The use of active dry yeast has been widely accepted in the brewing industry as both quality and diversity have been improved considerably in the last decade. In short, the production of active dry yeast starts from a vial with pure liquid culture followed by a series of propagation steps in aerobic fermenters of increasing volume. In the final production fermenter the yeast is grown aerobically. Next the yeast is harvested by centrifugation, concentrated to about 32% dry matter by rotating vacuum filters and dried in a so called fluidized bed dryer in which fast, homogeneous and protective drying is guaranteed. To permit a good resistance to rehydration, the yeast is coated with a protective agent (most times the vegetal emulsifier sorbitan monostearate (MSS)) just prior to drying.

The final powder (see figure 1) consists of 94-97% dry matter and is vacuum-packed to protect against oxidation and moisture and allows preservation of up to 3 years. The long shelf life is one of the major advantages of active dry yeast. In addition, when considering production management there are several other advantages of active dry yeast as a replacement of liquid yeast propagation like e.g. significantly lower costs, no need for yeast quality management (done by supplier) and a massive increase in production flexibility. In comparison with yeast propagation, the preparation time of active dry yeast can almost be neglected. The statement (still circulating on the internet) that propagated yeast has a better fermentation performance and yields better quality beer than active dry yeast has been disproven in several academic studies. Actually, the fermentation and drying processes and related recipes have been designed to best shape-up the yeast in terms of vitality, viability and purity at time of rehydration and fermentation start. Nowadays many high quality and award winning beers are being produced with active dried yeast.