Submitted to: Journal of American Society of Brewing Chemists
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/25/2006
Publication Date: 1/16/2007
Citation: Henson, C.A., Duke, S.H. 2007. Osmolyte concentration as an indicator of malt quality. Journal of American Society of Brewing Chemists. 65(1):59-62. Interpretive Summary: The quality measure of malting barley that determines the basis of market value is "extract", which is simply the amount of solids that are extracted in water. Maltsters and brewers value extract because these water-soluble compounds are consumed by yeast during fermentation and some are converted to alcohol. The work reported here is of a novel, quick and reproducible method of measuring extract that requires a minimal sample volume. This method has further value because it can be used to predict extract values of malts at the end of the malting process from the measure of seeds at early stages of the malting process. This new measure of extract should be useful to maltsters and brewers as they monitor the malting process and to barley researchers studying the genetics and physiology of malting quality.
Technical Abstract: This study was conducted to test the hypothesis that malt osmolyte concentrations can be used as an indicator of barley malt quality. Seeds of four 6-row and four 2-row genotypes were steeped for six days at 20C for 6 days. At intervals of 24 h during the steeping regime green malt from each cultivar was removed and tested for osmolyte concentration, malt extract (ME), diastatic power (DP), alpha-amylase activity, soluble/total protein (S/T), and beta-glucan concentration. Osmolyte concentrations increased most rapidly in days 1 through 3 of germination. After 4 days osmolyte concentrations began to plateau. Significant positive correlations were found for malt extract and osmolyte concentrations in days 1 through 4 and day 6 (r=0.740 to 0.942, P<0.0001). Days 2 and 3 osmolyte concentrations correlated well with ME for all days (r=0.740 to 0.942, P<0.0001) and alpha-amylase activity for day 2 (r=0.771, P<0.0001). Day 2 osmolyte concentration correlated well with days 2 through 6 for beta-glucan concentration (r=-0.702 to -0.830, P<0.0001). No significant correlations were found for DP and osmolyte concentrations on any day. These data indicate that osmolyte concentrations at early time points in steeping are good indicators of several measures of malt quality at later time points in steeping.