ABSTRACT LEKSRISOMPONG, PATTARIN. Application of Sensory Techniques to Understand the Impact of Ingredients on Sensory Properties of Beverages. (Under the direction of Dr. MaryAnne Drake.) Sensory evaluation is a critical process in product development and consumer research. It is a fast growing field with novel techniques being developed and evaluated continuously. The objective of this dissertation was to apply different sensory science techniques, both traditional and newly developed approaches, to aid in the understanding of the impact of ingredients on sensory properties of beverages. Four different studies were conducted on two types of beverages/ingredients: whey protein hydrolysate beverages and carbonated lemon-lime beverages. Whey protein hydrolysate (WPH) is a value-added dairy ingredient with bioactive and functional properties. However, the flavor and bitter taste of WPH limits its usage. First, chemical compounds that contributed to flavor of whey protein hydrolysate were characterized. Gas-chromatography olfactometry and mass spectrometry, descriptive analysis, and threshold testing were conducted. Potato/brothy, malty, and animal flavors and bitter taste were key distinguishing sensory attributes of WPH. Important aroma-active compounds that contributed to WPH flavors were methional (potato/brothy flavor) and 3- methyl butanal (malty flavor). The second study evaluated effectiveness of 24 documented bitter taste inhibitors to decrease WPH bitterness. Quinine hydrochloride (Quinine) was used as a control. Effective bitter taste inhibitors of WPH tested were sucralose, fructose, sucrose, adenosine 5’ monophosphate, adenosine 5’monophosphate disodium, sodium acetate, monosodium glutamate and sodium gluconate. All effective inhibitors in rehydrated WPH were also effective in beverage applications. Descriptive analysis demonstrated that sweeteners enhanced vanilla and chocolate flavors in beverages. Most salts and a nucleotide were effective bitter inhibitors but suppressed vanilla and chocolate flavors and potentiated other flavors and basic tastes. The second topic of this dissertation was to study the sensory properties and consumer preferences of diet and regular carbonated soft drinks (CSD). In the first study, descriptive analysis and degree of difference from control methods (DOD) were applied to document sensory properties of regular and diet carbonated soft drinks. Multidimensional scaling was used to interpret DOD data and Partial Least Squares Regression (PLS2) and Generalized Procrustes Analysis (GPA) were used to predict and relate the two sensory data sets. Beverages were distinguished based on category, sweetening systems and brand. The use of DOD allowed clarification of the underlying perceptions that trained panelists used in differentiating samples. The developed lexicon allowed for documentation of multi-modal sensory perceptions generated by carbonated beverages. From this study, ten beverages were selected for a subsequent study to identify drivers of liking. Consumer testing with regular and diet beverages, consumer segmentation and external preference mapping were performed. Diet beverage consumers liked two of the diet beverages more than regular beverage consumers. There were no differences in the overall liking scores between diet and regular beverage consumers for other products except for a sparkling beverage sweetened with juice which was more liked by regular beverage consumers. Three subtle but distinct consumer preference clusters were identified. All clusters were driven by mouthfeel attributes but were differentiated by preference for basic tastes and some aromatics while user status (diet or regular beverage consumers) did not have a large impact on liking. Multiple sensory tools used in combination with statistical analyses successfully allowed for understanding of sensory characteristics of different types of beverages and the impact of ingredients in beverages. © Copyright 2011 by Pattarin Leksrisompong All Rights Reserved Application of Sensory Techniques to Understand the Impact of Ingredients on Sensory Properties of Beverages by Pattarin Leksrisompong A dissertation submitted to the Graduate Faculty of North Carolina State University in partial fulfillment of the requirements for the degree of Doctor of Philosophy Food Science Raleigh, North Carolina 2012 APPROVED BY: _______________________________ ______________________________ Dr. MaryAnne Drake Dr. Allen Foegeding Committee Chair ________________________________ ________________________________ Dr. Timothy Sanders Dr. Brian Farkas DEDICATION This dissertation is dedicated to my parents. ii BIOGRAPHY Pattarin Leksrisompong (Pat) was born on the 17th of February, 1985 in Bangkok, Thailand. She was the youngest child out of the 4 daughters of