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An overview of recent developments and current status of gluten ELISA methods.
C. DON (1), M. Tilley (2), K. Konitzer (3), P. Koehler (3). (1) CDC Foodphysica, Driel, Netherlands; (2) USDA-ARS, Manhattan, KS, U.S.A.; (3) Deutsche Forschungsanstalt für Lebensmittelchemie, Freising, Germany

ELISA methods for detecting and quantitating allergens have been around for some time and they are continuously improved. In this context, the development of gluten methods is no exception. Around the turn of the century, doubts were raised whether the existing “Skerritt-ELISA” would meet the 20 mg gluten/kg threshold for gluten-free foods (Codex). The up-side of an ELISA is that it is fast and easy-to-use not requiring sophisticated and expensive lab equipment. The down-side is its high variability and the fact that only the prolamin fraction is analytically determined so that conversion to gluten by calculation is required. It has taken some effort to improve gluten ELISAs for low relative standard deviation and limit of quantitation (≤ 10 mg/kg), especially for processed foods. The first ELISA for intact gluten in corn-based products to get AACCI approval was the R5 antibody-based sandwich method 38-50.01, which has also been adopted as AOACI first action 2012.01. Method AACCI 38-55.01 was approved for partially hydrolyzed gluten in 2013, but still some discussion is ongoing on the validity of this method because no accepted reference material for calibration is available. Recently, AACCI approved method 38-52.01, a G12 antibody-based sandwich ELISA for intact gluten in rice-based products. Currently, an interlab study of the R5-based lateral flow device (LFD) is in progress with the Protein & Enzymes Technical Committee, and the evaluation of the G12-based LFD starts in 2014. The advantage of LFDs is the ability to make quick on-the-spot assessments on undesirable gluten contamination in gluten-free production facilities. To date, modern ELISAs are useful and trustworthy for gluten management programs, with sufficient sensitivity (< 4 mg/kg). The ‘new kid on the block’ is an aptamer binding assay which is reported to be 6 times more sensitive than current ELISAs.

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