Isolation and characterization of yeast strains with ability to decrease volatile acidity of wines

Abstract

The level of acetic acid, the main component of volatile acidity, is critical for wine quality. Its concentration in wines is approximately 0.5 g/L and, legally, must remain below 1.0g/L. Winemakers use a procedure called “remostagem” to lower acetic acid of wines with high volatile acidity (above 0.8g/L). The spoiled wine is mixed with freshly crushed grapes (1) in a proportion of no more than 20-30% (v/v). The volatile acidity of this mixture and of the newly made wine should not exceed 0.6 and 0.3 g/L, respectively. The aim of this study is to select wine yeasts capable of decreasing the volatile acidity of spoiled wines. First, from 135 isolates colleted during a “remostagem” procedure, 4 wild yeasts were selected based on their ability to consume acetic acid in the presence of glucose at pH 4,0 or 6,0. The 4 strains were further analyzed regarding simultaneous acetic acid and glucose consumption, specific growth rate and ethanol production in comparison to the commercial strain Lalvin QA23, Saccharomyces cerevisiae IGC 4072 and Zygosaccharomyces bailii ISA 1307, using minimal media containing acetic acid (0.5%, v/v) and glucose (0.5%, w/v) at 25ºC and pH 3,0. Although less efficiently than Z. bailii the 4 isolated strains were able to use acetic acid in the presence of glucose. Their potential application in the deacidification of acidic wines is being studied.