Identification of Peptides from Ovine Milk Cheese Manufactured with Animal Rennet or Extracts of Cynara cardunculus as Coagulant

Urea-PAGE of the water-insoluble extract (WISE) of ovine raw milk cheeses manufactured with proteinases of Cynara cardunculus or with commercial animal rennet indicated that the animal rennet acts more intensively, in quantitative terms, on ovine β-, α_s1-, and α_S2-caseins than the plant rennet. The water-soluble extract (WSE) from cheese produced by plant rennet was constituted by fragments of ovine β- and α_S2-caseins; peptides β-(f128-*), β-(f166-*), and β-(f191-*) were produced only by plant rennet, whereas peptides β-(f164-*) and β-(f191-*) were produced only by animal rennet. The peptide β-(f1-190) was identified as the primary product of ovine β-casein degradation in the WISE for both rennets. The complementary peptides α_s1-(f1-23) and α_s1-(f24-191) were produced by both rennets from ovine α_s1-casein; however, the bond Phe23-Val24 was cleaved by as early as 7 days in cheese manufactured with C. cardunculus, whereas 28 days had to elapse before that could be detected in the case of animal rennet. The peptide α_s1(f24-165) was produced only by plant rennet, whereas the peptide α_s1-(f120-191) was produced only by animal rennet. The peptides produced from bovine α_S2-casein in cheese could not be traced as deriving from the action of proteinases from either rennet, so their existence is likely due to proteinases or peptidases released in cheese as a result of its indigenous microflora.