Sensory analysis, grape glycosides

Williams, P.J. and Francis, I.L. (1996) Sensory analysis and quantitative determination of grape glycosides—the contribution of these data to winemaking and viticulture, in G.R. Takeoka, R. Teranishi, P.J. Williams, and A. Kobayashi, (Eds) Biotechnology for improved foods and flavors, ACS Symposium Series 637, Am. Chem. Soc., Washington DC. 

Sensory Analysis and Quantitative Determination of Grape Glycosides... 

The sensory analysis of products releasd by hydrolysis of grape glycosides is a most important aspect of precursor research, yet the subject is relatively neglected in comparison to the work that has been devoted to the chemical analysis of both aglycones and glycosides. 

The first five chapters of this book focus on the grape derived and varietal flavors of wines. Many of these compounds occur as nonvolatile glycosidic flavor precursors and the separation and analysis of these precursors have been a challenging and active field of research. The isolation and quantification of trace volatiles represent examples of the difficulties faced by flavor chemists as they attempt to characterize varietal flavors with sensory thresholds in the parts per trillion range and lower. 

New developments in glycoside research of grapes and wines are a) the use of formal sensory descriptive analysis to investigate the precise role of glycosides in flavor expression, and b) the possibility of grape and wine quality evaluation through the quantification of glycosides. These developments are discussed here. 

The aroma properties of hydrolyzed glycosides from Semilion, Sauvignon Blanc and Chardonnay juices have been investigated using sensory descriptive analysis. Commercial wines were available for two of the varieties of the study, i.e. Chardonnay and Semilion, and descriptive analysis of these demonstrated that some aroma attributes characterizing the wines were also aromas perceived in the hydrolyzed precursors. Thus, it was inferred that the grape precursors, on hydrolysis, contribute to and enhance key aromas of the wines (Francis et al. 1992). 

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