Improving alcoholic fermentation by activation of Saccharomyces species during the rehydration stage

The rehydration of selected active dry yeasts is essential for improving control of the wine fermentation process. To help yeast cells withstand the extreme conditions to which they are subjected during rehydration, winemakers often add adjuvants directly to the must. However, few commercial activators are added directly to the yeast rehydration water, even though this might render hydration more efficient due to a favourable osmotic gradient.The present study examined the effect of nine “activators” added directly to the water to rehydrate four commercial wine yeast strains by measuring the vitality, viability and metabolic activity of the process, plus residual sugars, glycerol and ethanol levels at days 2, 8 and 15. The fermentation kinetics were monitored and data were adjusted to a modified Gompertz equation.The activators, some of which had hitherto rarely been tested in combination with Saccharomyces, were selected for their potential activity and ability to enhance processes and/or improve cell structures. Semi-quantitative results revealed that the four wine yeasts responded very differently to the activators, indicating a high degree of strain specificity. There appeared to be no “universal activator”, indicating that a “tailor-made” activator will likely need to be formulated for each commercial yeast strain.

► Certain molecules/ions increases residual vitality of the wine strains. ► Some supplements improved their metabolic activity and kinetic profile. ► Wine yeasts tested showed a high degree of strain-specificity-activator effect. ► It is adequate to speak about yeasts rehydrated with activators tailored specifically.