A STUDY OF BLANC DU BOIS WINE QUALITY By ERIC DREYER A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE UNIVERSITY OF FLORIDA 2010 1 © 2010 Eric Dreyer 2 To my parents 3 ACKNOWLEDGMENTS I thank the UF Food Science and Human Nutrition Department and my committee – Dr. Goodrich, Dr. Gray, Dr. Welt, and especially Dr. Sims and Dr. Rouseff – for their guidance throughout this study. I also thank Emma, my family, and my friends for their support. I thank Jack Smoot and June Rouseff at the CREC for their assistance with the chromatography equipment. I thank my lab mates – Adilia, Lorenzo, Dr. Odabasi, Reneé, and Sonia – for their help. I thank my wine panelists who stuck with me through 30 sessions of training and tasting. Finally, I thank all the wineries who provided wines for this study. 4 TABLE OF CONTENTS page ACKNOWLEDGMENTS .................................................................................................. 4 LIST OF TABLES ............................................................................................................ 7 LIST OF FIGURES .......................................................................................................... 8 ABSTRACT ..................................................................................................................... 9 CHAPTER 1 INTRODUCTION .................................................................................................... 12 2 LITERATURE REVIEW .......................................................................................... 14 Blanc Du Bois Pedigree .......................................................................................... 14 Pierce’s Disease ..................................................................................................... 14 Blanc Du Bois Growth Characteristics .................................................................... 15 Defining Wine Quality ............................................................................................. 16 Wine Sensory Analysis ........................................................................................... 17 Descriptive Analysis ................................................................................................ 19 Training ............................................................................................................ 20 Wine Studies That Have Employed Descriptive Analysis ................................. 22 Wine Chemistry ...................................................................................................... 24 Alcohols ............................................................................................................ 26 Sugars .............................................................................................................. 28 Volatiles ............................................................................................................ 28 Terpenes .................................................................................................... 30 Hydrocarbons ............................................................................................. 31 Aldehydes .................................................................................................. 31 Ketones ...................................................................................................... 32 Sulfur compounds ...................................................................................... 32 Phenolics ................................................................................................... 33 Amine compounds ..................................................................................... 34 Esters ......................................................................................................... 34 Acids .......................................................................................................... 37 3 METHODS .............................................................................................................. 41 Wine Selection ........................................................................................................ 41 Wine Quality Evaluation .......................................................................................... 41 Descriptive Analysis Panel ...................................................................................... 41 Panelist Selection ............................................................................................. 41 Panelist Training ............................................................................................... 42 Wine Attribute Intensity Evaluation ................................................................... 45 5 Chemical Analysis .................................................................................................. 45 Gas Chromatography Aroma Volatile Analysis ....................................................... 46 Statistical Analysis .................................................................................................. 49 4 RESULTS and DISCUSSION ................................................................................. 52 Quality Judging ....................................................................................................... 52 Descriptive Analysis Term Generation .................................................................... 53 Sensory, Chemical, and Volatile Correlations ......................................................... 53 Chemical Analysis .................................................................................................. 64 Principal Component and Cluster Analyses ............................................................ 67 Principal Component Analysis: DA and Chemical Data ................................... 67 Cluster Analysis: DA and Chemical Data ......................................................... 69 Principal Component Analysis: Volatile Data .................................................... 70 Cluster Analysis: Volatile Data ......................................................................... 73 Volatile Content: Similarities to Other Wine Styles ................................................. 73 5 CONCLUSION ........................................................................................................ 95 APPENDIX: VOLATILE CONCENTRATIONS .............................................................. 97 REFERENCES ............................................................................................................ 101 BIOGRAPHICAL SKETCH .......................................................................................... 107 6 LIST OF TABLES Table page 2-1 Scoring criteria used for the Blanc Du Bois session at the Florida State Fair 21st Annual Wine and Grape Juice Competition ................................................ 39 2-2 Original Davis Scorecard scoring criteria ............................................................ 40 2-3 Updated Davis Scorecard scoring criteria .......................................................... 40 3-1 Final descriptor list and corresponding training references ................................ 50 3-2 Intensity calibration references ........................................................................... 51 4-1 DA attribute intensity, chemical, and quality means with Tukey’s HSD mean separation1. Wine letter represents quality rank, with A = highest and N = lowest ................................................................................................................. 75 4-2 DA, chemical, and quality correlations significant at p < 0.10 ............................. 77 4-3 DA attribute and volatile correlations significant at p < 0.10 ............................... 79 5-1 Key for identification of volatiles used in PCA on Figure 4-9 plus Linear Retention Index values for volatiles .................................................................... 94 A-1 Concentrations of volatiles detected by GC-MS, in µg/L. Odor-active volatiles indicated by footnote .......................................................................................... 97 7 LIST OF FIGURES Figure page 2-1 Blanc Du Bois pedigree (Mortensen 1987) ......................................................... 38 2-2 The Dimensions of Wine Quality (Charters and Pettigrew 2007) ........................ 39 2-3 Monoterpene alcohols and ketones in various wines (Eggers 2005) .................. 40 3-1 Intensity rating scale used by DA panel .............................................................. 50 4-1 Quality scores of wine samples as determined by expert judging panel in decreasing order ................................................................................................. 83 4-2 Color measured by a spectrophotometer reading absorbance at the 420 nm wavelength. Samples sorted by decreasing quality score .................................. 84 4-3 TA measured in grams of tartaric acid per liter. Samples sorted by decreasing quality score ..................................................................................... 85 4-4 pH of wine samples. Samples sorted by decreasing quality score ..................... 86 4-5 Residual sugar as percent weight of wine samples. Samples sorted by decreasing quality score ....................................................................................