What You Need to Know
During long proofing, yeast metabolizes sugars (maltose, dextrins, and added sugars) to CO₂ and ethanol, while amylases hydrolyze starch into fermentable sugars that further feed the yeast. Lactic acid bacteria from sourdough starters lower the pH to ~4.5, strengthening the gluten network and enhancing crumb texture. The extended fermentation also releases free amino acids that participate in Maillard reactions during baking, producing complex browning and flavor compounds.
The Science
Primary Reaction
Yeast fermentation of sugars to CO₂ and ethanol; amylase hydrolysis of starch to sugars; lactic acid bacteria fermentation of sugars to lactic acid