Abstract:

Soybean protein hydrolysates (SPHs) with a degree of hydrolysis of 16.6% were prepared by 4 h hydrolysis with alcalase, and then subjected to plastein reaction for modification. Response surface analysis was applied to optimize the conditions for plastein reaction, and the optimal conditions obtained were as following: substrate concentration 45%, enzyme loading 275 U/g proteins, reaction time 3 to 4 h and reaction temperature 30 ℃. Nine modified products were prepared, and their ACE inhibitory activities were evaluated in vitro. It was found that the IC50 values of the modified products were in the range of 0.64 to 1.30 mg/mL, lower than that of SPHs (1.45 mg/mL). The analytical results from size exclusion chromatography confirmed that more large peptides with higher molecular weight were generated in the modified products. This study suggests that enzymatic hydrolysis coupled with plastein reaction might be served as a new approach to prepare ACE inhibitory peptides with higher activity from soybean protein isolate.

Key words: soybean protein hydrolysates, plastein reaction, ACE inhibitory activity, alcalase, size exclusion chromatography