Alkaline phosphatase, acid phosphatase, lactoperoxidase, and lipoprotein lipase activities in industrial ewe's milk and cheese

Alkaline phosphatase activity in raw, industrial ewe's milk increased steadily >2-fold between January [1.7 units (U)/mL] and June (3.75 U/mL), whereas acid phosphatase increased 4-fold in January and February (17 mU/mL) and then remained constant until the end of lactation. By contrast, lipoprotein lipase exhibited a downward trend and lactoperoxidase decreased 2-fold during lactation. When assayed at cheese-ripening temperatures, acid phosphatase retained 16% of its activity at 37 degrees C, whereas lactoperoxidase retained between 30 and 45% of its activity at 20 degrees C. The rate of hydrolysis of model triacylglycerols by lipoprotein lipase was highest for tricaprylin. Although alkaline phosphatase in raw milk cheeses was variable from 1 to 180 days of ripening, no apparent reactivation was observed. The activity of acid phosphatase increased 2-fold during the 180 days of ripening in the cheeses made in summer, whereas in winter and spring much smaller increases were observed. Both raw milk cheeses made in summer and all pasteurized milk cheeses had very low levels of lactoperoxidase throughout ripening.