Isolation And Identification Of Spoilage Microorgnisms In Pickled Vegetable And Their Influence On Quality Of Pickles

The quality of pickles has a strong relationship with lactic acid bacteria, however, the quality deterioration of pickles caused by spoilage microorganisms has a huge effect on taste, appearance and flavor of pickles. Therefore, it is very important to control the spoilage organisms during production to ensure the safety of pickles. In this study, six deterioration pickle samples were collected from the Ya’an market and a pickle factory. These samples were cultured in PDA and NA media, which aims to isolate the spoilage organisms. According to the colony characteristic and sequence analysis,7 strains were identified as suspected spoilage organisms. Thereafter, these strains were subjected to some physiological and biochemical tests. Furthermore, the effect of these strain on the quality of pickles were studied. The main conclusions are showed below.1. Thirty-one strains isolated from samples were used to sequence the 16S rDNA/18S rDNA gene. Except 3 of lactic acid bacteria, the other 28 strains were used to sequence alignment, and structure the phylogenetic tree. The results showed that 4 funguses were Candida xestobii, Kodamaea ohmeri, Candida tropicalis, Geotrichum candidum respectively; Bacillus subtilis(8), Bacillus merhylotrophicus(2), Bacillus amyloliquefaciens(2), Bacillus aerius(3), Staphylococcus xylosus(1), Bacillus thuringiensis(4), Brevibacillus agri(1), Bacillus aryabhattai(1), Bacillus niacin(1) and Paenibacillus cineris(1).2. According to the physiological and biochemical tests, the G.candidum, S.xylosus and C.tropicalis have stronger acid resistance. G.candidum can promote acidification, accelerate the decrease of pH. Seven spoilage organisms can metabolize nitrate to nitrite. G.candidum can metabolize 4 kinds of carbohydrate, and S.xylosus can be only used to metabolize sucrose.3. Seven suspected spoilage organisms were inoculated in pickles. And the deterioration happened during the fermentation under different temperature. G.candidu was inoculated pickles at 15℃ generated the white membrane and has the lowest pH. K.ohmeri, S.xylosus, B.thuringiensis and B.amyloliquefaciens were inoculated pickles happened brown stain at 37℃, and much bubble were produced with thrill smelling, nitrite containment is very high, which is above 0.9g/100g. During the fermentation, the concentration of total acid’s and amino nitrogen increased, however, the content of sugar decreased, which is similar to others studies. Furthermore, the volatile substances are tested in this study and 45 kinds of volatile substance are identified. Among these substances, sulfide has the highest contend.17 kinds of volatile substance were test in traditional fermentation pickles which inoculated the spoilage organisms, and isothiocyanate was the main part of them, which is up to 55%.4. The final result shows that Cxestobii、G.candidum、S.xylosus、B.thuringiensis、 B.amyloliquefaciens could lead to the spoilage of pickles, which were identify as the spoilage organism of pickles.