By John Brennan Updated Mar 24, 2022
Maintaining stable pH or hydrogen‑ion concentration is critical for yeast performance. Yeast are living cells whose biochemistry operates optimally within a narrow pH window (typically 4.0–6.0). Outside this range, growth slows or cells die.
During alcoholic fermentation yeast convert sugars into ethanol and CO₂. The released CO₂ is the same gas that makes bread dough rise – it forms bubbles that expand the dough.
CO₂ dissolves in the fermentation broth, reacting with water to form carbonic acid. The resulting acidification can lower the pH below the yeast’s optimal range, inhibiting activity. Buffers are therefore added to neutralize excess acid.
Buffer compounds “soak up” excess protons or hydroxide ions, keeping the pH change minimal until the buffer capacity is exhausted. This stability ensures consistent yeast metabolism and high product yield.
