Antioxidant Properties of Milk: Effect of Milk Species, Milk Fractions and Heat Treatments

Background and Objective: Oxidative stress is a term denoting an imbalance between the production of oxidants and the respective defense systems of an organism. Oxidants include reactive oxygen species (ROS), reactive nitrogen species (RNS) and others. Oxidative stress is deemed a causative factor of neurodegenerative disorders, cancer, liver injury, aging, diabetes, chronic pancreatitis and cardiovascular disease. In this study, the antioxidant activity of different milk species was investigated. Also, which milk components are responsible for antioxidant activity were also determined. In addition, the effect of pasteurization or sterilization on the antioxidant capacity of milk was studied. Material and Methods: The antioxidant activity of 14 different samples of cow, buffalo, goat, sheep and camel milk either raw or heat-treated by pasteurization or sterilization was investigated using DPPH radical scavenging activity, metal chelating activity and reducing power. Results: The results showed that sheep milk exhibited the strongest DPPH radical scavenging and metal chelating activities, while buffalo and sheep milk presented had the highest reducing power. Antioxidant activity of all milk fractions was lower than that of whole milk. Moreover, skim milk had the highest antioxidant capacity, while deproteinized milk was the lowest. Pasteurization did not affect the antioxidant activity of different types of milk. Sterilization led to increase the antioxidant activity of milk from different species. Conclusion: These findings indicated that sheep and buffalo milk showed the greatest antioxidant properties compared to other types of milk. Also, pasteurization did not affect the antioxidant activity of milk, while sterilization had positive effect on the antioxidant activity.