Yeast Hybrids in Winemaking

Summary Aim: There is significant variety in the choice of commercial yeast strains available for wine production. Yeast hybrids represent one class of commercial yeasts. The purpose of this review is to define what yeast hybrids are, to describe how they arise in nature and in the laboratory, and to discuss the features of these yeasts that differentiate them from non-hybrid strains. Key Themes: How does mating occur normally in yeast? What is a hybrid yeast strain? How do hybrid strains form in nature? How are hybrid wine strains constructed in the laboratory? Are natural hybrids of wine yeast found in nature? What are the features of laboratory-generated wine yeast hybrids? What are the impacts of hybrid strains on wine composition? Impact and Significance: Yeast influence wine aroma and flavor profiles in multiple ways1. In addition to the formation of ethanol, yeast can directly produce both positive and negative aroma impact compounds, such as esters, higher alcohols, higher aldehydes, and sulfur-volatile compounds. Some yeast strains can produce factors that enhance mouthfeel, and many can modify varietal aroma through enzymatic and chemical mechanisms. Yeast mannoproteins and polysaccharides may also affect wine stability. Last, yeast end products can alter the wine matrix and therefore the sensory expression of wine characters. Yeast hybrids combine traits of Saccharomyces cerevisiae and other species in this genus, and thereby expand the metabolic repertoire of the strain. These yeasts can create novel characters in wine as well as conduct fermentation under nonstandard conditions.