【作者】 李娜；

【导师】 罗立新；

【作者基本信息】 华南理工大学 ， 微生物学， 2015， 硕士

【摘要】 酱油是我国历史悠久的酿造型调味食品,深受广大人民欢迎。随着对酱油探究的逐步深入,发现酱油对人体具有保健作用,而良好的酱油品质是发挥其保健作用的基础。若酱油发生胀气、胀罐等现象,不仅影响产品外观,而且会降低酱油的品质。研究发现,酱油胀气、胀罐现象的发生与微生物活动密切相关。因此,本论文从酱油成品与酱醅的基本理化性质,以及酱油中微生物组成两方面入手,对三个不同产地的酱油进行分析,试图阐释酱油发生胀罐、胀气的原因。主要的研究方法与成果如下:⑴运用生化检测手段与HPLC技术研究了同批次正常成品酱油与胀罐酱油的基本理化性质,包括酱油的p H值、总酸度、含盐量、还原糖、乳酸与乙酸等。实验结果表明酱油样品中乙酸含量差异较小,且含盐量在标准范围16%~18%之内。胀罐酱油中乳酸含量均高于正常酱油,而还原糖含量却低于正常酱油。说明胀罐酱油的部分理化性质发生了改变。⑵运用传统的平板培养与巢式PCR-DGGE技术研究了胀罐酱油与正常酱油中主要污染菌的差异。实验结果表明:平板培养筛选到4株菌(Bacillus subtilis,Lactobacillus acidipiscis,B.oleronius和B.flexus);巢式PCR-DGGE方法鉴定到4株菌(L.piscium,L.pobuzihii,L.acidipiscis和Lactobacillus sp.);两种方法均能鉴定到L.acidipiscis菌株。正常酱油中主要污染菌为B.subtilis,B.oleronius,L.piscium和L.pobuzihii;胀罐酱油中主要污染菌为B.subtilis,B.oleronius,B.flexus,L.piscium,L.pobuzihii,L.acidipiscis和Lactobacillus sp..可看出胀罐成品酱油中污染菌多于正常酱油,而腐败酱油的理化性质改变可能与其中的微生物生长代谢相关。⑶为了筛选到产气能力较强的菌株,本研究从酱醅中筛选到2株新的微生物菌株(Enterobacter aerogenes,Enterococcus faecium),其中E.aerogenes产气能力很强。将(E.aerogenes,E.faecium,L.acidipiscis)三株产气菌接种到成品酱油中,发现酱油p H值会发生微弱改变;并且这三株菌对温度、p H值、盐度均有一定程度的耐受性。说明酱醅中污染微生物若灭菌不彻底,遗留在酱油成品中,会导致酱油胀气腐败。这三株菌的分离鉴定,对酱油的质量保证和食用安全性具有重要意义。通过以上研究,我们初步探究了胀罐酱油发生腐败的原因,为酱油生产与保藏提供了实验与技术支持。更多还原

【Abstract】 Soy sauce(Jiang you) have been consumed for centuries as acondiment in China. Nowadays, soy sauces are the subject of worldwide interest. Soy sauce contains antihypertensive and anticarcinogenic components and possesses antimicrobial and antiplatelet activities. However, the swollen canned soy sauce sharply tampered with the quality offinal products. Until now, the reason of swollen canned soy sauce is still limited. In this study, the discrepancies of physiochemical and microbial contaminants in the normal and swollen canned soy sauces, which collected from three different regions(southern, northern and central regions) in China, were investigated.⑴ The physiochemical characteristics innormal and swollen canned soy sauces, including p H, total acidity, salinity, deoxidize sugar, lactic acid and acetic acid, were analyzed using basic chemical tests and HPLC. No obviously difference of acetic acid content and the salinity(usually in 16%~18%)were obtained in normal and swollen canned soy sauces. However, the lactic acid concentrations of the swollen canned samples were significantly higher than those in the normal samples, and the reducing sugar concentrations of the swollen canned samples were significantly lower than those in the normal samples. These results indicated that the physiochemical characteristics were changed in the swollen canned soy sauces.⑵ Comparison of microbial contaminants between normal and swollen canned soy sauces were performed using plate techniques and nested PCR-denaturing gradient gel electrophoresis(DGGE). Plate technique showed that four diverse species of Bacillus(B. subtilis, B. oleronius and B. flexus) were present in the swollen canned samples. The PCR-DGGE profiles showed that four lactic acid bacteria(LAB), including Lactobacillus acidipiscis, L. pobuzihii, L. piscium and another Lactobacillus sp., were involved in the swollen canned samples. The dominant contaminated bacteria in normal soy sauce are B.subtilis, B. oleronius, L. piscium, L. pobuzihii, while B. subtilis, B. oleronius, B. flexus, L. piscium, L. pobuzihii, L. acidipiscis, Lactobacillus sp. are the dominant contaminated bacteria inspoilage samples. However, much less bacterial contaminants were detected in the normal samples. These results confirmed the existence of Bacillussp. and LAB in the packaged soy sauce products, and suggested that these contaminants might play a role in the swollen canned soy sauces.⑶L. acidipiscis isolated from soy sauces in this study produced little gas. To further monitor the gas-producing strains, another two gas-producing bacteria(Enterobacteraerogenes, Enterococcus faecium) were isolated from koji samples. Our results showed that E.aerogenes possessed strong gas-producing abilities. Slight changes in the p H were observed after the three bacterial strains were inoculated into soy sauce products. In addition, all of the isolates were temperature-, p H-, and salinity tolerant. The separation and identification of three bacterial strains were important to ensure adequate quality and food safety of soy sauce.In this study, we analyzed the microbial contaminants involved in the swollen canned soy sauce and provided experimental basis and technical information to support the up gradation of quality control during soy sauce fermentation.更多还原