Yeasts, or rather enzymes in yeasts, ferment liquids into alcoholic beverages. They contribute to flavor in various ways. Some maintain that yeasts in fino Sherry butts (casks) contribute to the yeasty flavor of these wines. Others see the yeasty character of Champagnes to be directly related to the long period of yeast contact that such wines have (owever, what we perceive as yeast-smells in Champagne (or similarly made sparkling wines from other countries) is more likely the result of a lightly to strongly oxidized white-grape wine blend). Many distilleries, wineries, and breweries maintain secret proprietary yeasts to ferment their products as it is one of the major contributors to flavor. When a beverage is described as yeasty, a leavened bread type of aroma is what is being referred to. (Wine,Beer,Spirits,Sake,Mead/Tasting Terms)