Studies On The Process Technology And Gelation Characteristics Of Soymilk Fermented By Lactobacillus Acidophilus

This paper investigated the treatment of off-beany flavor,culture domestication,the fermentation process of soymilk,the analysis of flavor components in fermented soymilk,formation of soy-gel and factors which affect the gels formation.According to the physical and chemical analysis and sensory evaluations,four off-beany treatments including the heat treatment and alkali-treatment were compared,the soymilk without beany flavor can be obtained at the condition of blanching at 90℃for 10～15min and milling at 90～100℃.The way of increasing the concentration of soymilk in the substrates was used for the culture domestication.The gelation time and acidity of fermented soymilk are 4.57h and 76.67°T which are 27% less and 32%higher than those of undomestication respectively.After 25 times domestication,the acidity and numbers of active culture are 100.70±1.16°T and 2.53×10~8cfu/mL,respectively.The optimum technology parameters were investigated by Box-Behnken design and ridge analysis,the result showed that the optimum fermented conditions were as follow:soybean:water=1:6, pasteurization at 116℃for 15min,fermented at 40℃for 8h with the inoculum dosage 5.0%and skim milk powder addition 1.9%.About 30 flavor components were identified and compared in fermented soymilk,fermented milk and fermented mixture of soymilk and milk.The contents of 2,3-diacetyl increased when some milk were added into the soymilk before fermentation,meanwhile,the contents of three unsatisfied flavor components(hexanol,2-pentyl-furan and hexanal)were reduced.The flavor of fermented soymilk was distinctly improved when some milk added before the fermentation.Different ratio of soymilk and milk,gelation temperatures and heat treatment were studied by the dynamic viscoelasticity test and SEM scanning.When the soymilk is fermented by Lactobacillus acidophilus,the soy-gel with higher hardness of gel,denser network structures and fewer whey separation was obtained at 40℃with pure soymilk which is heated higher than 90℃before fermentation.