Tracking the Progress of Congress Mashing with Osmolyte Concentration and Malt Extract Value in North American Barley Cultivars and Relationships between Wort Osmolyte Concentration, Malt Extract Value, and ASBC Measures of Malt Quality

Abstract

This study was conducted to test three hypotheses: 1) barley malt osmolyte concentration (OC) would increase more rapidly during mashing than malt extract (ME); 2) OC would better discriminate between differing barley malts during mashing than ME; and 3) OC after mashing would better correlate with ASBC measures of malt quality than ME. Malts of six two-row and six six-row barley cultivars were mashed in a micromasher, and aliquots were removed for wort OC and ME measurements at six time points during a 115-min mashing regime. For all cultivars combined, over the first 55 min of mashing wort OC values increased 120% compared with 91% for ME. At the end of the mashing regime (115 min) wort OC values further increased to 132%, whereas wort ME values remained approximately the same (91–92%). This indicates that the mass of material in wort remained approximately the same after 55 min but was further degraded to lower molecular weight compounds, increasing wort molarity and, thus, OC but not ME. Steptoe, a feed barley, was separated to a much greater degree from elite malting cultivars by wort OC than by ME values throughout the mashing regime. Except for very early in mashing (5 min), there was better separation of all cultivars by OC than by ME values throughout mashing, as determined with least significant difference analysis, indicating that OC may be better than ME for judging differences in cultivar malt quality. Linear correlations of time-course mash OC versus ME values were excellent for all cultivars combined (r = 0.977, P < 0.0001) and for two- and six-row cultivars separately. Correlations of the 115-min mashing OC and ME values with ASBC malt quality measurements were considerably better for OC than for ME (e.g., wort protein [r = 0.819, P = 0.001 for OC; r = 0.407, P = 0.189 for ME]; diastatic power [r = 0.765, P = 0.004 for OC; r = 0.287, P = 0.365 for ME]; α-amylase [r = 0.737, P = 0.006 for OC; r = 0.584, P = 0.046 for ME]; and β-glucan [r = −0.0.754, P = 0.005 for OC; r = −0.0.595, P = 0.041 for ME]). This study supports all three hypotheses.