Schweizerische Normen-Vereinigung

Microbiology of the food chain - Horizontal method for the enumeration of microorganisms - Part 2: Colony count at 30 degrees C by the surface plating technique
 N SN EN ISO 4833-2

Annotation

This part of ISO 4833 specifies a horizontal method for enumeration of microorganisms that are able to grow and form colonies on the surface of a solid medium after aerobic incubation at 30 °C. The method is applicable:

a) products intended for human consumption or for animal feed;

b) environmental samples in the area of food and feed production and food handling. This part of ISO 4833 is applicable to:

1) products containing heat-sensitive organisms that are likely to form a significant proportion of the total flora (e.g. psychotropic organisms in chilled and frozen foods, dried foods, other foods that may contain heat-sensitive organisms);

2) products containing obligatory aerobic bacteria that are likely to form a significant proportion of the total flora (e.g. Pseudomonas spp.);

3) products that contain small particles that can prove difficult to distinguish form colonies in a pour plate;

4) products whose intense colour prevents the recognition of colonies in a pour plate;

5) products for which distinction between different types of colony is required as part of the assessment of food quality.

In addition to the manual spread plating technique, this part of ISO 4833 also specifies the use of a spiral plater, a rapid method of performing surface colony counts.

The applicability of this part of ISO 4833 to the examination of certain fermented food and animal feeds is limited and other media or incubation conditions can be more appropriate. However, this method can be applied to such products even though it is possible that the predominant microorganisms in these products are not detected effectively.