Physicochemical properties and biological activities of ovine caseinate hydrolysates

Caseins are the precursors of bioactive peptides, which can be released through enzymatic hydrolysis and subsequently be incorporated into food products. This investigation evaluated the antioxidant and antimicrobial activities, as well as the physicochemical features, of ovine sodium caseinate (NaCAS) subjected to proteolysis. A Bacillus sp. P45 protease preparation was utilized in the hydrolysis of ovine NaCAS, for up to 7 h. Absorbance and intrinsic fluorescence spectra suggested that the hydrolysis of NaCAS exposed aromatic amino acids to the aqueous media. Following a slight decrease in the surface hydrophobicity (S (0)) observed up to 2 h of hydrolysis, S (0) increased in the hydrolysates from 3 to 7 h, indicating exposure of hydrophobic groups on the surface of the generated peptides. An increase in the antioxidant properties, evaluated by the 2,2'-azino-bis-(3-ethylbenzothiazoline)-6-sulfonic acid method, was observed following hydrolysis up to 4 h. One-hour hydrolysates inhibited the growth of Salmonella enteritidis, Escherichia coli, Corynebacterium fimi, and Listeria monocytogenes, showing antifungal activity of the hydrolysates. The gelation ability of the hydrolysates was maintained, as evaluated through acid aggregation induced by glucono-delta-lactone (GDL). Although aggregation occurred at slower rates than that of nonhydrolyzed samples, the compactness of the aggregates formed from 1- to 2-h hydrolysates was comparable to that of nonhydrolyzed NaCAS. The final state of aggregates formed from NaCAS/hydrolysate mixtures (4:1) was not altered. Thus, these functional hydrolysates might be potentially added to dairy products manufactured through acid-induced aggregation, without significantly affecting this process.