Mr. Vinai and Ms. Phatanee Leksrisompong. She graduated her secondary school education from the New International School of Thailand (NIST) in 2003 with an International Baccalaureate Diploma. After graduation, she moved to the United States to continue her education. She started her Bachelor of Science degree in Food Science at North Carolina State University, Raleigh, North Carolina in the fall of 2003. Her major undergraduate advisor was Dr. Lynn Turner. She received her B.S. degree in Food Science, graduated summa cum laude, and had a minor in Chinese Studies, in May 2007. Soon after that, she pursued a Master’s degree in Food Science and continued on for her Ph.D under the direction of Dr. MaryAnne Drake at North Carolina State University. iii ACKNOWLEDGMENTS I would like to thank my parents, Mr. Vinai and Ms. Phatanee Leksrisompong for all the love and support throughout the years, for great opportunities and providing for me to come this far in my academic career. To my sisters; Tippy, Nike and Nino – thank you for your friendship and making Raleigh so much like home. I love you all very much. To Dr. Drake, thank you for all that you have done for me. The advice, support, and opportunities you have given me meant so much and they are tremendously appreciated. I could not have asked for a better advisor. You have helped me grow into a person I never knew I could become. To my committee: Drs. Foegeding, Farkas and Sanders - thank you for challenging me with things I overlooked, and allowing me to think outside the box. Dr. Foegeding, thank you for teaching me Food Chemistry! You have given me a solid foundation. Also, thank you for all thought provoking questions and made me a better scientist. Dr. Farkas, thank you for being so helpful with every little thing ever since undergrad. In addition, thank you for taking the time to help me with putting my skills on paper. I really appreciate it. To Dr. Sanders, thank you for always be available whenever I need some advice, and for being so kind. I would also like to thank Dr. Kannapon Lopetcharat for his advice on statistics, and for always having time to help. Thank you Dr. Brian Guthrie for interesting projects I got the iv chance to work on. Both of you have contributed to my future goals and plans. Thank you so much for everything. To Dr. Brake – you made me feel like I have a parent in Raleigh. Thank you for being there whenever I need. To the Drake lab members: Sue Jervis, Samantha White, Lakendra Shepard, Jamie Kang, Rachel Campbell, Mina Kim, Neerja Desai, Echo Li, Tucker Smith, Aaron Fox, Curtis Park and Kristin Frankowski as well as Jessica Childs, Iris Liaw and Adam Croissant- you all are the most incredible individuals and are the best group of people I could work with. We work so often as a team and it helped tremendously to work with such great people. To Michele Yates – thank you for being there for me and always listening to me when I need someone to talk to. To Evan Miracle –thank you for all your help and input when I come across funky results in my projects. Also thanks for making this lab run smoothly – you are Mr. Miracle! Lastly, I’d like to acknowledge all of my professors that had taught me throughout these years. Everyone at Schaub including all the staff and faculty as well as my fellow graduate students for a great work place environment. v TABLE OF CONTENTS LIST OF TABLES ...................................................................................................................x LIST OF FIGURES ............................................................................................................ xiii Chapter 1. LITERATURE REVIEW .......................................................................................1 A. Introduction ........................................................................................................................2 B. Physiology of Bitter Taste Receptors and Bitter Taste Transduction in General .......4 1. Bitter Taste Receptors ...................................................................................................4 2. Structure of T2R and its Tastant-Receptor Interactions ................................................7 3. Bitter Taste Transduction .............................................................................................10 4. Individual Sensitivity to Tastants .................................................................................13 C. Bitter Taste Peptides, Receptors, and Binding Site .....................................................15 1. Studies of bitter taste receptors for peptides ................................................................15 2. Bitter Peptides ..............................................................................................................16