Winemaking is a straightforward process: yeast
ferment the sugars in grape must to produce ethanol and carbon
dioxide, along with low levels of secondary metabolites. Typically
a wine maker will begin fermentation by adding an active dry
commercial yeast to the crushed grapes. This yeast is usually Saccharomyces
cerevisiae, although some winemaking yeasts are from
the closely related Saccharomyces bayanus species. Yeast itself is a significant source of folate