Definition of Term

baker’s yeast

(English) A specialized strain of Saccharomyces cerevisiae which is capable of rapid fermentative activity in bread dough, that is, under conditions of low oxygen tension, low water activity, and high osmotic pressure. The yeast is manufactured by batch culture in a medium containing molasses, vitamins, minerals and a nitrogen source for 12-18 hours at about 30°C with full aeration (to suppress fermentation). The yeast is harvested by centrifugation, washed, and concentrated by pressing or filtration. ‘Fresh yeast’ is blended, extruded, cut into cakes and wrapped; it can be stored for only a few days. ‘Active dry yeast’ is usually dried in a stream of warm air and sold as granules (water content ca. 80%). It can be stored for up to ca. 18 months in sealed containers. In aquaculture, baker’s yeast is frequently used to culture rotifers as live food for fish larvae.

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