Sensory and chemical evaluation of riesling, chardonnay and pinot noir fermented by different strains of Saccharomyces cerevisiae

Graduation date: 1995Fermentation of the grape must into wine is one of the most important steps\ud in winemaking. Selected yeast strains of Saccharomyces cerevisiae have\ud been used for many years to ensure complete and even fermentations. The\ud formation of volatile compounds also occurs during fermentation and will\ud influence the sensory perception of the wine. The main objective of the\ud research was to study the sensory and chemical composition of 1992 Oregon\ud Riesling, Chardonnay and Pinot Noir wines fermented with different\ud commercial S.cerevisiae strains.\ud In the first study, Free-Choice Profiling was used to study the sensory\ud profiles of all three varieties after 7 and 20 months of aging. This method was\ud used in order to utilize a panel of expert winemakers for the tastings. The\ud sensory data analyzed through Generalized Procrustes Analysis showed that\ud some strains were similar while others were different in terms of aroma and\ud flavor at 7 months of age. After 20 months of aging, differences and\ud similarities were still present although the sensory profiles were different from the young wines. This last finding showed that differences are still present\ud after a period of aging.\ud In the second study, the chemical composition of all three varieties and the\ud volatile composition of selected wines of Riesling and Chardonnay were\ud studied. In both white varieties, statistical differences in titratable acidity,\ud residual sugar, volatile acidity and malate content resulted from fermentation\ud with different yeast strains. The volatile composition was qualitatively similar,\ud but some quantitative differences, as relative concentration, were found.\ud Whether or not those differences had a sensory impact was not investigated.\ud Results of the present study showed the need for further studies in order to\ud understand the role of yeast in flavor development. Relationships between\ud sensory profiles and volatile composition could help winemakers to\ud understand the influence of a selected strain on a particular variety and to\ud select yeast strains to optimize wine quality