Quantification of Wheat, Rye, and Barley Gluten in Oat and Oat Products by ELISA RIDASCREEN® Total Gluten: Collaborative Study, First Action 2018.15

Abstract

demonstrated performance on oat matrices, which meets the criteria as specified in SMPR 2017.021. Data from in-house validation experiments are available as Annex B to this publication. W ith a prevalence of 0.4-1.2% of the population in Europe, North America, Australia, and the Middle East (1), celiac disease (CD) is considered to be one of the most common food hypersensitivities. CD is an immunemediated inflammatory disease of the upper small intestine in genetically predisposed individuals triggered by the ingestion of dietary gluten (2). In the context of CD, gluten is defined as a protein fraction from wheat, rye, barley, or their crossbred varieties and derivatives thereof, to which some persons are intolerant, and is insoluble in water and 0.5 mol/L NaCl (3). Gluten is composed of prolamins that can be extracted by 40-70% ethanol and alcohol-insoluble glutelins that can only be extracted under reducing and disaggregating conditions at elevated temperatures. The prolamins from wheat, rye, and barley are called gliadins, secalins, and hordeins, respectively, and the prolamin content of gluten is generally taken as 50% (3). The only known effective treatment for CD is a lifelong gluten-free diet, which is based on the avoidance of gluten-containing cereals and should contain less than 20 mg gluten per day to prevent a relapse of intestinal damage (4). To guarantee the safety of gluten-free products for CD patients, a threshold of 20 mg/kg gluten for gluten-free foods is recommended by the Codex Alimentarius and legislation, for example, by the Department of Health and Human Services Food and Drug Administration in the United States (5) and by the European Commission in Europe (6). Specific and sensitive analytical methods are therefore needed for food QC. Immunochemical methods are currently recommended for the quantitative and qualitative determination of gluten in foods (3). Sandwich and competitive ELISA formats (RIDASCREEN ® Gliadin R-Biopharm R7001 and RIDASCREEN Gliadin competitive R-Biopharm R7021) based on the R5 monoclonal antibody (7) were successfully validated as AACCI Approved Method 38-50.01 for intact gluten (8) and 38-55.

Recent Progress and Recommendations on Celiac Disease From the Working Group on Prolamin Analysis and Toxicity

“…AOAC suggests low recovery rates of 60%, but the PWG feels that, in general, the recovery range should be between 80 and 120 %, which is in line with Abbott et al (161). With respect to LOD and LOQ, the three ELISAs under consideration perform well and meet the requirements (18)(19)(20)(21).…”

“…The results of the study showed recoveries ranging from 99 to 137% for wheat, rye and barley when analyzing defined validation materials (159,160) and relative reproducibility standard deviations from 10 to 53% for samples containing 10 mg/kg of gluten or higher. Following review by the AOAC Expert Review Panel for Gluten Assays, the method was adopted as AOAC Official Method First Action 2018.15 (21).…”

“…Both methods fulfill the performance requirements for gluten analysis set by the Codex Standard 118-1979 2 , i.e., a limit of quantitation of 10 mg gluten/kg or less and the detection of CD-active epitopes. The recently developed Total Gluten ELISA covers both gluten fractions and, thus, measures the gluten content (21). This is an important step forward compared to the R5 and G12 ELISAs that measure the prolamin content and this is then converted into the gluten content by multiplication with the factor of two.…”

“…Having been granted observer status at Codex Alimentarius in 1999, the PWG plays a leading role in the development of enzyme-linked immunosorbent assays (ELISA) for gluten analysis (17) and the validation of such methods in collaboration with the Cereals & Grains Association [formerly known as AACC International; (18)(19)(20)], and AOAC International (21). It also produced the only well-characterized reference material, the socalled PWG-gliadin (22) that is used to calibrate a variety of gluten analytical methods and is available in 100 mg batches from the Association of Cereal Research (Arbeitsgemeinschaft Getreideforschung e.V., Detmold, Germany).…”

A Portable Gluten Sensor for Celiac Disease Patients May Not Always Be Reliable Depending on the Food and the User

“…Gluten content was obtained by multiplying the prolamin content by a factor of 2, as stated in the Codex ( 3 ). Homogeneity of selected samples (meatball, wheat, at 20 mg/kg of gluten) prepared to be homogeneous and inhomogeneous, respectively, was tested using ten replicates from different parts of the sample container according to standard procedures ( 16 ). Mean values, absolute standard deviations and relative standard deviations (RSD) were calculated for all quantitative results.…”