Effects of amino acid profile, endoprotease activities and wort quality on fermentability under different malting and brewing conditions

Abstract

The quantity of alcohol produced through wort fermentation is fundamental to a malt’s quality. Good fermentability is dependent on many malt quality parameters but requirement for proteases to provide amino acids and peptides for yeast is poorly understood. The thesis investigated relationships between amino acid profiles, endoprotease activities and fermentability under different malting and brewing conditions. Methods for measuring individual wort amino acids, endoprotease activity and fermentability were modified or developed to better understand the relationships. Levels of lysine and glycine were affected the most by malting and the variability was not always well predicted by the standard FAN analysis. Cysteine endoprotease activity developed similarly to total amino acids levels but associations were not significant Amino acids were limiting to fermentability at low yeast pitching rates and with the use of high maltose syrups but malt modification was the key determinant of fermentability. Studies on non fermentable sugar content were recommended.