Partial identification of water-soluble peptides released at early stages of proteolysis in sterilized ovine cheese-like systems: influence of type of coagulant and starter.

Cheese-like systems were manufactured from sterilized ovine milk, using crude aqueous extracts of Cynara cardunculus or cardosin A isolated therefrom as clotting agent. The effect of adding a commercial starter culture was also assessed. The impact of the type of coagulant used during the initial 24 h of proteolysis was evaluated via separation of peptides in the water-soluble extracts by reverse-phase HPLC, followed by partial sequencing via Edman degradation. Cardosin A accounted for most events of primary proteolysis. The major cleavage sites were Phe105-Met106 in kappa-casein, and Leu127-Thr128, Ser142-Trp143, Leu165-Ser166, and Leu190-Tyr191 in beta-casein. The starter culture did not play an active role during the initial stages of ripening.