Cultured yeast characteristics

Yeast are cultured in large sterile tanks with vigorous aeration under conditions which encourage biomass but discourage alcohol formation. They are then filtered, washed, dried, and packed in sterile containers, often under vacuum, for transfer to the winery (or brewery or bakery). Well over one hundred different strains are now produced worldwide as active dried wine yeast preparations. Active dried yeast is quickly and simply reactivated with warm water or diluted grape juice at 40 °C/104 °F for 15 minutes. Some wineries culture their favoured yeast in grape juice with or without vigorous aeration and add about 2–4% by volume to the juice or must to initiate fermentation. Following use in winemaking, the yeast and grape debris are freed of as much wine as possible and usually discarded. A minor proportion may be processed to recover alcohol, tartrates, and occasionally grapeseed oil.