EFFECTS OF ETHANOL, TANNIN AND FRUCTOSE ON THE SENSORY AND CHEMICAL PROPERTIES OF WASHINGTON STATE MERLOT By ANNE CAROLYN SECOR A thesis submitted in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE IN FOOD SCIENCE WASHINGTON STATE UNIVERSITY School of Food Science MAY 2012 To the Faculty of Washington State University: The members of the Committee appointed to examine the thesis of ANNE CAROLYN SECOR find it satisfactory and recommend that it be accepted. __________________________________________ Carolyn F. Ross, Ph.D., Chair __________________________________________ Charles G. Edwards, Ph.D. __________________________________________ Jeffri C. Bohlscheid, Ph.D. ii ACKNOWLEDGMENTS I would like to thank Dr. Carolyn Ross for her support throughout this project. Her advice and encouragement have been invaluable throughout this process. The other members of my graduate committee, Dr. Charles Edwards and Dr. Jeff Bohlscheid, have also been immensely helpful. Thank you to Snoqualmie Winery, for their collaboration in dealcoholizing the wine for this project. Thank you to Karen Weller, Scott Mattinson, and Jodi Anderson, for keeping me on track in all aspects of graduate life. To Medy Villamor, I am grateful for the support, the collaboration, and the endless positivity. Also, thank you to the rest of the Ross lab, for your help with sensory panels and flexibility in the lab, and to the Edwards lab, for the honorary work-space and support. Finally, this project would not have been possible without the support of my parents, William and Tammi Secor; my fiancé, Brandon Zwink; and my dearest friends. Thank you. iii EFFECTS OF ETHANOL, TANNIN AND FRUCTOSE ON THE SENSORY AND CHEMICAL PROPERTIES OF WASHINGTON STATE MERLOT ABSTRACT By Anne Carolyn Secor, M.S. Washington State University May 2012 Chair: Carolyn F. Ross The relationship between matrix components and sensory properties of red wine was examined. A Washington State Merlot was dealcoholized to 3.2% and alcohol was added back to four ethanol levels: 3.2%, 8%, 12% and 16% ethanol (v/v). Within each treatment, wines were maintained at the original tannin (211 mg/L CE tannin) and fructose (120 mg/L fructose), or brought to 1500 mg/L CE tannin and/or 2000 mg/L fructose (n=16 solutions). The wines were spiked with the same concentrations of three aroma compounds: 3-methyl-1-butanol, 2- phenylethanol, and eugenol. These wines were then evaluated by a trained panel (n=10) for the intensity of aromas and flavors (‘caramel’, ‘rose’ and ‘clove’), tastes (‘bitterness’ and ‘sourness’), and mouthfeel (‘astringency’ and ‘heat’). Gas chromatography/mass spectrometry was used to quantify aroma compounds. PCA was used for correlation between sensory and analytical results. All data were analyzed using analysis of variance (p<0.05) and Fisher’s Least Significant Difference. Analytical results showed that ethanol significantly reduced the relative headspace recovery of all three compounds. The interaction effects between ethanol, tannin and fructose varied based upon the aroma compound and the ethanol content. In standard red wine ethanol concentrations (12 to 16%), volatile recovery was not influenced by tannin or fructose. iv However, in low ethanol wines, high tannin concentration negatively impacted the relative recovery of 3-methyl-1-butanol, 2-phenylethanol, and eugenol. An increase in fructose concentration when ethanol and tannin concentrations were low reduced the recovery of 3- methyl-1-butanol, but increased the recovery of 2-phenylethanol. The trained panel sensory evaluation results showed that increasing ethanol concentrations increased ‘clove’ flavor, and ‘heat’, and decreased ‘sourness’ intensity. High fructose concentration increased ‘rose’ aroma and flavor scores, and decreased ‘clove’ aroma scores. Tannin concentration positively affected ‘clove’ flavor while perceived ‘drying’ and ‘bitterness’ were impacted by ethanol*tannin. PCA separated treatments based on ethanol, tannin, and fructose concentrations, and chemical analyses of aroma compounds were not correlated with perceived aromas or flavors. This study demonstrated the complexity of relationships within the wine matrix, indicating chemical and sensory effects that winemaking techniques such as saigneé, the addition of water, and dealcoholization may have on wine quality. v TABLE OF CONTENTS Page ACKNOWLEDGMENTS ............................................................................................................. iii ABSTRACT ................................................................................................................................... iv LIST OF TABLES ....................................................................................................................... viii LIST OF FIGURES ........................................................................................................................ x CHAPTER I: INTRODUCTION .................................................................................................... 1 CHAPTER II: LITERATURE REVIEW ....................................................................................... 4 Importance of Wine to Washington State ................................................................................. 4 Current Trends in Increasing Alcohol Content in Wines .......................................................... 4 Methods of Alcohol Reduction ................................................................................................. 6 Saigneé and water addition ................................................................................................. 6 Dealcoholization by reverse osmosis .................................................................................. 7 Wine Sensory Attributes ........................................................................................................... 8 Alcohol burn ....................................................................................................................... 8 Astringency ......................................................................................................................... 9 Sourness ............................................................................................................................ 10 Bitterness ........................................................................................................................... 11 Aromas .............................................................................................................................. 13 Flavors............................................................................................................................... 16 Physiological factors ......................................................................................................... 17 Wine Matrix: Volatile and Non-Volatile Components ........................................................... 18 Tannin ............................................................................................................................... 19 Fructose ............................................................................................................................. 21 vi Ethanol .............................................................................................................................. 21 Aromatic volatile compounds ........................................................................................... 22 Interactions between pairs of components ........................................................................ 25 Interactions among three or more components ................................................................. 27 CHAPTER III: MATERIALS AND METHODS ........................................................................ 31 Materials ................................................................................................................................. 31 Base Wine ............................................................................................................................... 31 Volatile Compound Profiling .................................................................................................. 33 Calibration Curves .................................................................................................................. 34 Wine Treatments ..................................................................................................................... 35 Chemical and Volatile Analysis .............................................................................................. 37 Sensory Analysis ..................................................................................................................... 37 Data Analysis .......................................................................................................................... 41 CHAPTER IV: RESULTS AND DISCUSSION ......................................................................... 42 Chemical Analysis .................................................................................................................. 42 Volatile Compound Analysis .................................................................................................. 45 Sensory Evaluation ................................................................................................................. 57 Principal Component Analysis and Pearson Correlation .......................................................