Arabinoxylan Composition in Barley, Malt, and Beer

Arabinoxylans comprise 4–8% of the barley kernel and are major constituents of both aleurone and endosperm cell walls. They are partially water soluble, high-molecular-weight polymers that contribute to viscosity. Both arabinoxylan and β-glucan content of barley were found to be significantly related to beer viscosity. Therefore, arabinoxylan may be involved in some of the undesirable effects normally attributed to the β-glucans in the brewing process. A study was made of three malting barley samples to determine the composition of non-starch polysaccharide (NSP) fractions, total and insoluble, and to observe the change in their content during both commercial malting and pilot-brewing. The NSP fractions were isolated by a combination of enzyme treatments and fractional precipitation and then analyzed by gas chromatography. The NSP fractions were significantly (P < 0.05) decreased during malting and brewing. Arabinose and xylose, at a ratio of 0.70–0.72, accounted for 70% of total NSP in pilot-brewed beer. Thus highly substituted arabinoxylan alone, or synergistically with β-glucan, could result in lautering and/or filtering problems during brewing. Further investigations on the structural characteristics of arabinoxylan in barley, malt, and beer are a priority.