Acid production by lactic acid bacteria in soy milk treated by microbial protease or papain and preparation of soy yogurt
1989
Ko, Y.T. (Duksung Women's Univ., Seoul (Korea R.). Dept. of Foods and Nutrition)
The soy milk prepared from soy protein concentrate was treated with microbial protease or papain. Growth and acid production by Lactobacillus acidophilus in soy milk containing partially hydrolyzed proteins were investigated. Sensory evaluation of yogurt beverage prepared from protease treated soy milk was also performed. Protease treatment of soy milk enhanced acid production by lactic acid bacteria, particularly in case of microbial protease and simultaneous treatment by two types of protease showed synergistic effect. pH and number of viable cells were not affected markedly by protease treatment. Microbial protease treatment up to 15 minutes or papain treatment up to 45 minutes enhanced acid production, but further treatment up to three hours did not affect the acidity markedly. The sensory evaluation showed that overall acceptability and taste of soy yogurt beverage were slightly improved when soy milk was treated with microbial protease of 0.2 % or papain of 0.2 %. The amount of non-protein nitrogen considerably increased by protease treatment of 15 minutes and it increased gradually by further treatment up to three hours
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