Influence of the Yeast Genotypes on Enological Characteristics of Sherry Wines

Abstract

The dynamics of yeast strain populations in the flor velum and certain analytical parameters of sherry wine in two "añadas", the static system for aging sherry wine in oak butts, were monitored for 12 months starting in spring 1996, in order to determine the correlations between biological and enological parameters. Metabolic characterization of yeasts from both añadas indicated the presence of <i>beticus</i> and <i>cheresiensis</i> races of <i>Saccharomyces cerevisiae</i>, although their relative proportions were different in each. The alcoholic degree, acetaldehyde content and volatile acidity level also evolved differently. The <i>cheresiensis</i> race was more predominant in the añada with the lower ethanol and acetaldehyde contents but higher volatile acidity. Molecular characterization of the strains, by karyotype and mtDNA restriction analyses, revealed a high polymorphism, with certain patterns being predominant. Greater variability was shown in the nuclear DNA than in the mtDNA due to the relatively young age of the wine. Some patterns were specific to either <i>beticus</i> or <i>cheresiensis</i> race, but several strains shared the same karyotype or mtDNA pattern, indicating similarity between the two types of strain, however, a preferential association between karyotype and mtDNA appeared. Cluster analysis of the combined patterns of karyotype and mtDNA restriction profiles distinguished three main genotypes. Patterns with higher frequencies were specific to each añada and some <i>beticus</i> and <i>cheresiensis</i> strains showed these same patterns; this was probably due to differences in the analytical conditions of each "añada" resulting in the selection of different yeast genotypes.