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

Joshua P. Taylor, University College Cork, Cork, Ireland; Fritz Jacob, Research Center Weihenstephan for Brewing and Food Quality, Technische Universität München, Freising-Weihenstephan, Germany; and Emanuele Zannini and Elke K. Arendt (1), University College Cork, Cork, Ireland. J. Am. Soc. Brew. Chem. 75(3):262-268, 2017.

(1) Corresponding author. Phone: +353 214902064. E-mail: e.arendt@ucc.ie

​Barley malt contains hordein proteins, which gluten-sensitive consumers cannot tolerate. Beer produced from barley malt also contains hordeins. 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. Keywords: Low hordein beer, Gluten-free beer, AN-PEP, Enzyme treated malt, Prolyl endoprotease, Low-gluten beer