Abstract:Soybean meal, as a byproduct of soybean oil manufacture, contains mainly of protein. Peptides derived from the protein had been proven to be angiotensin-converting enzyme (ACE) inhibitory and antihypertensive effect. Food-grade soybean meal was hydrolyzed by alcalase for the preparation of ACE inhibitory peptides. The optimum enzymolytic conditions for the preparation were at pH8.0, 55 ℃ for 3 h and a substrate concentration of40 g/L. The ACE inhibitory activity and the degree of hydrolysis (DH) were separately high up to 64.21％ and 14.86 %. Subsequent detection of high performance liquid chromatographic (HPLC) and High pressure liquid chromatography / quadrupole - time of flight tandem mass spectrometry (LC-MS) suggested that the active fraction might be tripeptide with molecular weight of 359 and the molecular formula of C15H30N6O4 which constitute of Isoleucine, Arginine and Alanine. Its HPLC conditions were determined as follows: column, ZORBAX SB-C18(4.6 mm id×150 mm, 5 um); detection wavelength, 228nm; mobile phase, methanol - ultra-pure water (50:50, v/ v, both containing 0.1%(v/ v) trifluoroacetic acid; flowrate, 0.7 mL/min;column; temperature, 26 ℃; sample size,10μl.