Study on the Aggregation of Transglutaminase on Soybean Protein Hydrolysates

Taking soybean protein hydrolysates (SPH) hydrolyzed by papain as substrates, the effects of transglutaminase on soybean protein hydrolysates were studied using the single factors of temperature, time, the ratio of emzyme to protein and pH value. The molecular weight data indicated that transglutaminase could be used as catalyst to aggregate SPH. The solution of the concentration of the enzyme for 25U/g SPH, after heating 40°C for 9h , under pH 7 and formed aggregates with different aggregation profiles. It was also found, by Nitrogen Solubility Index(NSI) measurement, the level of NSI was in the order of native soybean protein<; soybean protein hydrolyzed by papain<; soybean protein aggregated by transglutaminase. Both these results showed that when SPH aggregated by transglutaminase, the molecular weight of SPH increased obviously, the solubility of SPH was improved to a certain extent.The aggregation character might be widely used as a source of highly functional soybean protein in more food products.