Gas-Producing Bacteria Causing Package Swelling in Hubei Broad Bean Paste: Isolation, Identification, and Control

The problem of swollen canned Hubei broad bean paste, a traditional fermented food, leads to significant quality degradation and economic loss. This study aimed to isolate and identify the causative gas-producing bacterium and develop an effective control strategy. A dominant strain, designated Clostridium tyrobutyricum strain LG12 (accession number MT265221.1), was isolated from swollen cans and identified via 16S rDNA sequencing. Physiological studies revealed that this isolate grew optimally at neutral-acidic pH (5-7) and exhibited high heat tolerance, surviving after 20 min of treatment at 100°C. It also showed notable salt tolerance, withstanding up to 10% NaCl. Traceability analysis confirmed that this bacterium originated from the fermented chili, a primary raw material. The efficacy of nisin, ε-polylysine hydrochloride (ε-PL HCl), and sodium diacetate in inhibiting its growth was evaluated in vitro. An optimized combination (nisin 50 mg/L, ε-PL HCl 500 mg/L, sodium diacetate 1250 mg/L) was found to inhibit bacterial growth by over 99%. Finally, this combination was validated in the Hubei broad bean paste system, where it effectively prevented package swelling, offering a practical solution for the industry.