Towards lager beer aroma improvement via selective amino acid release by proteases during mashing

Higher alcohols and esters are key compounds from fermentation that help define the character of beer. Higher alcohols are mainly produced by yeast via the Ehrlich amino acid degradation pathway of especially leucine, isoleucine, valine, and phenylalanine. Augmenting the concentration of these amino acids can enhance the output of the Ehrlich pathway. Unlike previous studies, the work reported here explores the possibility of combining endo- and exo-proteases to selectively release these amino acids to potentially impact on flavour formation. The wort from enzyme treated mash was fermented by Saccharomyces pastorianus and the green beer was analysed by GC/MS. Treatment with proteases in laboratory scale mashing increased the level of leucine, isoleucine, valine, and phenylalanine by up to twofold. Fermentation of the wort, produced about 10% more isoamyl alcohol and 17% more isoamyl acetate derived from leucine, compared to the control.