NF ISO 7402

ISO 21528-1:2004 specifies a method, with pre-enrichment, for the detection of Enterobacteriaceae. It is applicable to products intended for human consumption and the feeding of animals, and environmental samples in the area of food production and food handling. Enumeration is carried out by calculation of the most probable number (MPN) after incubation at 37 °C in liquid medium. This method is applicable when the microorganisms sought are expected to need resuscitation before enrichment, and when the number sought is expected to be in the range 1 to 100 per millilitre or per gram of test sample. A limitation on the applicability of ISO 21528-1:2004 is imposed by the susceptibility of the method to a large degree of variability

ISO 21528-2:2004 specifies a method, without pre-enrichment, for the enumeration of Enterobacteriaceae. It is applicable to products intended for human consumption and the feeding of animals, and environmental samples in the area of food production and food handling. Enumeration is carried out by counting colonies in a solid medium after incubation at 37 °C. This technique is recommended when the number of colonies sought is expected to be more than 100 per millilitre or per gram of the test sample.