AOAC GFA Stakeholder Program Meeting Book (August 27, 2023)

ANNEX B ANNEX B PREPARATION OF MATERIALS FOR GLUTEN METHOD VALIDATION Until such time as a reference materials are available, the gluten source for all prepared test materials should be commercial, unbleached whole flours from each claimed gluten source. The chosen flour should be analyzed for Dumas or Kjeldahl nitrogen. Convert to percent crude protein by multiplying the nitrogen value by 5.83. Then convert to percent gluten by multiplying the crude protein value by the following factors, depending on the grain: Wheat 0.74 Rye 0.52 Barley 0.78 Oats* 0.15 * Oats are not regulated as a gluten source in all countries. Please see the definition of “Gluten”, and the related footnote, in the main guidance document. These conversion factors are suggestions, and may vary across different grain materials. The factors come from two publications (1,2); the conversion factors for wheat rye and barley are based on the wet chemistry method described in Wehling and Scherf (2). Method developers may also use the wet chemical method in Wehling and Scherf (2) to arrive at the gluten content for their own wheat, rye and barley flours. The use of the "wet chemical method" to determine the gluten content of wheat, barley and rye is not commercially available (at least so far). This fact could lead to frustration to method developers searching labs that provide this method.