摘要 : Activities and thermal stabilities of 5 indigenous milk enzymes, namely lactoperoxidase (LPO), N-acetyl- beta-glucosaminidase (NAGase), gamma-glutamyl transpeptidase (GGTP), alkaline phosphatase (ALP) and xanthine oxidase (XO) in ... 展开 Activities and thermal stabilities of 5 indigenous milk enzymes, namely lactoperoxidase (LPO), N-acetyl- beta-glucosaminidase (NAGase), gamma-glutamyl transpeptidase (GGTP), alkaline phosphatase (ALP) and xanthine oxidase (XO) in cows' milk, buffaloes' milk and goats' milk were determined. The activities of these enzymes in goats' milk were significantly lower than those in cows' milk or buffaloes' milk. There were large differences in activities of LPO among the milk samples tested. As compared with cows' milk, buffaloes' milk exhibited nearly 1.76-fold higher activities, while goats' milk contained nearly 8.87-fold lower activity. Goats' milk showed nearly 4-fold lower NAGase and GGTP activities as compared with either cows' milk or buffaloes' milk. Cows' milk and buffaloes' milk had similar levels of NAGase, GGTP, ALP and XO activities. It was observed that ALP and XO activities were concentrated in the cream phase; LPO and NAGase activities were higher in the skim milk phase and GGTP activity was distributed in both these phases. Thermal stability (15 s at temp. ranging from 65 to 90 degrees C) varied from enzyme to enzyme. The thermal inactivation pattern of each individual enzyme from cows' milk, buffaloes' milk and goats' milk was similar. The thermal stability of these 5 enzymes was in order of XO > LPO > (GGTP, NAGase) > ALP. It is suggested that measurement of these enzymes in processed milk can provide information on heat treatment of milk. 收起