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Changes of the Proteins in Cheddar Cheese Made from Milk Heated at Different Temperatures

Department of Food Science, University of Illinois, Urbana

ABSTRACT

This investigation determined the changes which occurred in the proteins of cheese made from four lots of milk heated, respectively, at 61.7 C for 30 min and at 93.3, 110.0, and 126.7 C for 2.08 sec, and the effect of these changes on the quality of the cheese. Results showed that protein degradation, as measured by the noncasein and noncasein protein nitrogen production, became greater as heat treatment of the milk increased. No qualitative differences were observed in the amino acid patterns of the four lots of cheese, but the rate of amino acid liberation decreased as the heat treatment of milk increased. Polyacrylamide-gel electrophoresis of the proteins in cheese revealed _s-casein to be extensively degraded and formed seven components, whereas ß-casein formed six after 190 days of ripening. Heat treatment of milk did not produce any qualitative differences in the electrophoretic patterns of the proteins of cheese.

The moisture content was higher in cheese made from milk heated at the higher temperatures, but there were no differences in the fat content. Organoleptic evaluation of the cheese revealed that Cheddar flavor did not develop and the body was weak and crumbly in the cheese made from milk heated at the higher temperatures. A sulfide, cooked flavor was apparent in the lot made from milk which had the highest heat treatment.