Effect of high pressure treatment at various temperatures on the rennet clotting behavior of bovine and ovine milk

The objective of the present work was to compare the effect of high pressure (HP) treatment at 200, 450 and 650 MPa at various temperatures (20, 40 and 55 degrees C) on rennet clotting behavior of bovine and ovine milk. The HP treatment of bovine milk at 200 MPa at all temperatures decreased the rennet clotting time (RCT) and increased the curd firmness. Treatment at 450 MPa and temperature >20 degrees C impaired both parameters and at 650 MPa no clotting occurred. The coagulation failure was restored after supplementation of the pressurized milk with CaCl(2), although the type of the resulting curd is expected to be different. In contrast to bovine milk the applied HP treatments did not affect significantly the RCT of ovine milk. The same was true for curd consistency at treatments of 200 MPa at 20 or 40 degrees C. However, treatment with 200 MPa at 55 degrees C or 450 or 650 MPa at all temperatures decreased it significantly. These findings demonstrate that the HP effect on the structural elements of ovine milk is different compared to bovine milk.