Production and application of barley malt extract with high peptidase activity for the degradation of gluten in wort

Abstract

Special malt with high gluten-specific peptidase activity was prepared by germinating barley grain for 8 days at 18 °C and 48 % humidity. Endogenous malt peptidases were characterized and used to degrade gluten in barley wort. Peptidases of aqueous malt extracts degraded celiac-active peptides by cleaving peptide bonds involving proline residues. The peptidase activity was not affected by cultivar, area of cultivation, and high temperatures up to 80 °C during kiln drying. Temperatures up to 50 °C were tolerated without loss of full activity in aqueous solution. The presence of ethanol decreased the activity significantly. Cross-flow filtration, freeze-drying, and evaporation under reduced pressure at 50 °C were used to produce a concentrated enzyme-active malt extract. The latter method yielded the best results, and the obtained concentrate was used to study gluten degradation in barley wort as affected by concentration of the extract, incubation time, and temperature. The gluten content was determined by a competitive R5-ELISA. The addition of 10 % concentrated extract (grist-to-water ratio 1:2.5; 40.4 °Brix) to wort and incubation for 24 h at 50 °C resulted in a gluten-free wort.