Special Purpose Wine Yeasts

Selecting a yeast strain is one of the most consequential decisions a home winemaker can undertake. Yeast suppliers provide tables and charts of characteristics like alcohol tolerance, influence on varietal character, speed of fermentation, suitable temperature range, nitrogen nutritional needs, and other variables. Among the routine yeast choices, though, are also found yeasts that have been selected and grown to address very specific conditions or problems. When a winemaker anticipates such a situation, that special purpose may override ordinary yeast selection considerations. Conditions like the risk of hydrogen sulfide (rotten egg stink) development, enhancing aromas, tolerating high alcohol, helping assure malolactic fermentation success, or even completing part of the malolactic conversion through yeast metabolism can shape the selection process. While there is academic research on genetic modification of yeast strains for specific purposes, genetically modified organisms (GMOs) do not have good market acceptance among winemakers. Consequently, all of the strains discussed here are either selected from nature or hybridized from natural stocks through conventional breeding techniques. Sulfur-Specific Yeast Some yeast strains and some grape varieties have long been viewed as