This part of ISO 11816 - IDF 155 specifies a fluorometric method for the determination of alkaline phosphatase activity in cheese. This method is also applicable to soft cheeses and semi-hard cheeses for distinguishing raw milk cheeses from cheese produced with pasteurized milk, provided that the mould is only on the surface and not also in the inner part (e.g. blue-veined cheeses). This method can also be used to check the proper pasteurization of cheese or its raw material. In large hard cheeses where the whey curd mixture is scalded at temperatures above 50 oC, high temperatures remain for a relatively long time. This is especially the case in the centre of these cheeses, thus promoting phosphatase inactivation. To distinguish, therefore, between hard cheeses from raw milk and hard cheeses from pasteurized milk using this method requires a specific sampling technique for the cheese (see Clause 7).