The Maillard Reaction: Crust Browning Chemistry

Reducing sugars: Amylases degrade starch to dextrins and maltose. Commercial yeast bread accumulates 0.3–0.5% maltose (dry weight). Sourdough: 1–2%. Yeasts consume some, but not all.
Free amino acids: Proteases are 2–3× more active at pH 4.2–4.5 than at pH 5.5. After 24 hours: sourdough contains 150–300 mg free amino acids per kg flour vs. 50–100 mg in commercial yeast bread. Lysine—the best Maillard partner—is significantly elevated.
Flavor precursors: Sourdough fermentation also produces acetaldehyde, ethanol, diacetyl, and acetic acid—all participants in the final flavor bouquet.

Golden brown sourdough crust with intricate scoring patterns

Chemistry Crust Science ~9 min read April 29, 2026

Oren Kmelgren
Certified Baker, I.N.B.P. Rouen, France
Founder, Water & Flour Workshops, Tel Aviv
20 years professional baking experience
waterandflour.co.il

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