Modulation of grape must vitamin content by oenological treatments affects Saccharomyces cerevisiae fermentation...

This study explores the impact of oenological treatments with fining agents or yeast-based nutrients on the vitamin content of grape musts, and thus on the fermentative performance of Saccharomyces cerevisiae yeasts and the volatile composition of wine. Products such as bentonites and oenological carbons were shown to deplete several B-group vitamins from the must, while yeast derivatives were able to release significant amounts. Bentonite was used to modulate the vitamin B₁ (thiamine) content of a real must and different yeast inoculation procedures were evaluated: active dry yeast and cells precultivated in order to modulate their physiological state and intracellular B₁ pool. A significant impact of initial thiamine on fermentative activity was observed, while the effect of inoculation seemed to be linked to the adaptation of yeasts to liquid medium rather than intracellular B₁. Thiamine availability was linked to an overall increase in volatile compound production. B₁ addition to a bentonite treated must restored the volatile profile of the untreated control, suggesting that thiamine depletion is a major factor underlying the effects of bentonite treatment on wine volatile composition. These results allowed to identify the mechanisms by which fining agents can modify wine characteristics while confirming thiamine's importance in vinification processes.