Food sampling

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Food sampling is a process used to check that a food is safe and that it does not contain harmful contaminants, or that it contains only permitted additives at acceptable levels, or that it contains the right levels of key ingredients and its label declarations are correct, or to know the levels of nutrients present.

A food sample is carried out by subjecting the product to physical analysis. Analysis may be undertaken by or on behalf of a manufacturer regarding their own product, or for official food law enforcement or control purposes, or for research or public information.

To undertake any analysis, unless the whole amount of food to be considered is very small so that the food can be used for testing in its entirety, it is usually necessary for a portion of it to be taken (e.g. a small quantity from a full production batch, or a portion of what is on sale in a shop) – this process is known as food sampling.

In most cases with food to be analysed there are two levels of sampling – the first being selection of a portion from the whole, which is then submitted to a laboratory for testing, and the second being the laboratory's taking of the individual amounts necessary for individual tests that may be applied. It is the former that is 'food sampling': the latter is analytical laboratory 'sub-sampling', often relying upon initial homogenisation of the entire submitted sample.

Where it is intended that the results of any analysis to relate to the food as a whole it is crucially important that the sample is representative of that whole – and the results of any analysis can only be meaningful if the sampling is undertaken effectively. This is true whether the 'whole' is a manufacturer's entire production batch, or where it is a single item but too large to all be used for the test.

Factors relevant in considering the representativeness of a sample include the homogeneity of the food, the relative sizes of the sample to be taken and the whole, the potential degree of variation of the parameter(s) in question through the whole, and the significance and intended use of the analytical result.