Screeing And Identification Of High-yield Aglycones Soy Isoflavone Of Lactic Acid Bacteria And Its Application In Fermented Soymilk

In this study, for production of functional fermented soymilk, one strain was selected from one hundred lactic acid bacteria isolates based on their capacities to hydrolyze isoflavone glucosides to aglycones by high performance liquid chromatography (HPLC), as the fermentation strain to product functional fermented soymilk. And identified by morphology, physiological characteristic, biochemical tests and16S rDNA sequence analysis, and the fermentation characteristics and storage stability were studied, the main results were as follows:The high-yield soy isoflavone aglycones bacterial strains was No.4, based on the morphological, physiology biochemistry experiments,16S rDNA sequence homology analysis, the strain was classified as Lactobacillus plantarum. The GenBank accession number is KF192886.Fermentation conditions including fermentation temperature, initial pH and inoculation amount were optimized by one-factor-at-a-time and response surface methodology (RSM) to research the factor of soy isoflavone aglycones. The optimum fermentation condition were as follows:the initial pH value was7.12, the fermentation temperature was43.77℃and the inoculation amount was5.25%, where the soy isoflavone aglycones production was118.457μg/mL.Comparison the different processing methods on soybean antinutritional factors (lipoxidase and trypsin inhibitor), such as heat treatment, decorticated, NaHCO3and citric acid salt solution immersion. The results revealed that the optimum pretreatment method to inhibit the soybean antinutritional was hot-milling, the soybean lipoxidase activity decline to26.43%and the trypsin inhibitor activity is52.45%of the untreated.Fermentation characteristics and storage stability of the probiotic Lactobacillus plantarum4were analyzed by determining pH value, proteolytic activity, the viable cells, syneresis of soymilk fermented with Lactobacillus plantarum4. The results revealed that Lactobacillus plantarum4grow well in fermented soymilk, in the process of fermentation, the proteolysis activity and water holding capacity were increased, the viable cells count of soymilk were2.33x108CFU/mL and the titration acidity was68.91°T at the terminal point of fermentation. There were little differences of the acidity, viable cells and syneresis when stored at low temperature, which indicated that the storage stability was superior to that stored at room temperature.For the sensory indicators can be evaluated from apparent, smell, flavor, texture and evaluated, the products showed the best characteristics including the moderate sweet, the suitable acidity, no smell, cooking and beany flavor and the pleasing aroma of beans, no whey separated, the comprehensive score was88.46. Our results indicated that Lactobacillus plantarum4had the potential application to the fermented soymilk and provided the theory basis to the further practical production.