Yeast population dynamics during the fermentation and biological aging of sherry wines

Molecular and physiological analyses were used to study the evolution of th e yeast population, from alcoholic fermentation to biological aging in the process of ''fino" sherry wine making, The four races of "flor" Saccharomyc es cerevisiae (beticus, cheresiensis, montuliensis, and rouxii) exhibited i dentical restriction patterns for the region spanning the internal transcri bed spacers 1 and 1 (ITS-1 and ITS-2) and the 5.8S rRNA gene, but this patt ern was different, from those exhibited by non-flor S, cerevisiae strains. This flor-specific pattern was detected only after wines were fortified, ne ver during alcoholic fermentation, and all the strains isolated from the ve lum exhibited the typical flor yeast pattern. By restriction fragment lengt h polymorphism of mitochondrial DNA and karyotyping, we showed that (i) the native strain is better adapted to fermentation conditions than commercial strains; (ii) two different populations of S, cerevisiae strains are invol ved in the process of elaboration, of fine sherry wine, one of which is res ponsible for must fermentation and the other, for wine aging: and (iii) one strain was dominant in the flor population integrating the velum from sher ry wines produced in Gonzalez Byass wineries, although other authors have d escribed a succession of Faces of flor S, cerevisiae during wine aging. Ana lyzing all these results together, we conclude that yeast population dynami cs during biological aging is a complex phenomenon and differences between yeast populations from different wineries can be observed.