| In this study, a number of lactic acid bacteria strains with excellent fermentation characteristics were isolated from kefir grains and naturally fermented sauerkraut. Based on the obtained strains, we developed a fermented milk beverage to broaden the fruit and vegetable processing.By morphology, gram stain and catalase test,10 lactic acid bacteria strains were chosen for further research. And among these strains, strain 299 showed outstanding capacities on resistance to high concentration of acid, bile and salt, and low resistance to antibiotic. The results showed that strain 299 would have extensive application in food and health products.By API experiments and molecular biology methods, strain 299 was identified as Lactobacillus plantarum and named Lactobacillus plantarum 299.The optimal culture temperatures of Lactobacillus plantarum 299 is 30 ℃, pH value is 6.0, the best harvest time is 21st h.By single factor experiment and central composite experiment, we optimized durian beverage fermented process. The optimum formula of fermentation technology was:flesh: water=1:4, sugar concentration 7.6%, milk concentration 10%, Lactobacillus plantarum 299:Lactobacillus bulgaricus:Streptococcus thermophilus=4:1:1, inoculation 2.5×108 cfu/mL, fermentation time 5.5 h, temperature 37 ℃, sterilization condition 85 ℃,10 min. The physiological indicators and health indicators are consistent with GB/T 16321-2003.By HPLC method, the changes of organic acids during the durian beverage fermentation process were analyzed. The results indicated that the lactic acid was as high as 170.72 mg/100g and the content of citric acid and acetic acid were increased. GC/MS was used to analyze the volatile flavor compounds of fermented durian beverage. The mercaptan oxidation of fermented durian beverage was increased so that the aroma of products was improved.The physical changes of fermented durian beverage were measured during preservation. The durian beverage shelf ilfe was 21 d,4 ℃ refrigerated. |
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