Effects of Pro-Oxidants and Antioxidants on the Total Antioxidant Capacity and Lipid Oxidation Products of Milk During Refrigerated Storage.

Oxidized flavor is a major problem that affects the dairy industry because of its adverse effect on milk acceptability. The objectives of this research were to examine the roles of pro-oxidants and antioxidants on the oxidative stability of whole milk. In the 1st experiment, the effect of light (2300 Lux) and/or cupric sulfate (0, 0.5, and 1.0 mg/kg) as pro-oxidants in milk were investigated during an 11-d refrigerated storage period. The effects of added retinyl palmitate (1.16 mg/L; 2113 IU Vitamin A/L) and tocopheryl acetate (100 mg/kg milk fat; 5.02 IU Vitamin E/L) as antioxidants in the presence of light (2300 Lux) and light with cupric sulfate (0.05 mg/kg) during a 7-d study were investigated in the 2nd experiment. The presence of pro-oxidants significantly (P < 0.05) decreased the total antioxidant capacity (TAC) and increased the lipid oxidation products in milk during storage. Light had a greater effect in the decrease of TAC, although cupric sulfate in the presence of light significantly increased the formation of lipid oxidation products. The addition of antioxidants resulted in a significant (P < 0.05) increase in TAC on day 0. However, with exposure to light and light with cupric sulfate, the antioxidants did not result in a higher TAC in comparison to the treatments without added antioxidant. Analysis of lipid oxidation products by instrumental and sensory methods showed that the presence of light and cupric sulfate significantly (P < 0.05) increased the oxidized flavor from the control, but no significant (P > 0.05) difference in oxidized flavor intensity was detected between milk with and without added antioxidants.

PRACTICAL APPLICATION: Production and processing variables can affect the content of pro-oxidants and antioxidants in milk, which has an impact on flavor. An understanding of the role of these components in contributing to or minimizing off-flavor formation in milk, will help dairy producers to provide quality products to consumers.