Proteolytic and milk-clotting activities of calf rennet processed by high pressure homogenization and the influence on the rheological behavior of the milk coagulation process

Abstract

This work studied the effects of high pressure homogenization (HPH) on the performance of a commercial calf rennet. The enzyme solution was processed at 50, 100, 150 and 190 MPa and then stored for up to five days at 4 °C. The effects were evaluated on the proteolytic and milk-clotting activities of the enzyme and on the rheological behavior of the milk gels obtained using the processed enzyme. HPH caused a reduction in proteolytic activity with increase in pressure (up to 52% loss of activity at 190 MPa). At the first 48 h of storage, the processed enzyme maintained its activity while the non-processed sample showed a continuous reduction in activity. The results showed that HPH processing did not alter the milk-clotting activity and the rheological tests showed high G' values for the milk coagulated with the enzyme processed at 190 MPa (7% higher after 84 min of coagulation). Thus, HPH improves the milk coagulation by calf rennet and reduces the proteolytic activity of enzyme, which may improve the quality of fresh cheeses, especially after their storage. The changes caused by HPH in the calf rennet improved the cheese manufacturing process and the quality of the product (higher consistency of the milk gel and lower proteolysis during storage). Therefore, the HPH processing of calf rennet can improve its application in the dairy industry to obtain high quality fresh cheese and an extended shelf-life.