Antioxidant mechanisms of caseinophosphopeptides and casein hydrolysates and their application in ground beef

Caseinophosphopeptides (CPP) and casein hydrolysates have been shown to bind prooxidant metals such as iron, but their effectiveness as metal chelators to inhibit lipid oxidation in foods has still not been fully investigated. Thus, the antioxidant activity of CPP and casein hydrolysates was studied in phosphatidylcholine liposome model systems. CPP (< 1.0 mg/mL) and casein hydrolysates (0.3-1.7 mg/mL) were effective inhibitors of TBARS development when oxidation was promoted by ferric/ascorbate. High amounts of CPP (> 1.0 mg/mL) were prooxidant, whereas casein hydrolysates were observed to be only antioxidative. In the presence of peroxyl radicals, casein hydrolysates were more effective scavengers than enriched CPP (3-15 mM). In cooked ground beef, TBARS formation was inhibited 75, 39, and 17% by 0.5% enriched CPP, casein hydrolysates, and low molecular weight casein hydrolysates, respectively, after 4 days of storage. The results show that CPP and casein hydrolysates are promising sources of natural antioxidants for foods.