Influence of the yeast genotypes on enological characteristics of sherry wines

The dynamics of yeast strain populations in the flor velum and certain anal ytical parameters of sherry wine in two "anadas", the static system for agi ng sherry wine in oak butts, were monitored for 12 months starting in sprin g 1996, in order to determine the correlations between biological and enolo gical parameters. Metabolic characterization of yeasts from both anadas ind icated the presence of beticus and cheresiensis races of Saccharomyces cere visiae, although their relative proportions were different in each. The alc oholic degree, acetaldehyde content and volatile acidity level also evolved differently. The cheresiensis race was more predominant in the anada with the lower ethanol and acetaldehyde contents but higher volatile acidity. Mo lecular characterization of the strains, by karyotype and mtDNA restriction analyses, revealed a high polymorphism, with certain patterns being predom inant. Greater variability was shown in the nuclear DNA than in the mtDNA d ue to the relatively young age of the wine. Some patterns were specific to either beticus or cheresiensis race, but several strains shared the same ka ryotype or mtDNA pattern, indicating similarity between the two types of st rain, however, a preferential association between karyotype and mtDNA appea red. Cluster analysis of the combined patterns of karyotype and mtDNA restr iction profiles distinguished three main genotypes. Patterns with higher fr equencies were specific to each anada and some beticus and cheresiensis str ains showed these same patterns; this was probably due to differences in th e analytical conditions of each "anada" resulting in the selection of diffe rent yeast genotypes.