郫县豆瓣是我国西南地区的传统调味品，胀包是市售郫县豆瓣最主要的质量缺陷。该研究采集了郫县豆瓣和其两种半成品，甜瓣子和辣椒醅，测定了其食盐含量和水分活度（Water Activities，aw)，并筛选了其中的耐盐微生物。结果表明，产气的样品食盐含量相对较低，aw相对较高。将样品稀释液接种于含12%（m/m）氯化钠的YM肉汤培养基中，可分离出一种耐盐微生物，鲁氏接合酵母（Zygosaccharomyces rouxii）。鲁氏接合酵母在YM肉汤培养基，或者回接入食盐含量低于16%（m/m）的灭菌甜瓣子、辣椒醅和郫县豆瓣中，均可导致产气现象发生。其最适生长条件为含盐量4%（m/m），pH值4~6及30 ℃。其在含盐量8%（m/m）、pH值5~7的情况下产气量最大。提高培养基或灭菌样品的盐含量，鲁氏接合酵母的产气受抑。鲁氏接合酵母可在酸性高盐条件下生长，并能够在郫县豆瓣样品中代谢产气，导致其胀包。

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.

国家重点研发计划项目（2016YFD0400505）；成都市科技计划项目（2018-YF09-00036-SN）