Effects of lipid oxidation initiators and antioxidants on the total antioxidant capacity of milk and oxidation products during storage
Oxidized flavor is a major problem currently affecting the dairy industry. The objectives of this research were to determine the effects of light (2300 Lux) and/or cupric sulfate (0, 0.5, 1 mg/kg) as pro-oxidative factors in milk during an 11-day refrigerated storage period. The effects of added vitamin A (2113 IU/L) and vitamin E (100 mg/kg milk fat) as potential inhibitors of oxidation in the presence of light (2300 Lux) and light with cupric sulfate (0.05 mg/kg) during a 7-day refrigerated storage were also investigated. The presence of pro-oxidants significantly decreased the total antioxidant capacity (TAC) and increased the oxidation products in milk during storage. Light had a greater effect in the decrease of TAC, while cupric sulfate in the presence of light significantly increased oxidation products. Added vitamin A and E showed a significant (p<0.05) increase in TAC when samples were exposed to light on day 0. On day 1, only vitamin A significantly increased TAC when samples were exposed to light and cupric sulfate. Oxidation products were not affected by the presence of either vitamin A or E. Sensory results showed that the presence of light and cupric sulfate significantly increase oxidized flavor score from the control, but no significant difference in oxidized flavor intensity was detected between milk with added vitamins and milk without added vitamins.