DYNAMICS OF FLOR YEAST POPULATIONS DURING THE BIOLOGICAL AGING OF SHERRY WINES

Molecular and physiological analyses were applied for the study of fil m-forming yeasts (flor yeasts) over the period of two years in sherry wines. According to the molecular criteria used for distinguishing flo r yeasts, six different strains were identified. Some of these strains , which differed in their molecular karyotype, yielded identical mitoc hondrial DNA restriction patterns, and some others showing distinguish able mitochondrial genomes exhibited identical karyotype, suggesting t hat the different flor yeast strains identified are closely related. B y means of these molecular techniques, a single and stable strain was usually identified in the yeast film of individual barrels; this strai n may, however, vary in different barrels. According to physiological properties two main types of flor yeasts were identified, one overprod ucing acetaldehyde and a second type (dominant strain) showing a high rate of film formation. These two properties might influence the yeast ecology in sherry wines, being the rate of film formation the main fa ctor driving the dynamic of flor yeast populations.