Anne Flesch and Etienne Dorignac*
*Fermentis, 137 rue Gabriel Peri, 59170 Marcq-en-baroeul, France (e.dorignac@fermentis.lesaffre.com)

Due to the biologically unfavorable nature of a base wine intended to undergo a Charmat method, the pitching yeast should have optimal viability and be acclimatized to wine conditions prior to inoculation. Three different strains were propagated using two methods. The “direct rehydration” method consisted of simple rehydration of the yeast in a diluted base wine. The “gradual acclimatization” method was multi-stage to acclimatize the yeast to both wine conditions and cooler temperatures through multiple sub-culturing steps. Pitching was determined by cell density. Each strain responded differently to the “direct” preparation method and had optimal viability at different times throughout the procedure. Two strains grew fast and showed their greatest viability early in propagation and before maximum cell counts. They failed to start the subsequent secondary fermentation, suggesting that cell counts alone are not optimal to determine the pitching time. Using the “acclimatization” method, these strains behaved similarly during propagation, but differently at pitching, one being much more affected by wine conditions, but both succeeding to achieve the secondary fermentation. Greater viability of the starting yeast culture not only reduces the risk of failed secondary fermentation, but also decreases the chance that undesirable “off-flavors” are produced, such as indole, which is known to impart plastic aromas. Indole is produced by yeast through metabolism of tryptophan and its production could be linked to sub-optimal yeast vitality that can occur during sparkling wine pro- duction. Using the “acclimatization” method, the three strains were used to carry out secondary fermentation in a tryptophan-supplemented base wine. Only one strain, interestingly not showing the lowest viability, produced indole. This suggests that while culture vitality may contribute to indole production, there may also be predispositions in some yeast strains that increase their indole production potential.

Funding Support: Lesaffre-Fermentis