Physicochemical Properties and ACE-I Inhibitory Activity of Protein Hydrolysates from a Non-Genetically Modified Soy Cultivar

Arkansas-grown non-genetically modified soybean cultivar, R08-4004, was selected to prepare a protein isolate, which was treated with Alcalase for limited enzymatic hydrolysis. The objective was to optimize the Alcalase hydrolysis condition to produce soy protein hydrolysate (SPH) with high protein yield, low bitterness, and clarity for beverage applications. The degree of hydrolysis ranged between 14 and 52 % during the study at varying incubation times using two different concentrations of Alcalase enzyme. Recovery of soluble protein, between 21 and 53 %, was achieved with a decrease in turbidity. There was an increase in surface hydrophobicity (S (0)) which is correlated with bitterness of SPH treated with 1.0 AU (3.2 A mu L/g) of Alcalase 2.4 L. The sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis showed a distinct hydrolysis pattern in which 7S globulin and the two acidic sub-units of 11S globulin were hydrolyzed extensively in comparison to the two basic sub-units of 11S globulin. Limited enzymatic hydrolysis produced low molecular weight peptides < 17 kDa. Among these SPHs, the one derived after 120 min incubation had the highest soluble protein yield (43 %), low S (0) value (35.4), low turbidity (0.88), and highest angiotensin-I converting enzyme (ACE-I) inhibition activity (66.6 %). This hydrolysate has potential use as protein rich nutraceutical for developing many non-genetically modified food product applications.