Stresses Imposed on Yeast During Brewing Fermentations and Their Effect on Cellular Activity

摘要

Brewer’s yeast strains are exposed to a spectrum of threats and “in-sults” that cultures encounter during wort fermentation. Culture storage (including acid washing) and their propagation can also stress yeast systems. Stresses are a plethora of parameters that a yeast culture toler-ates during its propagation, storage, and throughout and between wort fermentations. Stress can result in a number of effects on a yeast cul-ture. These include decreases in yeast viability and vitality, depletion of intracellular glycogen, increases in trehalose, and excretion of intra-cellular proteinase A and other proteinases, with effects on beer foam stability. Shear of cell wall components will also occur. In addition, modification of a culture’s flocculation characteristics can result, to-gether with the formation of unfilterable mannan-protein beer hazes. Finally, increases in respiratory deficient (petite) and other yeast mu-tants have been reported.