Studies on water-extractable arabinoxylans during malting and brewing

The most important non-starch polysaccharides in barley grain are β-glucan and arabinoxylans. Arabinoxylans are partially water-extractable, high-molecular-weight polymers that contribute to viscosity and membrane filterability. Changes to arabinoxylans content and endo-xylanase activity during germination and kilning were studied. This paper was aimed at determining the composition of total arabinoxylans and water-extractable arabinoxylans in malt and observing their changes during brewing. The water-extractable and total arabinoxylans contents of six barley malts and wheat malt varied in the range of 0.42-0.98% and 3.84-6.90%, respectively. Their l-arabinose-to-d-xylose ratio ranged between 0.49-0.59 (total arabinoxylans) and 0.60-0.85 (water-extractable arabinoxylans). Contents of arabinoxylans in worts mainly originated from the soluble part of arabinoxylans in malt. The use of rice adjunct decreased arabinoxylans contents of wort and beer. The correlation between arabinoxylans and viscosity was investigated. Results showed that water-extractable arabinoxylans in wort have positive and higher correlation value with wort viscosity than those of β-glucan in wort, and both water-extractable arabinoxylans and β-glucan in beer have significant correlation (p < 0.01) with beer viscosity.