抄録
Using ESR, a weak signal identified as the ascorbate free radical was observed in fresh cow's milk. The signal was unchanged after storage at 5°C for 24 h but disappeared after storage at 25°C. A marked increase in the steady-state ascorbate radical concentration was observed with the addition of H2O2, or xanthine; the increase was abolished in the presence of azide. Based on the xanthine-oxygen reductase activity and 2, 2'-azino-di-(3-ethylbenz-thiazoline-6-sulfonic acid)peroxidase activity, cow's milk contains 0.45 μM xanthine oxidase and 0.32 μM lactoperoxidase. The results suggest that H2O2- and xanthine-induced ascorbate radical formation was due to the ascorbate peroxidase activity of lactoperoxidase in cow's milk.
