Overview
Low-Temperature Daqu is a specialized fermentation starter central to traditional Chinese baijiu production, particularly for light-aroma (qingxiang) varieties. Unlike medium/high-temperature Daqu used for strong-aroma baijiu, it is fermented at 40-50°C, yielding a distinct microbial profile dominated by Saccharomyces and Rhizopus species. Historically developed in Shanxi Province, this Daqu type enables cleaner, fruitier aromas in the final liquor. Its production follows seasonal cycles, with quality dependent on raw material selection (wheat:barley ratios), fermentation duration (typically 30-45 days), and post-fermentation aging (3-6 months).
Physical and Chemical Properties
Low-Temperature Daqu exhibits porous, irregular blocks with visible microbial colonies. Its enzymatic activity includes high α-amylase (800-1,200 U/g) and glucoamylase (300-500 U/g) concentrations, crucial for starch conversion during brewing. The pH ranges from 6.0-6.8, with moisture content strictly controlled below 12% post-drying. Volatile compounds include ethyl acetate (fruity notes) and ethyl lactate, though at lower concentrations than high-temperature Daqu. Its microbial diversity (10⁶-10⁸ CFU/g) is carefully balanced to prevent off-flavors.
Main Applications
Primarily used for light-aroma baijiu like Fenjiu, this Daqu initiates simultaneous saccharification and fermentation (SSF) in solid-state brewing. It contributes to: (1) Efficient starch conversion through enzymatic action, (2) Production of ethyl acetate and other esters for floral/fruity aromas, and (3) Controlled fermentation temperatures (18-22°C) to preserve delicate flavors. Some producers blend it with medium-temperature Daqu for strong-aroma baijiu to enhance complexity. Modern applications include experimental use in craft rice wines and vinegar production, leveraging its stable microbial consortium.
Safety and Storage
While biologically active, Low-Temperature Daqu poses minimal safety risks when handled properly. Key precautions include: wearing dust masks during processing (to avoid respiratory irritation from spores), and using dry, sanitized tools to prevent cross-contamination. Optimal storage requires breathable packaging (traditional straw mats or modern perforated bags) in humidity-controlled warehouses (<70% RH). Shelf life is 6-12 months, with periodic quality checks for mold overgrowth or moisture absorption. Discard if black/green mold appears excessively.
B2B Procurement Guide
Industrial buyers should prioritize: (1) Supplier audits to verify traditional production methods (e.g., natural inoculation vs. artificial additives), (2) Laboratory testing for microbial counts (minimum 10⁶ CFU/g viable yeasts) and enzymatic activity, and (3) Batch-to-batch consistency in sensory evaluation (earthy, wheaty aroma without mustiness). Bulk pricing negotiates at 10+ ton quantities, with discounts for multi-year contracts. Regional differences exist—Shanxi-produced Daqu commands 10-15% premiums. Transportation must avoid high temperatures (>30°C) to preserve microbial viability. Sample testing in small-scale fermentation is strongly advised before large purchases.
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