What did Grain-Based Alcoholic Fermentation look like?

Grains + qu + water → placed in sealed or semi-sealed vessels → after a period of time, the liquid is filtered out → the wine is ready.

How did Grain-Based Alcoholic Fermentation work?

Molds in qu secrete amylase → hydrolyze starch to glucose (saccharification) → yeast converts glucose to ethanol + CO₂ (alcoholic fermentation) → both processes occur simultaneously in the same vessel → parallel fermentation.

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曲蘖酿酒

Grain-Based Alcoholic Fermentation

The parallel fermentation technique that defines all traditional Chinese grain-based alcohol: using qu (曲) as a combined saccharification-and-fermentation starter to convert starch directly to ethanol in a single vessel — eliminating the separate malting step required by Western brewing.

曲蘖酿酒

Scientific Principle

Parallel fermentation (复式发酵): Starch (C₆H₁₀O₅)n → glucose (C₆H₁₂O₆) → 2C₂H₅OH + 2CO₂. Unlike Western brewing which separates saccharification (malting) from fermentation, the qu system runs both processes simultaneously in one vessel — Aspergillus molds continuously hydrolyze starch while Saccharomyces yeasts convert the resulting sugars to ethanol. This co-fermentation is thermodynamically advantageous because yeast rapidly consumes glucose, pulling the amylase-catalyzed hydrolysis forward (Le Chatelier's principle). The result is higher ethanol yield from the same grain input. Modern industrial SSF (simultaneous saccharification and fermentation) for bioethanol is a direct descendant of this ancient Chinese innovation.