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The assortment and quality of bakery products designed for celiac patients may be improved by designing whole grain ingredients with low residual prolamin contents. The main objective of this study was to evaluate the extent of prolamin hydrolysis and pentosan solubilization in germinated-rye sourdoughs (GRSDs). Size-exclusion chromatography analyses, the fate of fluorescent prolamin, and immunological analyses determined the extent of prolamin hydrolysis and pentosan solubilization. Hydrolysis of rye prolamins was extensive in GRSDs, and according to enzyme-linked immunosorbent assay analyses, more than 99.5% of the prolamins were hydrolyzed. Pentosan solubilization occurred in native-rye sourdoughs, whereas in GRSDs, pentosans were partially hydrolyzed to monosaccharides. Test baking showed that the use of GRSD improved the overall quality of oat bread and that an estimated daily gluten intake from 100 g of bread would be less than 10 mg. However, the clinical safety must be assured before making any recommendations for celiac patients to use such products.

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J. Inst. Brew. 111(1), 61-64, 2005Coeliac disease is triggered by exposure to the prolamin protein fraction of wheat, barley, or rye. The prolamin content of five lager beers and one wheat beer were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblotting and seven lager beers and three wheat beers were analyzed by enzyme-linked immunosorbent assay (ELISA). Most of the lager beers were made from barley and some had varying amounts of rice or corn as adjuncts. One of the beers was "gluten-free", having been produced from corn and buckwheat without barley. The lager beer samples were gel-filtered before ELISA or SDS-PAGE analysis. Prolamin proteins were found in all but one beer which was made of corn, rice and barley and which was not the "gluten-free" beer. ELISA analysis was done using a commercially available gluten assay kit. For lager beers, a barley prolamin standard for ELISA was propanolextracted from barley malt instead of using the prolamin standard of the gluten assay kit. As expected, the wheat beers contained much higher amounts of prolamins than the lager beers. The samples were studied by SDS-PAGE to identify different prolamin fractions. Proteins having a relative molecular mass in the range of 8000-17,000 and 38,000 and above were detected in immunoblotting by the prolamin sensitive antibody in the lager beers.

The concentration of residual barley prolamin (hordein) in gluten-free products is overestimated by the R5 ELISA method when calibrated against the wheat gliadin standard. The reason for this may be that the composition of the gliadin standard is different from the composition of hordeins. This study showed that the recognition of whole hordein by R5 antibody mainly came from C-hordein, which is more reactive than the other hordeins. The proportion of C-hordein in total hordein ranged from 16 to 33% of common Finnish barley cultivars used in this study and was always higher than that of ω-gliadin, the homologous protein class in the gliadin standard, which may account for the overestimation. Thus, a hordein standard is needed for barley prolamin quantification instead of the gliadin standard. When gluten-free oat flour was spiked with barley flour, the prolamin concentration was overestimated 1.8-2.5 times with the gliadin standard, whereas estimates in the correct range were obtained when the standard was 40% C-hordein mixed with an inert protein. A preparative-scale method was developed to isolate and purify C-hordein, and C-hordein is proposed as a reference material to calibrate barley prolamin quantification in R5-based assays.

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