| In this study soybean was used to produce a good quality of fermented soybean yoghourt.This can increase the digestibility and nutrition value of soybean protein. This paper investigated the process of soybean milk making, the hydrolization process of soybean milk, the fermentation process of soybean hydrolysis production.The process of soybean milk making was studied,and effects of soak time,soak temperture,soak pH value,rate of soybean and water, heat treatment time,heat treatment temperature, pulping time,addition of NaHCO3 on dissolution rate of soybean protein were analyzed.The optimum technological conditions were:soak time16.2h, soak temperture 29.2℃, soak pH7.0, rate of soybean and wate 1∶8, addition of NaHCO33％, heat treatment time 8.2min,heat treatment temperatur80℃, pulping time 8min,in this condition dissolution rate of soybean protein is 83.5％.Based on the study of the process of soybena protein hydrolization by papin, the optimum conditions were: time of hydrolyze 6.12h, pH value of hydrolyze 5.2, temperature of hydrolyze 64.9℃, addition of papain0.986％.In thiscondition,DH is about 9.36％. The process of soybena protein hydrolization by Bacillus natto was also studied and effects of growth curve, initial pH value, temperature of fermentation, rocking revolutins, inoculation volume,time of fermentation were analyzed.The results showed that the optimum conditions were: temperature of fermentation 39.7℃, inoculation volume 7.12％, time of fermentation 54.3h,initial pH 7.0 value, inoculation time 10h, rocking revolutins 120rpm,in this condition DH is about 13.58％. The DH of soybean protein by using papin and Bacillus natto was 15.66％which was 6.3％higher than that using papin and 2.08％higher than that using Bacillus natto.Molecular weight distributions of soy milk and hydrolysates were determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis.The SDS-PAG profile of soybean polypeptides showed that, hydrolysates molecular weight is lower than 6.5KD. Nattokinase molecular weight is lower than 20KD higher than 14KD. The function of soy bean hydrolysates was studied primarily. The result showed that bean hydrolysates had mang physiolgical functions such as promoting bacterium acidi lactici growth and the antioxidative activity.The relative antioxidative activity of hydrosates in three papin and Bacillus natto hydrosates was -15.12％was the maximum, others in turn were Bacillus natto hydrosates, papin hydrosates were -10.43％,-8.50％,respectively.The effect of prdiferation of strain was investigated by applying the hydrdysate to the fermented milk.The result showed that the hydrdysate stimulated the growth of the bacteria and the OD value is 2.5 times than the control group.The process of lactic acid fermentation was studied,and effects of fermentation time, inoculation volume, addition of lactose, fermentation temperature were analyzed. The results showed that the optimum conditions were: fermentation time 10h, inoculation volume 4.35％, inoculation volume 2.51％, fermentation temperature 42.37℃,in this condition the acidity of soybean yoghurt was 98.50T. The soybean yoghurt aftermature at 4℃for 24h, the acidity of soybean yoghurt was 7.50T higher and become more delectable flavour.CMC and Xanthan Gum were the chosen stabilizers.Based on the experiment, the optimum added amount of stabilizers, sucrose, lactic acid,and sterilization parameters were obtained.The results indicated that the best formula of this kind of fermented soybean drink with the greatest stability were: CMC: Xanthan Gum=2:1, 0.2％of stabilizers, 10％of sucrose, 0.2％of lactic acid, and pasteurizing under 80℃for 20min.The sensory and microorganism target of fermented soybean drink were studied for 10 days and conformed to the Chinese Standards.
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