What You Need to Know
During fermentation, lactic acid bacteria, yeasts, and acetic acid bacteria metabolize sugars to produce ethanol, CO₂, lactic acid, and acetic acid, lowering the pH from ~6.5 to ~4.5. Proteolysis releases free amino acids that contribute to bitterness and flavor precursors, while endogenous polyphenol oxidases convert catechins to theobromine‑rich compounds, reducing astringency. If beans are prematurely heated above 60 °C, theobromine is further degraded to theophylline and caffeine.
The Science
Primary Reaction
Fermentation of sugars to acids and alcohols