Detection of Gluten by Commercial Test Kits: Effects of Food Matrices and Extraction Procedures

摘要

To investigate the effects of food matrices and extraction procedures for different test kits used for determination of gluten, six commercially available test kits were evaluated: R-Biopharm RIDASCREEN R Gliadin, RIDASCREEN R FAST Gliadin, RIDAQUICK Gliadin, Neogen Veratox R for Gliadin, Tepnel BioKits Gluten Assay kit, and Morinaga Wheat Protein ELISA kit. The food matrices used were gluten-free guar gum and high-fiber bread mix, also spiked with different concentrations of gluten standard reference material (SRM 8418) obtained from National Institute of Standards and Technologies (NIST). In addition, 30 gluten-free samples were surveyed for gluten content. A homogeneity study showed that spiked gluten reference materials were evenly distributed in food matrices. Because sample extraction mixtures used by the kits are different, extraction efficiencies were carefully evaluated, especially for Neogen and R-Biopharm kits, which provide the same two options for sample extraction, aqueous alcohol and cocktail buffer. Results obtained with the six assay systems and extraction procedures differed considerably. Extraction with cocktail gave almost two times higher concentration of gluten than that from ethanol extraction using RIDASCREEN kits. Further investigation of the kits resulted in divergent findings. Depending on test methods or extraction procedures used, false positives and negatives were observed.