R5 competitive ELISA effective for fermented foods

By Van Waffle

Summary: AACC International, an organization of cereal grain specialists, collaborated with researchers to perform the first independent validation of the R5 competitive ELISA test for measuring hydrolyzed gluten protein in foods. Controversy surrounds hydrolyzed protein (see “Did you know?”), which turns up in many prepared foods. It is produced particularly by the process of fermentation, as in beer and sourdough.

ELISA (enzyme-linked immunosorbent assay) uses an antibody called R5 to measure gluten content. Two types of R5 ELISA may be used: sandwich and competitive. The R5 sandwich ELISA has served as the food industry’s standard test for gluten, but is ineffective at identifying hydrolyzed fragments. The R5 competitive ELISA is more sensitive to the small protein segments found in fermented foods, but its accuracy has not been verified until now.

The researchers prepared samples of beer, starch syrup and sourdough. Some were gluten free and some contained known quantities of gluten protein. The samples went to 16 labs across North America and Europe for testing using the R5 competitive ELISA following strict protocols to prevent contamination. The tests were able to detect gluten at levels as low as 5 parts per million (ppm) and accurately measure gluten exceeding 20 ppm, the level considered toxic for people with celiac disease.

Conclusion: AACC International declares the competitive R5 ELISA valid for testing fermented foods and beverages to determine whether they comply with gluten-free standards. However, it has yet to be accepted by American legislators.


[1] “AACCI approved methods technical committee report: collaborative study on the immunochemical determination of partially hydrolyzed gluten using an R5 competitive ELISA”, Koehler P, Schwalb T, Immer U, Lacorn M, Wehlin P, Don C, Cereal Foods World, 2013 May; 58(3):154-158.