red-, and purple-fleshed potatoes from initial (fresh) and stored tubers were evaluated for AL/vitamin C and GAs using Ultra Performance Liquid Chromatography (UPLC) and High Performance Liquid Chromatography-Diode Array Detector (HPLC-DAD/UPLC-DAD), respectively. Total phenolic content (Folin - Ciocalteu reducing), anthocyanin content (pH differential method), antioxidant activity (DPPH and ABTS assay) were also determined. Raw potatoes were analyzed for reducing sugars (glucose and fructose) using a spectrophotometer. Sensory attributes (9-point hedonic scale) of baked and potato chips were assessed using untrained consumer panelists (n= 94 – 114). The content of GA/AL increased ii with storage, dependent on cultivar. Reducing sugar content in raw potatoes increased with storage, thereby, AL content in potato chips positively correlated with reducing sugars. Purple- fleshed potatoes had higher (p ≤ 0.05) total phenolic content, anthocyanin content, and antioxidant activity than red-fleshed potatoes and white-fleshed potatoes. The interaction effect of storage time and temperature on total phenolic content, anthocyanin content, and antioxidant activity was genotype-dependent. Baking led to a significant (p ≤ 0.05) increase in total phenolic content, anthocyanin content, and antioxidant activity; whereas chipping led to significant losses in total phenolic content, anthocyanin content, and antioxidant activity. However, red- and purple-fleshed potatoes could serve as potential sources of non-nutrient health-benefiting compounds in the human diet even after storage and processing. Vitamin C content in potato tubers and processed potatoes was genotype-dependent. Vitamin C content rapidly declined with storage after six months of storage irrespective of storage temperature (4°C or 10°C). Chipping and frying resulted in significantly reduced vitamin C levels compared to baked potatoes and unprocessed potatoes among all tested cultivars. An increase in GA and AL content, bioactive compounds, and antioxidant activity found with storage was cultivar dependent. However, vitamin C decreased with storage. Thus, it is critical to measure GA and AL content not only in the fresh tubers but also in the final potato products such as baked and chipped potatoes. It is critical to adjust food systems processes to consistently deliver lower GA and AL content, while retaining the beneficial bioactives, vitamin C, and sensory attributes of the final potato products. Adjusting farm-to-fork operations to retain the health-benefiting compounds in food crops while reducing natural and process-induced toxicants will aid in countering growing epidemic of chronic diseases globally. iii ACKNOWLEDGEMENTS I would like to thank my advisor Dr. Jairam Vanamala for giving me a chance to work in his laboratory to pursue my graduate program. His guidance, encouragement, and recommendation helped me accomplish this great task. His passion for science made me push harder each day and complete my work with dedication. His help is appreciated in making me become a better scientist. I want to express my gratitude to Dr. Lavanya Reddivari. She taught me most of the technical laboratory skills I needed. She is a crucial element in this dissertation was actively involved right from the experimental design until writing up the results. I thank all my lab members over the years: Sridhar Radhakrishnan, Gaurav Madiwale, Venkata Charepalli, Aaron Massey, Emily Poole, Amulya Balumuri and Orlando Perez for their help with the study and their awesome company in the lab. I also want to thank Dr. Martha Stone for her help support through the sensory attributes survey; it was impossible to conduct my studies without her help. I also thank the members of Dr. Martha Stone’s lab and Laura Markham for their help during the sensory evaluation. I also thank my other committee members, Dr. David Holm and his group for their help to collect potatoes and process them for my study. I extend special thanks to Dr. Michael Pagliassotti, Head of the Department of Food Science and Human Nutrition, who supported me after Dr. Jairam’s departure to Penn State University. I wish to thank every member of the Department of Food Science Human Nutrition at Colorado State University for their continuous help and support at different periods of my work. iv Finally, I would like to thank all my friends from Libya at Colorado State University for making my time while earning my Ph.D. a memorable one. I give heartfelt thanks to those whom I have missed to acknowledge. v DEDICATION This dissertation is dedicated to my mother, pure spirit, Mrs. Fatima A. Amer and my father Mr. Saleh Massoud Amer, whose unconditional love and support made this possible. I also dedicate this work to each member of my family and friends in Libya and the USA for their constant words of encouragement. vi TABLE OF CONTENTS ABSTRACT .................................................................................................................................. ii ACKNOWLEDGEMENTS ......................................................................................................... iv DEDICATION ............................................................................................................................. vi LIST OF TABLES ....................................................................................................................... xii LIST OF FIGURES ................................................................................................................... xiii CHAPTER ONE INTRODUCTION ............................................................................................. 1 CHAPTER TWO REVIEW OF LITERATURE ........................................................................... 5 1. Introduction to the potato ......................................................................................................... 5 1.1. The history of the potato ................................................................................................ 5 1.2. Potato growth ................................................................................................................. 6 1.3. Potato physiology .......................................................................................................... 7 1.4. Potato cultivars .............................................................................................................. 8 2. Toxic compounds found in potatoes .......................................................................................... 9 2.1. The post-processing toxic compound: Acrylamide ....................................................... 9 2.1.1. Acrylamide formation ................................................................................................. 9 2.1.2. Factors that affect acrylamide content in potato products ........................................ 11 2.1.3. Acrylamide and health .............................................................................................. 12 2.1.4. Effect of processing on acrylamide in potato products ............................................. 13 2.2 The pre-processing toxic compound: Glycoalkaloids................................................... 17 2.2.1. Glycoalkaloids pathway ............................................................................................ 17 2.2.2. Glycoalkaloids and health ......................................................................................... 18 vii 2.2.3. Factors that affect glycoalkaloid content in potatoes ................................................ 19 2.2.3.1. Effect of genotype and post-harvest factors on glycoalkaloids ............................. 19 2.2.3.2. Effect of processing on glycoalkaloids .................................................................. 20 3. Potato bioactive compounds ...................................................................................................