Application of Untargeted Flavoromic Analysis to Characterize Chemical Drivers of Coffee Quality Dissertation Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University By Sichaya Sittipod, M.S. Graduate Program in Food Science and Technology The Ohio State University 2019 Dissertation Committee Devin G. Peterson, Advisor Luis E. Rodriguez-Saona Christopher T. Simons Emmanouil Chatzakis Copyrighted by Sichaya Sittipod 2019 Abstract Increasing global demand for premium coffee beverages has challenged coffee producers to provide higher quality products. The overall aim of this project was to characterize the chemical composition of coffee brews that contribute to different flavor quality and ultimately to provide a chemical basis for the optimization of coffee production. During the initial phase of this study, current industrial methods for green bean selection were evaluated in regard to their ability to predict coffee brew sensory properties. Physico- chemical changes observed in the green coffee beans stored under different conditions were not indicative of coffee brew flavor changes in this study. Overall, these results supported the need to develop new methods for coffee quality prediction. In the second phase of this project, an untargeted Liquid Chromatography/Mass Spectrometry (LC/MS) Flavoromics approach was used to define chemical markers predictive of coffee brew quality. Eighteen coffees ranging in qualities from below specialty to excellent specialty quality, were chemically profiled and modeled against the official Specialty Coffee Association cup score (obtained by Q-graders) using Orthogonal Partial Least Square (OPLS). A successful model was generated and showed high prediction ability (R2Y=0.99, Q2=0.97). A total of 10 highly predictive compounds were selected, of which six were positively and four were negatively correlated to cup score. Their sensory impact was evaluated using a recombination study performed by five Q-graders. Addition of the compounds individually ii and in combination to a coffee brew base caused significant changes in cup scores. Three compounds predictive of high cup score: 3-O-caffeoyl-1-O-3-methylbutanoylquinic acid (m/z 437), 3-O-caffeoyl-1-O-3-methylbutanoyl-1, 5-quinide (m/z 419) and a chlorogenic acid derivative (m/z 671) significantly increased the quality of a below specialty grade coffee brew to excellent specialty grade. Four compounds predictive of low cup score: ent- 16α,17-dihydroxy-kauran-19-diglucoside (m/z 659), its aglycone form ent-16α,17- dihydroxy-kauran-19-oic acid (m/z 335), unknown compounds m/z 351 and m/z 9.48_333 significantly decreased the coffee quality score of a high cup score coffee. All the identified compounds had no or slight flavor activity when evaluated in water at the levels present in coffee. Yet they were able to significantly modulate the flavor of coffee, likely through the existence of perceptive interactions. The presence of these seven markers of coffee brew quality in the green bean was further investigated. Markers 3-O-caffeoyl-1-O-3- methylbutanoylquinic acid and ent-16α,17-dihydroxy-kauran-19-diglucoside were both detected in green coffee beans at levels correlated to the coffee brew cup scores. Overall, this research showed a successful application of a newer flavor analysis method, Flavoromics, that allowed for the discovery of seven flavor compounds predictive of the coffee cup quality. These compounds can be used as markers of quality for raw material selection and process optimization to achieve desirable coffee brew flavor. iii Dedication To my mother and sister who have sacrificed so much for my education and growth iv Acknowledgments First, I would like to express sincere gratitude towards my advisor Dr. Devin G. Peterson for giving me the opportunity to work under his mentorship at FREC. He always believed in me and helped guide me, as I struggled to overcome various challenges during these past 4 years. Thank you for pushing me to become my best. These valuable experiences and lessons will stay with me as I continue on to my professional career and life. I would also like to thank all of my committee members, Dr. Rodriguez, Dr. Simons, Dr. Hatzakis, and Dr. Alonso for their inputs and suggestions these 2 years at OSU. I owe so much gratitude towards Dr. Laurianne Paravisini for her mentorship and friendship over the years. I will forever be thankful for her kindness and all the things she has taught me. It has been a crazy, long journey and she was there supporting me every single step of the way. I would like to acknowledge Dr. Eric Schwartz, Dr. Sagar Desphande, and Dr. Smaro Kokkinidou for their advice and help towards my research. Special thanks to Julie Peterson for her guidance, and her kind, encouraging words. I would also like to thank Laurie Serianni and the coffee team at Keurig Green Mountain Inc. for their valuable assistance with sample sourcing and sensory evaluation for this research. Many thanks to my current lab mates at OSU and former lab mates and staff in Minnesota, whom have each supported me in their own special ways. Thanks for the good times that makes up for all those the long days and nights at the lab. v Lastly, I would like to thank the very important people in my life. I would like to thank my family and friends, here and a far, whom have sent their love and cheered me on throughout my pursuit for a PhD. And very special thanks to Kevin Wong, for being so kind and understanding through the difficult times and always being there for me. vi Vita 2006- 2010………………………B.S. Food Science and Technology Kasetsart University, Thailand 2012-2014………………………M.S. Grain Science and Industry, Kansas State University, USA 2014-2016………………………Graduate Research Associate, Flavor Research and Education Center, Department of Food Science and Nutrition, University of Minnesota, USA Publications Sittipod, Sichaya and Shi, Yong-Cheng. Changes of starch during parboiling of rice kernel. Journal of Cereal Science. 2016. 69, 238-244. Sittipod, Sichaya and Shi, Yong-Cheng. Changes in physicochemical properties of rice starch during steeping in the parboiling process. Journal of Cereal Science. 2016. 69, 398-405. Bian, Qi, Sittipod, Sichaya, Garg, Anubha, Ambrose, Kingsly. Bulk flow properties of hard and soft wheat flours. Journal of Cereal Science. 2015. 63, 88-94. Fields of Study Major Field: Food Science and Technology vii Table of Contents Abstract ............................................................................................................................... ii Dedication .......................................................................................................................... iv Acknowledgments ............................................................................................................... v Vita .................................................................................................................................... vii List of Tables ..................................................................................................................... xi List of Figures ................................................................................................................... xii Chapter 1. Introduction ....................................................................................................... 1 Research objectives ......................................................................................................... 2 Chapter 2. Literature Review .............................................................................................. 4 1. Coffee .......................................................................................................................... 5 1.1 Green coffee bean composition ............................................................................ 5 1.2 Coffee flavor generation ....................................................................................... 8 1.3 Coffee brew flavor ................................................................................................ 9 2. Coffee quality ............................................................................................................ 12 2.1 Physical evaluation ............................................................................................. 13 2.2 Sensory evaluation .............................................................................................. 13 2.3 Chemometrics: combine sensory and chemistry ................................................. 17 viii 3. Factors impacting quality .......................................................................................... 18 4. Methods to uncover coffee flavor ............................................................................. 22 4.1 Targeted flavor analysis ...................................................................................... 22 4.2 Untargeted analysis (Flavoromics) ..................................................................... 24 5. Summary ................................................................................................................... 30 Chapter 3. Investigation of physico-chemical properties of green coffee beans as predictors of sensory properties of coffee brew ................................................................ 31 1. Introduction ..............................................................................................................