Effects Of Soybean Peptide On The Properties To Fermented Soybean Milk

The promotive effect of soybean peptide on the growth and acid production of lactic acid bacteria was studied in this paper. Soybean peptide was separated and purified by macroporous adsorption resin. Fermented soybean milk added with different peptide fractions was evaluated by microstructure, rheological properties, flavor and sensory evaluation in order to search soybean peptide which was well suitable for industrial production of fermented soybean milk. The aim of this study was to lay a foundation for industrial production of fermented soybean milk.Soybean peptide was eluted with different concentrations of ethanol by hydrophobic adsorption on macroporous resin DA201-C. The yield of peptide eluted by 25% ethanol(v/v) was 48.97%. The content of positively charged peptides was determined by SP-Sephadex C-25 ionic-exchange resin. The results showed that the content of positively charged peptides in peptide fractions eluted by 25% ethanol was obviously low and the yield was 22.50%. There was not significant difference among molecular weight distribution of these peptide fractions.Soybean peptide was added into fermented soybean milk as fermentation promoter for lactic acid fermentation. The effect of soybean peptide on the growth and acid production of lactobacillus was studied. Meanwhile, the vitality of lactic acid bacteria in fermented soybean milk was measured for evaluating the promotive effect of soybean peptide on the maintenance of lactic acid bacteria vitality. The results showed only a amount of soybean peptide could significantly promote the growth of lactic acid bacteria and improve the vitality. When 200mL fermented soybean milk (beans:water(w/w)=1:9) was fermented by Hansen YF-L811,the optimum production conditions of fermented soybean milk with good sensory quality were: fermentation agent 9ml, sucrose 5g, soybean peptide 1g.Fermented soybean milk, and fermented soybean milk added with peptide eluted by 25% ethanol as well as 50% ethanol demonstrate symmetricl network through SEM's observation. There was little effect of soybean peptide on fermented soybean milk consistency. Soybean peptide eluted by 25% ethanol and 50% ethanol reduced pseudoplasticity of fermented soybean milk, but soybean peptide eluted by 75% ethanol and 100% ethanol increased. Soybean peptide could eliminate off flavor of fermented soybean milk, and peptide eluted by 50% ethanol had the best effect. The differences among fermented soybean milk were measured by sensory evaluation. The results showed that the quality of fermented soybean milk added with peptides eluted by 25% ethanol was the best at the 0.05 level of significance. Compared with fermented soybean milk, titration acidity of fermented soybean milk added with peptides eluted by 25% ethanol increased 36.59%, and the corresponded value was 56 oT.