AN ABSTRACT OF THE THESIS OF Pam A. Hartwig for the degree of Master of Science in Food Science and Technology presented on September 2,1994. Title: Flavor Characterization of Selected Acidulants in Model and Food Systems Abstract approved by: Mina R. McDaniel Acidulants can contribute considerably to the flavor of food. However, limited research on differences in acid flavor exists. While numerous researchers have studied acids, most have focused on sourness exclusively. Acids have been shown previously to differ in non-sour components, such as bitterness and astringency. A series of experiments were conducted to determine flavor characteristics of selected acids in different systems. First, selected acids (lactic, malic, citric, acetic) and 2 acid blends (lactic/acetic 1:1 and 2:1) in a model (water) system were evaluated on an equivalent weight (0.2% w/v) and on an equivalent pH basis. Three pH levels were explored: 3.5, 4.5 and 6.5. The technique of free-choice profiling was applied to characterize the flavor profile. Results analyzed by generalized procrustes analysis showed two significant findings: (1) acids differ in sensory character, and (2) the flavor of an acid changes with pH. Second, selected acids (lactic, malic, citric, tartaric) were evaluated in sweetened, flavored drinks on an equivalent weight basis at two concentrations (0.4 and 0.6% w/v). Four flavors were evaluated: orange, cherry, cola and strawberry. Descriptive analysis was used, and the data was analyzed by principal component analysis. Significant differences were found on among acids and concentrations. For the orange flavor system, citric acid enhanced the orange flavor of the drink. Third, selected acids (lactic, citric, acetic) and 2 acid blends (acetic/lactic 1:1 and 2:1) were evaluated in emulsions on an equivalent pH basis. Three pH levels were explored: 3.5, 4.5 and 5.5. These findings support the first study as differences were found among acids, and flavor changes existed when pH changed. cCopyright by Pam A. Hartwig September 2,1994 All Rights Reserved Flavor Characterization of Selected Acidulants in Model and Food Systems bjr Pam A. Hartwig A THESIS submitted to Oregon State University in partial fulfillment of the requirements for the degree of Master of Science Completed September 2, 1994 Commencement June 1995 APPROVED: ——• J - - - i^,. ^ , , j -;_ t Professor of Food Science and Technology in charge of major -<r Ti- 7, .it IT WTfc J *— p e ,, — ■■-■J ., -w ^, .._ Head of Department of Food Science and Technology »'i'i\,^,'tv/v''t*y Dean of Graduate School Date thesis presented: September 2,1994 Typed by the author: Pam A. Hartwig ACKNOWLEDGEMENTS I would like to thank Dr. Mina R. McDaniel for giving me direction and encouragement which made this all possible. She introduced me to the World of Food Science when I was lost, and then she challenged me and kept me motivated when I decided to continue my education under her. I am thankful to PURAC America for supporting this research. Special thanks to Arielle de Jong, Edwin Bontenbal and Rinske Potjewijd who were instrumental in getting me this grant and guiding the research. I thank my committee members, professors, and all those in the department who shared their knowledge, time, and encouragement to help me reach this goal. I am grateful for all the advice and support I received from the sensory group in the last few years (Steven H., Jennifer Jo W., Debbie B., Sonia R., Cindy L., Cida R., Renee, Andrea, Rusty, Ann D., Anne P., Lee Ann C, and Greg S.). Special thanks to Andrea Rodakowski for preparing the emulsions, Sonia Rubico for all the statistics guidance, and Greg Stuckey for helping with my slides. I also thank Rick McGill for his support this last year in trying to keep me together. Most importantly, I want to thank my family (Mom, Dad, Paul) for their unconditional love and encouragement that made this all possible. I couldn't have survived this last year without such an incredible support system. Table of Contents Page 1. Introduction 1 2. Literature Review 4 2.1 Acids 4 2.1.1 Acetic 4 2.1.2 Citric 9 2.1.3 Lactic 11 2.1.4 Malic 15 2.1.5 Tartaric ; 17 2.1.6 Lactic/Acetic Combinations 20 2.2 Taste Perception 21 2.2.1 Sourness 23 2.2.2 Astringency 26 2.3 Descriptive Analysis 29 2.3.1 Flavor Profile Method 29 2.3.2 New Methods 30 2.3.3 Free-Choice Profiling 31 2.4 Statistical Analysis 33 2.4.1 Generalized Procrustes Analysis 33 2.4.2 Principal Component Analysis 34 3. Flavor Characteristics of Lactic, Malic, Citric and Acetic