Investigation of gas-producing bacteria in sufu and its effective method to control their growth

The presence of gas-producing bacteria in sufu will cause the package swelling, thus significantly affecting the storage period and sensory quality of sufu. This study aimed to isolate and identify the gas-producing bacteria in sufu and provide an effective method to control their growth. The gas-producing bacteria were isolated in sufu and identified as Weissella confusa and Weissella koreensis based on 16S rDNA. W. confusa and W. koreensis still grow and produce gas in MRS broth with a salinity of 10% oralcohol of 11% content. Nisin and Lactococcus lactis were able to inhibit the growth of W. confusa and W. koreensis, while no inhibition was observed when sodium propionate, sodium dehydroacetate, and ε-polylysine hydrochloride were used. When the salinity and alcohol content was 6%, the growth of W. confusa was inhibited at MICs of nisin of 0.250 mg mL−1 and 0.125 mg mL−1, while the growth of W. koreensis was inhibited to 0.125 mg mL−1 and 0.063 mg mL−1. Nisin and L. lactis induced changes in cell morphology by disrupting membrane integrity of gas-producing bacteria. This study guides the sufu enterprises to adopt effective measures controlling the package swelling of sufu production and extending the products' storage period.