β-Casein Degradation in Gouda and Cheddar Cheese

Abstract

High concentrations of high molecular weight peptides of low electrophoretic mobility occurred both in 11 mo old Gouda and 30 mo old Cheddar cheese. Three peptides isolated from each variety of cheese have been identified as γ-casein A2, TS-casein A2, and R-casein, by electrophoretic mobility, amino acid analysis, molecular weight determination, and mobility changes on gel electrophoresis in the presence of magnesium ions. The enzyme known as milk protease cleaves the β-casein A in milk between residues 28 and 29, 105 and 106, and 107 and 108 to give γ-, TS-, and R-caseins, respectively. It is probable, therefore, that β-casein is slowly degraded by milk protease in ripened cheese at a rate which is probably determined by the moisture content and pH of the cheese. © 1975, American Dairy Science Association. All rights reserved.