Composite food products are defined as a foodstuff intended for human consumption containing processed products of animal origin and products of plant origin. In some cases there is a need to define the amount of an animal ingredient within the product for example; to check compliance with import controls or to check QUID declarations. <P>
The aim of this project was to evaluate the use of commercially available allergen testing kits (ELISA) to determine the percentage ingredient of animal origin in composite food products. The ingredients investigated in this project were egg, milk and crustaceans (prawn and crab).
For each ingredient tested (with the exception of crab) a linear relationship was demonstrated between the amount of marker protein measured by the allergen detection kit and the percentage of the ingredient present in a simple matrix (water or wheat flour). This linear relationship was used to produce a conversion graph which then was used to convert the amount of marker protein measured in an unknown sample to the percentage of animal ingredient in a product. However, natural variation in the amount of marker proteins in milk, egg and crustaceans made accurate determination of percentage ingredient in unknown samples difficult.
During the course of the project it was clearly demonstrated that the accurate quantification of an ingredient in a sample required a standard curve produced using an identical ingredient. For example, a sample containing egg which had been heated needed to be compared to a standard curve prepared from cooked eggs. As would be expected, prawn species should be compared to an identical prawn species. This would present some problems when a composite food sample is selected for testing as it is unlikely that information on the specific raw ingredients would be available. Overall, the results show that using allergen testing kits to determine the percentage of specific ingredients present in a composite food product is not an approach that would give the degree of precision required for enforcement operations.
Find more about this project and other FSA food safety-related projects at the <a href="http://www.food.gov.uk/science/research/" target="_blank">Food Standards Agency Research webpage</a>.