Process Optimization And Allergenicity Assessment Of Fermented Soymilk By Lactobacillus

Soymilk has high nutritive value which contains rich protein,as well as lecithin,isoflavones and other functional components,and it is a good substitute for those people who was allergic to milk and lack of lactase in the body because of its lower contents of lactose and cholesterol.Soymilk is also an important source of plant protein.However,soybean,as the raw materials of soymilk,is one of eight major allergenic foods recognized by WHO/FAO.The anti nutritional factors and allergenic proteins in soybean greatly reduced the application range of soymilk.Recently,research has been mainly focused on the reduction in the allergenicity of allergenic food by microbial fermentation.However,some studies about the soymilk are just fouse on strains and its bio-active functions,and little information is available for the effects of fermentation on the allergenicity of soymilk.The aim of the study is to explore process optimization and allergenicity assessment of fermented soymilk by lactobacillus,which would provide the theoretical basis for development of high-quality,hypoallergenic fermented soymilk products.Several works are involved in this study including the following three aspects: Firstly,selection of the strains and optimization of the liquid fermentation conditions for soymilk.Secondly,analysis of physicochemical properties,texture properties and rheological properties of fermented soymilk.Thirdly,allergenicity assessment of fermented soymilk.The main methods,results and conclusions are addressed as follows.1.The liquid state fermentation of soymilk was fermented by mixture of Lactobacillus brevis and lactobacillus.sp after the selection of strains,and the conditions were optimized by single factor experiment and orthogonal experiment based on analysis of percentage of total protein content below 20 k Da in fermented soymilk using SDS-PAGE.The results showed that the optimum fermentation conditions were the inoculation amount of 4%,the ratio of Lactobacillus brevis and Lactobacillus.sp of 3:2,fermentation temperature of 33℃,fermentation time of 24 h.2.The binding capacity of fermented soymilk to specific antibody was evaluated by indirect competitive ELISA.The results showed that fermentation could significantly reduce the binding capacity of soybean protein to specific IgG and IgE.After the sensitization of the fermented soymilk in BALB/c mouse model,the IgE content in the serum of mice was decreased,while the content of IgG increased.Meanwhile,IL-4,IL-5,IL-13 and other cytokines were significantly decreased compared with the soymilk group,and the content of IFN-γ increased significantly.In addition,the levels of degranulation of mast cells and basophils were also decreased.Based on the above experiments,it concluded that the fermented soymilk can regulate the Th1/Th2 balance of mice to the Th1,thus alleviating the allergic symptoms in mice.The clinical symptoms and intestinal tissue sections of mice also showed that the fermentation process could reduce the potential allergenicity of soymilk.3.Partial physicochemical properties of the fermented soymilk under optimal conditions were analyzed according to the requirements of National standard.The results showed that the main physicochemical indices meet the requirements of National standard.The molecular weight distribution of fermented soymilk was analyzed by size exclusion chromatography-high performance liquid chromatography(SEC-HPLC).The soy proteins were degraded into small molecular peptides after fermentation,and the proportion of peptides with molecular weight below 2 kDa amount to 49.7%.4.The texture and rheological characteristics of fermented soymilk were analyzed by texture analyzer and rheometer.Compared with yogurt produced under the same condition,soymilk have better performance on hardness,cohesiveness and chewiness,and the soymilk showed better viscoelasticity and shear thinning property than that of yogurt.Finally,the gel dehydration sensitivity of soymilk was lower than that of yogurt.