Abstract
A modified Sanders and Sager method was used to determine phosphatase activity in raw milk. During one complete lactation period, milks from individual cows varied from 119 to 4380 /xg phenol/0.5 ml of milk. Enzyme concentration was related inversely to milk yield, but no correlation was seen between phosphatase and breed, fat percentage, or feed. During one year, the phosphatase activity of pooled milks, representative of 500 cows, ranged from 950 to 1700 gamma phenol. Such variations could influence the heat treatment required to inactivate the enzyme to the Sanders and Sager pasteurization standard.