What You Need to Know
During fermentation, yeast metabolizes the sugars in the grape mash to produce ethanol and a mixture of organic acids, primarily citric and tartaric acids, which lower the pH to about 3.5–4.0. The addition of 1–2 % salt suppresses spoilage bacteria while encouraging yeast activity, stabilizing the process and preventing mold growth. After fermentation, the liquid is clarified by settling or filtration to remove solids and tannins, yielding a clear, acidic juice suitable as a souring agent.
The Science
Primary Reaction
Yeast fermentation of sugars to ethanol and organic acids