BS 4285-2.5:1989

Foreword
Methods
1. Scope
2. Definitions
3. Principle
4. Method A. Direct microscopic count technique
5. Method B. Direct epifluorescent filter technique
    (DEFT)
6. Test report
Table
1. Microscope factors
2. Quantities of sample, trypsin and surfactant
    solutions for test

Two methods: A for total counts in milk and B (direct epifluorescent filter technique) for total counts and counts of \'active bacteria\' in milk and other samples.

This Section of BS 4285 describes two methods of general application for the direct enumeration of bacteria:

1. method A: direct microscopic count technique for total counts in milk;
2. method B: direct epifluorescent filter technique (DEFT) for total counts or counts of bacteria in milk, certain milk products and samples such as rinses.

NOTE 1. In samples (including plant rinses) that have received some degree of heat treatment (equivalent to pasteurisation or greater), certain organisms, particularly Gram-positive cocci, will fluoresce orange (i.e. as active) but will be non-viable by plate count methods. Therefore great care is needed in interpreting results using such samples.

NOTE 2. The titles of the publications referred to in this standard are listed on page 5.