Determination of the prolamin content in wort and beer
This method is suitable for wort and beer.
The ELISA test (enzyme-linked immunosorbent assay) is based on an antigen-antibody reaction. The analysis employs the R5 antibody (Mendez), which is capable of detecting up to 100 % of the prolamins derived from wheat, rye and barley. The depressions of the microtiter plate are coated with gliadin. Added to this are calibrators (a hydrolyzed mixture of wheat, rye and barley) or samples along with peroxidase coupled anti-gliadin antibodies (conjugate of the monoclonal R5 antibody). Free and immobilized gliadins compete for gliadin antibody binding sites (competitive enzyme immunoassay). Enzyme-linked antibodies not bound to the microtiter plate are removed in a final wash step. The substrate/chromogen solution is added, and the plate is incubated. The bound enzyme conjugate elicits a color change in the chromogen, and it turns blue. Adding an inhibitor or stopping reagent leads to a color change – the blue turns to yellow. The measurement is carried out photometrically at 450 nm. The absorbance of the solution is inversely proportional to the gliadin or prolamin concentration in the sample. The results are expressed in mg/kg gliadin/prolamin.