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The results of an inter-laboratory study with five commercially available peanut ELISA test kits to detect and quantify peanut residues in two food matrices (biscuit and dark chocolate) at four different concentrations (0-10 mg peanut kg(-1) matrix corresponding to about 0-2.5 mg peanut protein kg(-1) matrix) are reported. In general the five ELISA test kits evaluated could detect peanut protein in the two food matrices. In three cases, the study challenged the test kits beyond their intended use for quantification below the manufacturers' defined cut-off limits. Generally, all five ELISA test kits performed well in the concentration range 5-10 mg kg(-1) rather than in the low concentration range (2.0 or 2.5 mg kg(-1)). The variation in the found recoveries of peanut between the different test kits had a spread of 44-191% across all concentrations. The quantification characteristics between test kits differed significantly at the very low mg kg(-1) level. Two test kits performed well even at concentrations below 5 mg kg(-1) with reproducibilities of 27-36% for biscuits and 45-57% for chocolate.

Undeclared peanut allergens as contaminants in foodstuffs represent a major health problem for sensitized persons. Various immunochemical techniques are employed to detect and quantify peanut allergens. There is an urgent need to compare and standardize those test systems to enable comparable allergen analyses of foodstuffs, comparable studies, and consequent and consistent measures against the presence of hidden peanut allergens. The present study compared commercially available peanut ELISA kits with human sera-based immunoassay techniques (dot blotting and Western blotting), enabling semiquantitative and quantitative detection, and identification of peanut contaminants in foodstuffs. Additionally, the effect of conventional roasting conditions on the detection and quantification of peanut with the selected methods was investigated.