Influence of Beer Color on Perception of Bitterness a Thesis Submitted To
Total Page:16
File Type:pdf, Size:1020Kb
Influence of Beer Color on Perception of Bitterness A Thesis Submitted to the Faculty of Drexel University by Joseph William Spearot in partial fulfillment of the requirements for the degree of Master of Science in Food Science March 2016 © Copyright 2016 Joseph William Spearot. All Rights Reserved. iii Dedications To my family and friends. Without your constant encouragement, support, and love I would be lost. iv Acknowledgements First and foremost I would like to thank my research mentor, Dr. Jake Lahne, encouraging my research and being an invaluable source of support and knowledge. From IRB approval to quick emails about proper spit cups to helping explain the complexities I cannot thank him enough. Additionally, I would like to thank Nick Rodgers, sensory extraordinaire for Yards Brewing Company, for his help in setting up, running, and recruiting for the two sensory studies run at Yards. I would also like to thank Frank Winslow and Lena Jonsson of the Quality Assurance lab of Yards Brewing Company for their help in planning, running, and taking interest in my research. Many thanks go to fellow MS in Food Science students Pradnya Rao, Urvi Shah, and Nidhi Champaneri for their help in setting up and running the sensory study at Drexel. Additionally, I would like to acknowledge the comments and guidance of my thesis committee including Dr. Steven Wrenn, of the Chemical and Biological Engineering department, and Dr. Brandy-Joe Milliron, of the College of Nursing and Health Professions. Finally, I’d like to thank all those who took interest in my research, participated in my studies, and helped at any step along the way. v Table of Contents List of Tables ................................................................................................................................. vi List of Illustrations ........................................................................................................................ vii Abstract ........................................................................................................................................ viii 1. Introduction ............................................................................................................................... 1 2. Literature Review ...................................................................................................................... 3 I. Introduction ................................................................................................................. 3 II. Background and the Brewing Process ......................................................................... 4 III. Beer in the United States ............................................................................................. 8 IV. Beer Color ................................................................................................................. 12 i. Malt and Color Extraction ............................................................................. 12 ii. Measurement of Color ................................................................................... 14 iii. Darkening Techniques ................................................................................... 15 V. Beer Bitterness ........................................................................................................... 17 i. Hops and Bitterness Extraction ..................................................................... 17 ii. Measurement of Bitterness ............................................................................ 20 iii. Perception of Bitterness ................................................................................ 22 VI. Sensory Evaluation .................................................................................................... 25 VII. Relationship between Color and Flavor .................................................................... 28 VIII. Specific Objectives .................................................................................................... 32 IX. Hypotheses ................................................................................................................ 33 X. Figures and Tables ..................................................................................................... 34 3. Beer Production and The Brewing Process ............................................................................ 38 I. Materials and Methods .............................................................................................. 38 II. Results ....................................................................................................................... 41 III. Discussion .................................................................................................................. 42 IV. Figures and Tables ..................................................................................................... 43 4. Biological and Chemical Analyses ......................................................................................... 46 I. Materials and Methods .............................................................................................. 46 II. Results ....................................................................................................................... 48 III. Discussion .................................................................................................................. 49 IV. Figures and Tables ..................................................................................................... 50 5. Sensory Studies ....................................................................................................................... 53 I. Materials and Methods .............................................................................................. 53 II. Results ....................................................................................................................... 56 III. Discussion .................................................................................................................. 58 IV. Figures and Tables ..................................................................................................... 61 6. Conclusions ............................................................................................................................. 67 7. References ............................................................................................................................... 69 8. Appendix A: Sensory Test Materials ...................................................................................... 76 9. Appendix B: Raw Chemical Analysis Data ............................................................................ 85 10. Appendix C: Raw Sensory Analysis Data .............................................................................. 87 vi List of Tables Table 1: Summary of Microbiological Testing Results ................................................................ 51 Table 2: Color and Bitterness of Darkening Technique Beers ..................................................... 52 Table 3 Color and Bitterness of Color Perception Testing Beers ................................................. 52 Table 4: Color Versus Attribute One-Way ANOVA Results ....................................................... 62 Table 5: Expertise Two-Way ANOVA Results ............................................................................ 64 Table 6: Summary of Color Perception Discrimination Test ....................................................... 66 vii List of Figures Figure 1: Overview of Brewing .................................................................................................... 34 Figure 2: Malt Types ..................................................................................................................... 35 Figure 3 EBC/SRM Scale ............................................................................................................. 35 Figure 4: Hop Flower Anatomy .................................................................................................... 36 Figure 5: Compounds Extracted from Hops ................................................................................. 36 Figure 6: Isomerization of Alpha Acids ........................................................................................ 37 Figure 7: G Protein Pathway ......................................................................................................... 37 Figure 8: Specialty Ingredients used during Brewing ................................................................... 43 Figure 9: Overview of Brewing Protocol ...................................................................................... 44 Figure 10: Final Beer (Color Perception) Products ...................................................................... 45 Figure 11: Carbonation Testing Equipment .................................................................................. 50 Figure 12: Yeast Microscopy ........................................................................................................ 51 Figure 13: Statistical Results of Color Perception Testing ........................................................... 61 Figure 14: Effect of Beer Color on Bitterness Perception ............................................................ 63 Figure 15: Effect of Expertise on Saltiness and Liking ...............................................................