Light-induced protein and lipid oxidation in low-fat cheeses: Effect on degree of enzymatic hydrolysis

The effect of proteolysis on oxidation in low-fat cheese was investigated. The accumulation of dityrosine during storage increased significantly in the cheese with a high degree of proteolysis, while hexanal and heptanal were lower in the cheese with high proteolytic activity, indicating that the peptides/free amino acids acted as antioxidants on the propagating step in lipid oxidation. Dimethyl disulphide concentration was also lower in the cheese with a higher level of peptides. Therefore, oxidation of tyrosine residues seemed to function as antioxidants both regarding secondary lipid oxidation products and protein-derived oxidation products through formation of dityrosine, being a termination reaction.