Caseinolytic activity of fruit extract from Opuntia ficus-indica on bovine, caprine, and ovine sodium caseinates

The rates and extents of hydrolysis of alphas- and beta -caseins from bovin e, caprine, and ovine sodium caseinates produced by an enzymatic extract of the fruit of Opuntia ficusindica, (L.) Miller were evaluated and compared with those produced by a commercial animal rennet. A mechanistic model base d on a pseudo-first-order enzymatic reaction, in the presence of first-orde r deactivation of the enzyme, was postulated and successfully fitted to the experimental data. The animal rennet exhibited higher enzymatic efficiency than the fruit extract, irrespective of the source (i.e., bovine, caprine, or ovine) and the type (i.e., alphas- or beta -casein) of substrate. The e nzymatic efficiency (k(cat)/K-m) for alphas-casein ranged from 72 to 220 an d from 43 to 65 L g(-1) h(-1), and for beta -casein from 242 to 742 and fro m 55 to 164 L g(-1) h(-1), for the animal rennet and the enzymatic extract of O. ficus-indica, respectively. Finally, it was observed that beta -casei n from caprine and ovine caseinates was degraded by O. ficus-indica faster than its alpha (S) counterpart, but the reverse was observed for bovine cas einate.