Acids at Various pH Levels 37 3.1 Abstract 38 3.2 Introduction 39 3.3 Materials and Methods 41 3.3.1 Samples 41 3.3.2 pH Determinations 42 Table of Contents (continued) Page 3.3.3 Panelists 42 3.3.4 Presentation of Samples 43 3.3.5 Training 43 3.3.6 Statistical Analysis 44 3.4 Results and Discussion 45 3.4.1 Sensory Results 45 3.4.2 Panelist and Sample Variation 57 3.5 Conclusions 59 3.6 References 60 4. Flavor Characteristics of Lactic, Malic, Citric and Tartaric Acids in Sweetened, Flavored Drinks 62 4.1 Abstract 63 4.2 Introduction 64 4.3 Materials and Methods 65 4.3.1 Samples 65 4.3.2 Panelists 66 4.3.3 Presentation of Samples 66 4.3.4 Training 67 4.3.5 Statistical Analysis 67 4.4 Results 68 4.4.1 Orange 69 4.4.2 Cherry 75 4.4.3 Cola 75 4.4.4 Strawberry 85 4.5 Discussion 85 4.5.1 Sourness and Overall Intensity 85 Table of Contents (continued) Page 4.5.2 Sweetness 91 4.5.3 Astringency 92 4.5.4 Flavor 93 4.6 Conclusions 94 4.7 References 94 5. Flavor Characteristics of Emulsions Containing Lactic, Citric, and Acetic Acids 96 5.1 Abstract 97 5.2 Introduction 98 5.3 Materials and Methods 99 5.3.1 Samples 99 5.3.2 Preparation of Samples 100 5.3.3 pH Determinations 101 5.3.4 Panelists 101 5.3.5 Presentation of Samples 101 5.3.6 Training 102 5.3.7 Statistical Analysis 103 5.4 Results and Discussion 103 5.5 Conclusions Ill 5.6 References Ill 6. Overall Conclusions 113 7. Bibliography 115 List of Figures Figure Description Page 2.1 Chemical structures of acidulants 6 3.1 Sample consensus plot for free-choice profiling of acids following generalized procrustes analysis: principal axes 1 vs. 2 50 3.2 Sample consensus plot for free-choice profiling of acids following generalized procrustes analysis: principal axes 1 vs. 3 51 3.3 Percentages consensus and within (residual) variation distributed over 18 samples 58 4.1 Sample consensus plot for the orange flavored drinks following principal component analysis of descriptive analysis data: principal axes 1 vs. 2 71 4.2 Mean intensity ratings for acids on 5 descriptors at 2 concentrations for orange flavored drinks 74 4.3 Sample consensus plot for the cherry flavored drinks following principal component analysis of descriptive analysis data: principal axes 1 vs. 2 77 4.4 Mean intensity ratings for acids on 5 descriptors at 2 concentrations for cherry flavored drinks 79 4.5 Sample consensus plot for the cola flavored drinks following principal component analysis of descriptive analysis data: principal axes 1 vs. 2 82 4.6 Mean intensity ratings for acids on 5 descriptors at 2 concentrations for cola flavored drinks 84 List of Figures (continued) Figure Description Page 4.7 Sample consensus plot for the strawberry flavored drinks following principal component analysis of descriptive analysis data: principal axes 1 vs. 2 87 4.8 Mean intensity ratings for acids on 5 descriptors at 2 concentrations for strawberry flavored drinks 89 5.1 Sample consensus plot for emulsions following principal component analysis of descriptive analysis data: principal axes 1 vs. 2 106 List of Tables Table Description Page 2.1 Key properties of acidulants 5 3.1 Terms generated by each panelist in the free-choice profiling of acids 46 3.2 Principal axis 1: mean scores for acids at 3 pH levels 47 3.3 Principal axis 2: mean scores for acids at 3 pH levels 48 3.4 Principal axis 3: mean scores for acids at 3 pH levels 49 3.5 Loadings* of descriptors for the first three principal axes following free-choice profiling of acids at 3 pH levels 52 3.6 Means1 and standard deviations2 of NaOH added in mmoles to acids to achieve 3 pH levels 56 4.1 Principal axis mean scores for orange flavored drinks 70 4.2 Mean intensity ratings* for acid by concentration interaction on orange flavored drinks 73 4.3 Principal axis mean scores for cherry flavored drinks 76 4.4 Mean intensity ratings* for acid by concentration interaction on cherry flavored drinks 78 4.5 Principal axis mean scores for cola flavored drinks 81 4.6 Mean intensity ratings* for 4 acid by concentration interaction on cola flavored drinks 83 4.7 Principal axis mean scores for strawberry flavored drinks .... 86 List of Tables (continued) Table Description Page 4.8 Mean intensity ratings* for acid by concentration interaction on strawberry flavored drinks 88 5.1 Principal axis mean scores for emulsions 105 5.2 Means1 and standard deviations2 of acid added to emulsions in mmoles to achieve pH levels 107 5.3 Mean intensity ratings* for emulsions 110 Flavor Characterization of Selected Acidulants in Model and Food Systems 1.