scope:

This part of ISO 11866-IDF 170 specifies a combined method for the enumeration of presumptive Escherichia coli and of presumptive coliforms by means of a culture technique involving a liquid medium with MUG, and calculation of the number of presumptive Escherichia coli and/or coliforms per gram or per millilitre by the most probable number (MPN) technique after incubation at 30 °C. It is a more rapid method than that described in ISO 7251 as the incubation time is reduced (omission of several enrichment steps). 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 preferred for samples in which comparatively low numbers of presumptive Escherichia coli and/or other presumptive coliforms (less than 100 per gram or 10 per millilitre) are suspected.