Effect of Native Yeasts and Selected Strains ofSaccharomyces cerevisiaeon Glycosyl Glucose, Potential Volatile Terpenes, and Selected Aglycones of White Riesling (Vitis viniferaL.) Wines

Four strains ofSaccharomyces cerevisiaeand native yeasts were evaluated for their influence on White Riesling-conjugated aroma precursors, which were measured using three analytical procedures. Fermentation resulted in a decrease in glycosyl glucose with the greatest reduction occurring with native yeast fermentations. Potentially volatile terpene levels were similar among wines following fermentation, the exceptions being those fermented using the Fermiblanc strain and native yeasts which showed lower concentrations. Storing wines for 45 days on the yeast lees (sur lie) reduced the glycosyl glucose and potential volatile terpene content with slight differences among treatments. Gas chromatographic analysis of selected glycosidically bound monoterpene alcohols, oxides, and aromatic alcohols showed a trend similar to the glycosyl glucose and potentially volatile terpenes following fermentation. Fermentation had a variable effect on the free linalool concentration. Levels of nerol and geraniol decreased while free α-terpeniol, hotrienol, furanic and pyranic linalool oxides, benzyl alcohol, and 2-phenylethanol increased. The concentrations of free volatiles following fermentation differed among yeasts, but differences were below the sensory thresholds reported for each compound.