The Use of Visual Examination for Determining the Presence of Gluten-Containing Grains in Gluten Free Oats and Other Grains, Seeds, Beans, Pulses, and Legumes

Abstract

Obtaining representative test samples for antibody-based testing is challenging when analyzing whole grains for gluten. When whole grains are ground into flour for testing, confocal microscopy studies have shown that gluten tends to exist as aggregates within the starch background, making single-sample testing inaccurate and complicating the ability to arrive at an accurate average from multiple samples. In addition, whole-grain products present a unique risk to gluten free consumers, in that any contamination is localized to specific servings rather than being distributed across the product lot. This makes parts-per-million values less relevant for whole-grain products. Intact grains, seeds, beans, pulses, and legumes offer an alternative opportunity for gluten detection, in that contaminating gluten-containing grains (GCGs) are visible and identifiable to the trained eye or properly calibrated optical sorting equipment. The purpose of the current study was to determine a Gluten Free Certification Organization threshold level for the maximum number of GCGs within a kilogram of nongluten grains sold as specially processed gluten free product and to determine the feasibility of this threshold by evaluating visual examination data from two major oat processors.

Lentils and Gluten Cross Contact

“…One of the bags contained a single grain and the other bag contained 2 grains. According to calculations published by the Gluten-Free Certification Organization, one gluten-containing grain could contain upwards of 10.5 mg of protein, including 9.45 mg of gluten (4). According to the study authors, the protein and gluten levels are based on the upper limit of published ranges (i.e., a single grain weight of 50 mg, 21% grain protein, and a gluten content as 90% of the protein content of the grain) (4).…”

“…For a product to be considered gluten-free in the United States, it must contain <20 mg of gluten per kilogram (or 20 parts per million of gluten). A product at the 20-ppm level of gluten should contain no more than 2 intact gluten-containing grains per kilogram or 35.27 (1,000 g) ounces of food (or 1 intact gluten containing grain in 17.64 ounces [500 g] of food) (4,5). Based on these calculations, a 16-ounce (454 g) bag of lentils containing 1 intact gluten-containing grain would not be considered gluten-free.…”