Abstract:Pixian broad bean-chili paste (PBCP) is a traditional condiment in Southwest China, and package swelling is one of the major quality flaws in commercial PBCP. In this study, PBCP and its two semi-finished products, namely broad bean moromi (BM) and pickled chili (PC) paste were collected. Salt contents and water activities (aw) of the samples were determined and the halotolerant microorganisms were isolated. The results showed that the gas-producing samples had relatively lower salt contents and higher aw values. By inoculating the diluted sample into YM broth media containing 12% (m/m) of NaCl, Zygosaccharomyces rouxii, a halotolerant yeast, was isolated. The production of gas could be induced through inoculating the yeast in YM broth medium, or by re-inoculating the yeast in the autoclaved BM, PC and PBCP with salt contents lower than 16% (m/m). The optimal growth conditions for Z. rouxii were 4% (m/m) NaCl, pH 4~6 and 30 ℃, with the gas production being largest at 8% (m/m) NaCl and pH 5~7. Gas production by Z. rouxii was inhibited when the salt content increased in the culture medium or the sterilized samples. Z. rouxii can grow under acidic and high-salt conditions and can produce gas in PBCP, causing package swelling.
