Biogenic Amines Control in Bacterial‐Type Douchi Using Bacillus velezensis A1: Strain Screening, Process Optimization, and Industrial Validation

The study focused on biogenic amines (BAs) in fermented products, particularly douchi. Three strains showing high protease activity (> 90.00 U/mL) and low BA levels (< 40 mg/kg) were isolated from naturally fermented douchi: A1 Bacillus velezensis , A2 B. glycinifermentans , and A3 B. subtilis . A1, with the lowest total biogenic amine (TBA) levels, was selected as the representative strain. The optimal fermentation conditions (8% inoculum, 37°C temperature, 3 days duration) reduced TBA to levels well below the FDA standard (< 1000 mg/kg). Compared to the natural fermentation (NF), it was verified that the TBA of douchi was lowered to 10.51 ± 0.21 mg/kg after optimized fermentation, approximately reduced 10.80‐fold. Spermine levels decreased by 43.17‐fold, followed by tyramine and phenethylamine. Further, apply them to large‐scale cultivation (scaled up by 100‐fold) in actual production during colony‐enhanced fermentation (CEF). The physicochemical properties and BA levels were monitored to assess the correlation. The findings showed that the douchi of CEF had up to 0.94% amino acid nitrogen (≥ 0.25% EN) and 0.72% total acid (≤ 2.5% EN). The TBA level was only 38.27 ± 0.13 mg/kg, significantly lower than NF (94.94 ± 2.59 mg/kg). This study proposed BA‐reducing methods through strain screening and process optimization, particularly achieving large‐scale verification from the laboratory to the factory. This approach significantly reduced the TBA levels in bacteria‐type douchi, offering a crucial reference for the industrial‐scale safe production of fermented soybean products.

Practical Applications

This research offers industrial‐level guidance for douchi production. By utilizing Bacillus velezensis A1 and optimizing the process, the TBA can be reduced by a factor of 2.5 while maintaining product quality (T/GZSX 014–2018). This approach provides a collection of directly applicable safety production technology models for fermented soybean product enterprises, thereby assisting the industry in improving product safety and addressing health consumption demands.