Wine yeasts

Yeasts used for the fermentation of grape musts to produce wines, which may be spontaneously occurring wild yeasts or pure cultured strains. They are mainly Saccharomyces species, chiefly S. cerevisiae, although other genera may play a role in the early stages of fermentation before alcohol levels rise. Different strains shape aroma, fermentation speed, alcohol tolerance, and the production of flavour compounds, so winemakers select them for the style they want, from crisp whites to robust reds. Some strains secrete protein or glycoprotein killer toxins able to destroy sensitive yeast strains, which may be disadvantageous if desirable strains are killed or beneficial if contaminating wild yeasts are eliminated. Reliable fermentation is the winemaker’s first quality requirement.