Study On Safety Of Pickles And Isolation, Screening And Identification Of Preferable Lactic Acid Bacteria

In this paper, safety of pickles, which is a Chinese traditional lactic-fermented food, was mainly studied.Twenty commercial pickle samples were collected from different Chinese regions and investigated for chemical and microbiological analyses from food safety point of view. The results showed that content of nitrites and volatile nitrosamines were significantly different according to the varieties of pickles. Compared with the varieties of radish and cucumber pickles, content of nitrites and volatile nitrosamines in the variety of cabbage pickles were significantly high, while those in radish pickles were significantly higher than cucumber pickles'. Microbiological analyses showed that high level of LAB (lactic acid bacteria) occurred in most samples and low level of fungi were found in a part of samples, while all samples contained some surviving but inactive bacterial endorspores and no Enterobacteriaceae. From microbiological point of view, all products were safe.Concentration of edible salt had great effects on the microbiological community and content of noxious compounds during pickles fermentation. High Concentration of brine (10%) made the heterofermentation of LAB prolonged as well as fungi and Enterobacteriaceae inhibited significantly, while low concentration of brine (4%) made the heterofermentation of LAB condensed and Enterobacteriaceae and bacterial endospores inhibited effectively. In the same time, addition of garlic, ginger and clove influenced microbiological composition and decreased content of nitrites to some extent in the initial fermented stage, which was very advantageous to enhance safety of pickle products.Two preferable strains of LAB were obtained from fresh pickle brines through the screening criterions which included velocity of acid production, ability of nitrites decomposition, ability of biogenic amines production and ability of antibacterial matters production. Identification of the two LAB strains by API CH products showed that they were Lactobacillus plantarum and Carnibacterium divergens respectively.