Metabolism of Saccharomyces cerevisiae Flor Yeasts During Fermentation and Biological Aging of Fino Sherry: By-products and Aroma Compounds

Abstract

During the biological aging of the Fino sherry, the formation of aroma compounds takes place as a result of the oxidative metabolism of the Saccharomyces cerevisiae flor yeasts, which form a film on the surface of the wine. Yeasts consume some compounds such as ethanol, glycerol, organic acids (acetic, lactic, citric and succinic), and amino acids, including proline. At the same time, yeasts produce other compounds, namely higher alcohols (isobutanol and isoamilic), acetaldehyde and acetoin. We have compared differences in aroma production according to parameters involved in winemaking such as enological techniques applied, selected yeast strains used, and length of the aging process. Fermentation of must enriched in solids and other components resulted in fino sherry with a lower volatile acidity and a higher concentration of acetaldehyde, isoamilic alcohols, and glycerol than decanted must. Furthermore, while ethanol consumption was higher in "sobretablas", other compounds, such as acetic acid or glycerol, were steadily consumed throughout the aging period. As far as the strains are concerned, S. cerevisiae (beticus) and S. cerevisiae (cheresiensis) were better at reducing the volatile acidity than S. cerevisiae ( montuliensis), which consumed more ethanol and produced more acetaldehyde (mainly responsible for the typical flavor of sherries). These results make it possible to select the final organoleptic characteristics of the wine by means of applying the appropriate enological processes and/or selected strain.