Evolution of Flor Yeast Population During the Biological Aging of Fino Sherry Wine

Abstract

In this study, flor yeasts which integrate the velum formed on the surface of fino sherry wines in different systems and at different steps of the biological aging have been characterized. More than 95% of the whole population belongs to <i>S. cerevisiae</i>, although four different races could be distinguished; <i>i.e., S. cerevisiae beticus</i> which is the predominant (75%), followed by <i>montuliensis</i> (15%), <i>cheresiensis</i> (5%), and <i>rouxii</i> (1%). The same distribution is found in the static and in dynamic aging systems — the <i>añadas</i> and <i>solerajes</i>, respectively. However, when studying the systems individually, variations in the frequencies of these races were found, specially with regards to <i>S. cerevisiae montuliensis</i>. These differences were due neither to the way the wine is matured nor to the geographical location, but to their physiological and metabolic characteris- tics. Thus, <i>S. cerevisiae beticus</i> which is faster at forming velum predominates in younger wines, whereas <i>S. cerevisiae montuliensis</i> which produces and resists higher acetaldehyde concentrations appears at later stages. These findings will allow the selection of the final characteristics of the Sherry wine by inoculating specific races of <i>S. cerevisiae</i>.