Study of methods to routinely monitor heat load to cheese milk

The quality of cheese made from pasteurised milk depends on limitation of the heat load to cheese milk. Analysis of heat denatured whey proteins and inactivated milk enzymes were evaluated for routine testing of heat load using pasteurisation and microfiltration equipment currently used in the production of semi-hard cheese. Significant differences between the routinely used milk treatments were seen when heat denatured alpha-lactalbumin and beta-lactoglobulin were analysed by capillary electrophoresis, or the inactivation of two milk enzymes were analysed with simple colorimetric methods. GGT, gamma-glutamyl transpeptidase (EC 2.3.2.2) retained 35-70% of its activity and NAG, N-acetyl-beta-glucosaminidase (EC 3.2.1.30) 1-12% after the milk treatments. The results show that, similar to the alkaline phosphatase test for pasteurised milk, tests can be developed that give an NAG positive result to assure that the properties of importance to cheese ripening have not been lost. (C) 1999 Elsevier Science Ltd. All rights reserved.