EARLY THIAMIN ASSIMILATION BY YEASTS UNDER ENOLOGICAL CONDITIONS - IMPACT ON ALCOHOLIC FERMENTATION KINETICS

The effect of early must thiamin depletion by wild yeast strains (i. e . Kloeckera and Saccharomyces species) on alcoholic fermentation kinet ics was studied. Experimental conditions affecting thiamin assimilatio n by yeasts were first determined, using factorial designs. Then seque ntial and/or mixed cultures simulating wild yeast contamination, as ob served during winemaking, were carried out in order to study the influ ence of early thiamin depletion on fermentation kinetics. The obtained results indicate that biological thiamin depletion leads to slow ferm entation and may lead to sluggish or stuck fermentation. Moreover this phenomenon is amplified in media with high assimilable nitrogen conte nts. No release of thiamin from contaminant yeast and subsequent assim ilation by fermentative yeast was observed, indicating that some enolo gical practices (such as centrifugation of musts contaminated early) m ay lead to stuck fermentation.