2.2.2 Physiology and Morphology of Yeast
There are over 100 genera of yeast, representing around 700 species (Swiegers et al., 2005), but a limited number are used in the production of beverages. In a winemaking context, for example, there may be up to 16 species involved, of which only one (S. cerevisiae) is of any real significance. Despite the considerable phenotypic differences among the yeast strains used for commercial brewing and winemaking purposes, most of them are now considered to be physiological strains of S. cerevisiae. The assignment of most of the traditional wine yeast strains to a single species does not, however, imply that all strains of S. cerevisiae are equally suitable for the various wine fermentations; they differ significantly in their fermentation performance and their contribution to the final bouquet and quality of wine and distillates (Pretorius, 2000).