Accumulation Technology Of T-Aminobutyric Acid In Soybean Seed And Development Of Soybean Milk

Soybean (Glycinemax L. Merrill) has high nutritional value and benefits human health with large amounts of protein, amino acid and fat. Soybean food has a long history as one Chinese traditional product. Developing new types of soybean milk products based on germination and nutritional improvement plays a vital role in promoting the traditional soybean product.In this paper, soybean was germinated for a short time under hypoxia. The changes of physical activities and the mobilization of major nutrients of soybean were studied during germination. The changes in GABA accumulation and activity of GAD and DAO were explored during cold stress. The enzymatic reaction condition of homogenate and additives were optimized. Subsequently, soybean rich in GABA were obtained using the optimized process parameters and GABA-enriched soybean milk was developed. The main results were summarized as follows:1. During germinating for 48 h under hypoxia, GABA content, DAO and GAD activities of soybean were all increased. They had highly significant positive correlation (p <0.01) with each other and significant negative correlation (p<0.05) with dry matter content. The optimal germination time for best accumulating GABA in soybean was determined as 24 h.2. The germinated soybean was cultivated at cold stress to further accumulate GABA. The optimal cold stress temperature was-18℃, at which freezing for 12 h and thawing for 6 h could obtain a GABA content of 11.7 times of the control. Besides, it was suggested that GABA synthesis was mainly from the polyamine oxidative degradation pathway.3. Effects of enzymatic reaction time, temperature, pH, VB6 on GABA accumulation were significant (p<0.05), while that of Ca2+ was not significant. The optimal reaction conditions of acidity and neutral soybean milk were obtained by orthogonal experiment, which were at pH 4.0 and 7.0, respectively, reaction time of 80 and 100 min, respectively, VB6 of 300 μmol/L and 500 μmol/L, respectively and temperature was both at 45℃. Under the optimized reaction conditions, the GAB A content reached 4.36 mg/g DW and 5.59 mg/g DW on the acid and neutral environment, respectively.4. The germinated soybean was made into a kind of GABA-enriched soybean milk after the above process. Results showed that the basic ingredients of GABA-enriched soybean milk were as follows:the optimum ratio of sample to solution was 1:7, the soybean milk was emulsioned with 0.06% of monoglycerides and 0.04% of sucrose ester. The stabilizer prescription of GABA-enriched soybean milk was 0.02% of xanthan,0.2% of PGA and 0.01% of compound emulsifier (ratio of polyglyceryl fatty acid ester and monoglycerides was 6:4, HLB 6.7), sucrose addition was 6%. No deposition was observed in the beverage after stored for 45 d at room temperature. The soybean milk was in accordance with consumer drinking requirements.