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Both assays are comparable and robust. The repeatability and reproducibility data are in a range that is acceptable for ELISAs. Kits from both suppliers fulfilled performance criteria of regular ELISA methods, and it is shown that both ELISA kits guarantee a sensitivity of 1.5 ppm gliadin for gluten-free food.

A dessert matrix previously used for diagnosis of food allergies was incurred with pasteurised egg white or skimmed milk powder at 3, 6, 15 and 30 mg allergen protein per kg of dessert matrix and evaluated as a quality control material for allergen analysis in a multi-laboratory trial. Analysis was performed by immunoassay using five kits each for egg and milk (based on casein) and six 'other' milk kits (five based on β-lactoglobulin and one total milk). All kits detected allergen protein at the 3 mg kg(-1) level. Based on ISO criteria only one egg kit accurately determined egg protein at 3 mg kg(-1) (p=0.62) and one milk (casein) kit accurately determined milk at 6 (p=0.54) and 15 mg kg(-1) (p=0.83), against the target value. The milk "other" kits performed least well of all the kits assessed, giving the least precise analyses. The incurred dessert material had the characteristics required for a quality control material for allergen analysis.

The second generation of a competitive ELISA for prolamin quantification based on the R5 antibody was studied for method performance and suitability to detect partially hydrolyzed prolamins in food. To be able to convert signal intensities to gluten concentrations, as required by the Codex Alimentarius Standard, a new calibrator consisting of a peptic-tryptic digest of wheat, rye, and barley prolamins was used for the first time. LOD and LOQ of the assay were 1.36 and 5.0 mg prolamin/kg food, respectively. Analysis of beer samples and a hydrolyzed wheat product showed that the assay provided significantly higher prolamin concentrations, compared to the sandwich ELISA based on the same antibody, which is only suitable for the detection of intact prolamins. Spiking experiments with defined concentrations of partially hydrolyzed prolamins gave recoveries ranging from 92 to 136%.

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