Abstract: In this study,vegetable soybean was fermented to produce yoghurt by the combined starter of Lactobacillus bulgaricus and Streptococcus thermophilus with the ratio of 1:1.Through orthogonal test,the optimal formula of stabilizer for the yoghirt is sodium carboxymethylcelluose 0.10%,sodium caseinate 1.0% and sodium alginate 0.25%. By means of qudractic orthogonal rotation comdination design of four factors,the optimal fermentation conditions of vegetable soybean are determined as follows:amount of inoculation:1.4%,temperature 42 ℃ and time 4 h. The optimal formula of vegetable soybean yoghurt is:vegetable soybean soymilk-reduced milk ratio 7:3,sugar 8% and the composite stabilizer 1.3%.

Key words: vegetable soybean, lactic acid bacteria, soymilk, ferment