INFLUENCE OF PASTEURIZATION OF MILK ON PROTEIN BREAKDOWN IN CHEDDAR CHEESE DURING AGING

Cheddar cheese was made from pasteurized (63-degrees-C for 30 min) and raw milk. The extent and characteristics of proteolysis were monitored during 6 mo of aging. Pasteurization decreased the rate of production of 12% TCA-soluble nitrogen during cheese aging. The breakdown of beta-casein and the high molecular weight proteolytic products of alpha-s-caseins that comigrated with beta-casein (as measured by SDS-PAGE) was slower in cheese made from pasteurized milk. The total amount of water-soluble peptides measured by HPLC at wavelengths of 214 nm and 280 nm was similar in cheeses made from pasteurized and raw milk. However, there was a higher ratio of water-soluble hydrophobic to hydrophilic peptides in Cheddar cheese made from pasteurized milk. Thus, milk pasteurization prior to Cheddar cheese manufacture influenced both the extent and characteristics of proteolysis during Cheddar cheese aging. Milk pasteurization caused heat-induced interaction of whey proteins with casein and resulted in retention of additional whey protein in the cheese beyond that normal amount which is soluble in the aqueous phase of the cheese. The presence of heat denatured whey protein in cheese may influence the accessibility of caseins to proteases during cheese aging and cause differences in proteolysis during aging. These differences may be one factor that contributes to differences in flavor development in Cheddar cheese made from pasteurized and raw milk.