Fermentation characteristics of dried brewers yeast: Effect of drying on flocculation and fermentation

Strains of freshly propagated ale and lager yeast were compared with identical dried strains during wort fermentations. While several factors remained within standard expectations and were favorably matched to freshly propagated yeast fermentation results, a number of undesirable characteristics were associated with the dried yeast brews, especially reduced viability. The Helm flocculation test and static fermentations showed that flocculation is affected by the drying process, especially with lager strains. Also, dried yeast seems to induce a greater amount of haze in suspension, and the fermentation has a considerably less stable foam than fermentations with the fresh yeast samples, which may be due to the increased levels of extracellular proteinase found. It is suggested that many of the effects observed are a result of pitching high levels of dead yeast into the wort and that this could be alleviated by increasing the viability of the dried yeast, possibly by propagating on carbon sources such as maltose to increase levels of trehalose, a reported stress protectant.