This part of ISO 11866|IDF 170 specifies a method for the enumeration of presumptive Escherichia coli by means of a colony-count technique at 44 °C. The method is applicable to — milk, liquid milk products, — dried milk, dried sweet whey, dried buttermilk, lactose, — acid casein, lactic casein and rennet casein, — caseinate and dried acid whey, — cheese and processed cheese, — butter, — frozen milk products (including edible ices), and — custard, desserts and cream. The method specified in this part of ISO 11866|IDF 170 is the preferred method for samples in which comparatively large numbers of presumptive Escherichia coli (more than 100 per gram or 10 per millilitre) are suspected. CAUTION — Some pathogenic strains of Escherichia coli do not grow at 44 °C.