Characterization of rye flours and their potential as reference material for gluten analysis.

The safety of gluten-free products relies on accurate gluten analysis, most commonly using ELISA. These test kits are calibrated to gliadins or wheat gluten, because there is no reference material (RM) for rye. Our aim was to select representative samples out of 32 rye cultivars for use as RM. All cultivars were characterized by RP-HPLC, gel permeation HPLC and R5 and G12 ELISA. The protein and gluten content ranged from 5.5 to 11.2 g/100 g and 3.0 to 7.8 g/100 g, respectively. The average protein distribution was 40% albumins/globulins, 23% γ-75k-secalins, 17% γ-40k-secalins, 14% ω-secalins and 6% high-molecular-weight-secalins. The mean prolamin/glutelin ratio was 4.4 for rye and this translates to an estimated conversion factor from rye prolamins to gluten of 1.2, instead of the usual factor of 2. Seven cultivars were selected for RM production based on cluster analysis, geographical origin and availability to comprehensively cover the diversity of rye.

Development of a barley reference material for gluten analysis.

Celiac disease (CD) can be triggered in susceptible individuals by the consumption of gluten, a complex storage protein mixture present in wheat, rye and barley. There is no specific reference material (RM) available for barley and this leads to inaccurate quantitation of barley gluten in supposedly gluten-free foods. Therefore, the aim was to select representative barley cultivars to establish a new barley RM. The relative protein composition of the 35 barley cultivars averaged 25% albumins and globulins, 11% d-hordeins, 19% C-hordeins, and 45% B/γ-hordeins. The mean gluten and protein content was 7.2 g/100 g and 11.2 g/100 g, respectively. The prolamin/glutelin ratio (1:1) commonly used in ELISAs to calculate the gluten content was found to be inappropriate for barley (1.6 ± 0.6). Eight cultivars suitable as potential RMs were selected to ensure a typical barley protein composition and improve food safety for CD patients.