Reduction of Hordein Content in Beer by Applying Prolyl Endoprotease to the Malting Process

Barley malt contains hordein proteins, which gluten-sensitive consumers cannot tolerate. Beer produced from barley malt also contains horde ins. Aspergillus niger prolyl endoprotease (AN-PEP) is an enzyme that has been used effectively to reduce beer hordeins during fermentation. The objective of this study was to apply AN-PEP during the steeping and germination of barley and evaluate the impact on malt quality characteristics and the hordein content of model beers. Pilot-scale malting trials were performed, and the barley was germinated for either 3 or 5 days with and without AN-PEP. Model beers were produced from malts, and the levels of beer hordeins were tested using an R5 antibody-based competitive enzyme-linked immunosorbent assay. The malt friability, extract, viscosity, and several other quality parameters were measured following industry-standard MEBAK methods. Treatment of malt with AN-PEP for 5 days resulted in a 46% reduction in beer hordeins compared with beer produced from the 5 day control malt, and the quality of the AN-PEP treated malt was comparable to untreated malt. Applying enzymes to germinating grain is a novel way to influence the levels of hordeins in barley malt beers.