ABSTRACT

The preparation of samples for analysis involves three steps: homogenization of the content and withdrawal of the analytical unit, preparation of the first dilution of the analytical unit and the preparation of serial decimal dilutions for inoculation into or onto culture media. Work inside vertical laminar flow cabinets to prevent contamination of the sample by the environment and contamination of the environment and the analyst by the sample. The analytical unit is the amount of material withdrawn from a sample to be subjected to one or more tests. Before withdrawing the analytical units, the content of the sample should be well homogenized to ensure that the portion to be removed will be representative for the material as a whole. The surface washing technique is used for taking food samples of which most microbial contamination is predominantly present or concentrated on the surface which may be immersed in an adequate diluent contained in a sterile bag.