P-9
Effects of malting and mashing conditions on the molecular weights of arabinoxylan and beta-glucan in wort
Presenter: Paul Sadosky, Plant Sciences, North Dakota State University, Fargo, ND
Co-Authors: Paul Schwarz and Richard Horsley Plant Sciences, North Dakota State University, Fargo, ND

During the malting and brewing process, barley endosperm and aleurone cell walls are degraded and solubilized by endogenous enzymes. The resulting polysaccharides, arabinoxylan (AX) and beta-glucan (BG), cause processing problems mainly in the areas of liquid/solid separation and filtration. It appears that only the high molecular weight fractions are problematic. The objectives of this research were to determine the effects of malting and mashing conditions on the molecular weight profiles of wort AX and BG. Arabinoxylan and BG were isolated from wort and beer using enzymes and ultrafiltration. The molecular weight distributions of the isolated polysaccharides were determined using high-pressure size-exclusion chromatography with refractive index, laser light scattering, and viscometric detectors. Experiments were conducted as randomized complete block designs. For malting, independent variables were cultivar, germination time, germination temperature, and germination moisture. Barley growing locations were repetitions. For brewing, independent variables were mash time and mash temperature. Dependent variables for both experiments were wort AX and BG average molecular weight, percent greater than 500 kDa, percent between 50 and 500 kDa, percent less than 50 kDa, and concentration. Cultivar had a significant effect on average AX molecular weight. The interaction between cultivar and malting treatment was significant for beta-glucan average molecular weight. Cultivar was significant for both AX and BG between 50 to 500 kDa and less than 50 kDa. Germination time had a significant effect on AX average molecular weight. The trend was for decreased molecular weight with increased germination time. Simple effects showed BG average molecular weight also decreased with germination time, although the cultivars responded differently. The effects for germination time on AX and BG in the >500 and 50–500 kDa categories were significant as well, with both polymers decreasing with malting time. Both AX and BG in the <50 kDa category increased significantly with germination time. Arabinoxylan concentration increased significantly with germination time. Beta-glucan concentration responded to germination time differently by cultivar. Both AX and BG in the >500 kDa category decreased significantly with increased mash time. Mashing time was significant for BG in the 50–500 kDa category, but showed an increase with mash time. Arabinoxylan in the 50–500 kDa category did not change with mash time. In the <50 kDa category, BG decreased significantly with mash time while AX increased, but not significantly. Both AX and BG concentration increased significantly with increased mash time.

Paul Sadosky received a B.A. in psychology from Clemson University in 1991, and a M.S. in cereal science from North Dakota State University in 2000. He is a graduate of the 1995 Siebel Institute Diploma Course and worked as head brewer at Atlanta Brewing Company. As part of his M.S. program he completed a malting internship with Busch Agricultural resources in Moorhead, MN. He is currently the brewer at the Great Northern Restaurant and Brewery and a Ph.D. candidate at North Dakota State University.