Antioxidative factors in milk

Lipid auto-oxidation in milk is affected by a complex interplay of pro- and antioxidants. Several of these compounds are also important nutrients in t he human diet and may have other physiological effects in the gastrointesti nal tract and other tissues. Among antioxidative enzymes superoxide dismuta se catalyses the dismutation of superoxide anion to hydrogen peroxide. The degradation of hydrogen peroxide can be catalysed by catalase and the selen oprotein glutathione peroxidase. The latter enzyme can also degrade lipid p eroxides. Lactoferrin may have an important role by binding pro-oxidative i ron ions. The occurrence of different forms of these antioxidative proteins in milk and available data on their functional role are reviewed. More rem ains to be learnt of individual compounds and as an example the potential r ole of seleno compounds in milk is virtually unknown. Antioxidative vitamin s in milli can provide an important contribution to the daily dietary intak e. Moreover vitamin E and carotenoids act as fat-soluble antioxidants, e.g. in the milk fat globule membrane, which is regarded as a major site of aut o-oxidation. Vitamin C is an important water-soluble antioxidant and intera cts in a complex manner with iron and fat-soluble antioxidants. The concent rations of these compounds in milk art: affected by cow feeding rations and milk storage conditions. Since milk contains a number of antioxidants many reactions are possible and the specific function of each antioxidant canno t easily be defined. There are indications that other compounds may have an tioxidative function and measurement of total antioxidative capacity should be a useful tool in evaluating their relative roles.