Green Malt Osmolyte Concentration as an Early Indicator of Finished Malt Quality

Abstract

This study was conducted to test the hypothesis that barley green malt osmolyte concentration (GMOC) can be used as an early indicator of finished barley malt quality. Seeds of three two-row genotypes and three six-row genotypes were steeped and germinated in a mircomalter for 6 days. At intervals of 24 hr over the germination regime, green malt from each cultivar was both removed and tested for GMOC and kilned and analyzed for the finished malt quality measurements of malt extract (ME), diastatic power (DP), α-amylase activity, soluble protein/total protein (S/T), and β-glucan concentration. GMOC values increased most rapidly from days one to three of germination. For all but one genotype, the rates of increase in GMOC values after 3 days began to slow or plateau. ME values followed a pattern over time similar to that of GMOC; however, the rates of increase in ME levels began to slow or plateau sooner than for GMOC values. ME and GMOC values for all genotypes combined and for each genotype individually were significantly and positively correlated over the 6 days of germination (r = 0.840, P < 0.0001 [combined genotypes]; r = 0.878–0.943, P < 0.0001 [individual genotypes]). Significant correlations also were found between GMOC and other finished malt quality parameters over the 6 days of germination for all genotypes combined and for each individual genotype (α-amylase activity, DP, and S/T were positive, r = 0.757–0.856, P < 0.0001 [combined genotypes], and r = 0.737–0.944, P = 0.0006 to <0.0001 [individual genotypes]; β-glucan concentrations were negative, r = −0.851, P < 0.0001 [combined genotypes], and r = −0.788 to −0.896, P = 0.0001 to <0.0001 [individual genotypes]). GMOC values on day one were significantly and positively correlated with ME on days one through five (r = 0.756–0.886, P = 0.0003 to <0.0001) and α-amylase on days one through five (r = 0.635–0.776, P = 0.0046–0.0002). GMOC values on day two were significantly and positively correlated with ME on days one through six (r = 0.769–0.910, P = 0.0002 to <0.0001) and α-amylase activity and S/T on days three through six (r = 0.733–0.890, P = 0.0005 to <0.0001). This indicates that GMOC values from early periods in germination (days one and two) are good indicators of finished malt ME and other finished malt quality values for malt produced 1–4 days later.