Residual alkaline phosphatase activity after heat treatment of ovine and caprine milk

The objective of this work was to study the decrease of alkaline phosphatase (ALP) activity during heat treatment of ovine and caprine milk in comparison to that of bovine milk. For this purpose, different samples from the three milk kinds were subjected to heat treatment at 59 °C under different time conditions and the residual ALP activity was determined using the IDF reference method and the automated fluorimetric IDF method. The heat treatment reduced the ALP activity in bovine milk slower (P < 0.05) compared to that of the other two milk kinds, whereas the fastest decrease was observed in ovine milk. The lowest absolute values of ALP activity were observed in caprine milk before and after heat treatment. The results for ovine and caprine milk obtained by the two methods (reference and automated fluorimetric) were linearly correlated. This preliminary study indicates that the automated fluorimetric method can be used to analyze a high number of ovine and caprine milk samples taken at different stages of lactation period, with the aim to define the acceptable limits of residual ALP activity in pasteurized ovine and caprine milk.