Osmolyte Concentration as an Indicator of Malt Quality

Abstract

This study was conducted to test the hypothesis that malt osmolyte concentrations can be used as an indicator of barley malt quality. Barley seeds of four six-row and four two-row genotypes were steeped and then germinated for 6 days at 20°C. At intervals of 24 hr over the germination regime, green malt from each cultivar was removed, kilned, and analyzed for osmolyte concentration (OC), malt extract (ME), diastatic power (DP), α-amylase activity, soluble/total protein (S/T), and β-glucan concentration. OC increased most rapidly from days one to three of germination. After 4 days, rates of increase in OC began to slow and, after 5 days of germination, OC had plateaued or declined. In all but three genotypes, ME followed a pattern similar to that of OC, but ME levels plateaued or declined approximately 1 day sooner than OC. This suggests that OC continues to measure storage compound degradation for a longer period than ME and could be a better indicator of malt modification than ME. ME and OC were significantly and positively correlated in days two through four and day six (r = 0.740–0.927, P < 0.0001). For days two and three, OC correlated well with ME for all days (r = 0.740–0.942, P < 0.0001) and α-amylase activity for day two (r = 0.771, P < 0.0001). For day two, OC correlated well with days two through six for β-glucan concentration (r = −0.702 to −0.830, P < 0.0001). No significant correlations were found for DP and OC on any day. These data indicate that OC of malt produced at early time points in germination is a good indicator of several measures of the quality of malt produced at later time points in germination.