Identification of Clostridium butyricum as the bacteria causing soy sauce explosion and leakage and its control using nisin

The cause of leakage and explosion of bottled soy sauce was determined by isolating gas-forming bacteria from leaking soy sauce samples, and identifying them as Clostridium butyricum. This is the first report of the isolation of C. butyricum from bottled soy sauce and identification of gas production by the bacteria as the cause of swelling and leakage in soy sauce. Their gas production was further confirmed by inoculating uncontaminated soy sauce with the C. butyricum isolated from a leaking bottle of soy sauce. The source of C. butyricum contamination could be traced back to the ingredient monosodium glutamate (MSG) with C. butyricum spores. Nisin (50 mg/L) was successfully employed to prevent C. butyricum from spoilage. The incidence of leakage of bottled soy sauce was markedly reduced after 50 mg/L nisin was added. The isolation and identification work assist food industry to control the leakage of soy sauce, and the strategy utilized in this work should assist in the characterization of spoilage organisms in other food systems.