Limited hydrolysis of soybean protein concentrate and isolate with two proteases and the impact on emulsifying activity index of hydrolysates

Soy protein concentrate (SPC) and soy protein isolate (SPI) were limited hydrolyzed with trypsin or neutrase under controlled hydrolysis conditions. Eight soybean protein hydrolysates, 4 SPC  hydrolysates and 4 SPI hydrolysates were prepared with degree of hydrolysis (DH) of 1 or 2%. SDS-PAGE was used to determine the hydrolysis profiles of soybean proteins in these hydrolysates. Emulsifying activity index of these hydrolysates were also evaluated. Analysis results from SDS-PAGE indicated that these hydrolysates had different peptide compositions due to the differences of enzyme specificity and degree of hydrolysis. SPC hydrolysates or SPI hydrolysates prepared with trypsin had more large peptides than that prepared with neutrase. The hydrolysates prepared with trypsin exhibited better emulsifying activity index than that with neutrase, especially when degree of hydrolysis of hydrolysates was 1%. Both protease used and DH obtained had influence on the emulsifying activity index of soybean protein hydrolysates prepared.