Contribution of the lactoperoxidasesystem to the keeping quality of pasteurized milk The lactoperoxidase system is a naturalantimicrobial system that can play an active role in the keeping quality of raw milk.However, there is little information on the activation of the lactoperoxidase system aftermild heat treatments such as pasteurization. The keeping quality of milk pasteurized at 72C for 15 seconds has been found to be better than that of milk heated at 80 C for 15seconds. The kinetics and mechanism of lactoperoxidase action were investigated. Milkspasteurized at 72 and 80 C were stored at 8 C and the keeping quality was assessed dailyover 16 days by measuring pH, clot-on boiling, alcohol stability, total viable count,titratable acidity and dissolved oxygen. The results showed that pasteurizationtemperature is critical to the keeping quality of milk.