Osmolyte Concentration as an Indicator of Malt Quality (1). Cynthia A. Henson (2), United States Department of Agriculture–Agricultural Research Service Cereal Crops Research Unit, Madison, WI; and Stanley H. Duke, Department of Agronomy, University of Wisconsin, Madison. (1) Mention of a proprietary product does not constitute a guarantee or warranty of the product by the United States Department of Agriculture and does not imply its approval to the exclusion of other suitable products. (2) Corresponding author. E-mail: <cahenson@wisc.edu>; Phone:+1.608.262.0377. J. Am. Soc. Brew. Chem. 65(1):59-62, 2007. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. American Society of Brewing Chemists, Inc., 2007.

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), alpha-amylase activity, soluble/total protein (S/T), and beta-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 alpha-amylase activity for day two (r = 0.771, P < 0.0001). For day two, OC correlated well with days two through six for beta-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. Keywords: alpha-Amylase, beta-Amylase, Barley, beta-Glucan, Diastatic power, Malt extract