Antioxidant properties of caseins and whey proteins from colostrums

The bovine colostrums collected within 7 days postpartum were used to prepare caseins and whey proteins. The caseins and whey proteins obtained by acid precipitation were freeze-dried and then dissolved respectively in 0.1 M and 0.05 M sodium phosphate buffer (pH 7.0) for electrophoresis and antioxidant activity analysis. The antioxidant activities, including reducing power, ferrous ion chelating ability, alpha,alpha-diphenyl-beta-picrylhydrazyl (DPPH) radical scavenging activity and inhibitory effect on lipid peroxidation, were measured and compared with a-tocopherol, butylated hydroxyanisole, (BHA) or ethylenediamine tetraacetic acid (EDTA, 2 Na-salt). Results showed that whey proteins at a concentration of 20 mg/mL had triple reducing power as that of the caseins. As for the ferrous ion chelating ability, both caseins and whey proteins exhibited increasing chelating ability as protein concentration increased. The whey proteins obtained from the colostrums collected on the first two days apparently exhibited relatively higher chelating ability. Similarly, DPPH radical scavenging activity of caseins and whey proteins increased as the protein concentration increased. Whey proteins from the colostrums collected between the second and the fourth days (Whey proteins 2, 3 and 4) and the caseins from the colostrums collected on the second day (Casein 2) had relatively higher radical scavenging activities, higher than 60% at a concentration of 20 mg/mL. The inhibitory effect on lipid peroxidation of caseins was higher than that of whey proteins, and was comparable to those of alpha-tocopherol and BHA within 8-hour reaction.