Effect of additives on the rehydration ofSaccharomyces cerevisiaewine strains in active dry form: influence on viability and performance in the early fermentation phase

Abstract

The effect of five additives on the rehydration process of three commercial Saccharomyces cerevisiae wine strains, in the form of active dry yeast, was tested using the approach of design of experiments. The response to additives was monitored by observing the viability, measured using fluorescence methodology at the end of the rehydration experiments, and fermentative performance, focusing attention on the first phase of fermentation, assessed based on ethanol production and the total number of cells after 48 h from the time of inoculation in synthetic must. The results showed a correlation between viability and the presence of magnesium in the rehydration medium. However, improvement in viability was not associated with better fermentation performance, which was not affected or in some cases significantly reduced. Among the additives examined, only rehydration with inactive dry yeast and ammonium showed a positive effect on the subsequent fermentations, but not for all of the strains tested. In general, considering all of the additives tested, no relationship was found between viability at the end of rehydration and fermentation performance. These findings suggest that the viability of the rehydrated yeast cells may not be a good index of fitness in the subsequent fermentation. Copyright © 2014 The Institute of Brewing & Distilling