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Am. J. Enol. Vitic. 48:1:71-74 (1997)
Copyright © 1997 by the American Society for Enology and Viticulture.
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Effects of Ethanol and Temperature on the Biological Aging of Sherry Wines

Jose Ignacio Ibeas 1, Ignacio Lozano 2, Francisco Perdigones 2, and Juan Jimenez 1

1 Unidad de Genética, Facultad de Ciencias, Universidad de Málaga, Campus Universitario de Teatinos, 29071 Málaga, Spain
2 Departamento técnico, Osborne y cia SA, Fernán Caballero, 3, Puerto de Santa María, Cádiz, Spain.

JIMMAR{at}CCUMA.UMA.ES

The film formed by flor yeasts on the surface of "fino" sherry wines was studied over a period of two years. The periodic analyses of this film indicated that temperature and ethanol strongly influenced its state. When a critical value established at 22.5°C and 15% ethanol was exceeded, the yeast layer becomes deteriorated. The deterioration of the yeast film correlated with a significant increase in the proportion of respiratory-deficient (rho-) mutants. These mutants lack the ability to form a velum, indicating that aerobic metabolism is required for flor yeasts to develop this characteristic. In addition, it suggests that the appearance of such mutants by elevated temperatures may contribute to the deterioration of the yeast layer. Once formed, the yeast film kept stable after the induction of 100% rho- cells with ethidium bromide, indicating that the velum is a long-life biological structure at temperature lower than 20°C. This result also suggests that the induction of rho- mutants by ethanol and elevated temperature is not the only mechanism leading to velum deterioration by ethanol and temperature on sherry wines.

Key words: flor yeasts, sherry wine, aerobic metabolism, rho- mutants

Submitted on May 29, 1996






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Copyright © 1997 by the American Society for Enology and Viticulture.