Mechanical dispersion procedures improve the rehydration of active dry yeast

The process of reactivating the yeast preparation and inoculating it into the must constitutes a critical stage in the management of alcoholic fermentation. Various parameters condition the efficiency of active dry yeast (ADY) reactivation for oenological use: temperature, composition of the medium (concentration of sugar and assimilable nitrogen), the way of dispersion in water and associated hydration times. This paper reports the results of experiments aimed at evaluating the effects of mode of dispersion in water (38 degrees C) and of rehydration timing on the recovery of ADY vitality during the reactivation stage. The experimentation, carried out on a broad statistical basis, made it possible to determine that the currently suggested rehydration stage carried out with pre-soaking as presently envisaged in standard protocols, does not improve the vitality of the preparation, while efficient stirring of the preparation during the rehydration stage leads to a higher recovery of the vitality of the ADY with optimization of the procedure with reactivation times of 120 min. (c) 2006 Elsevier Inc. All rights reserved.