Activity of Arabinoxylan Hydrolyzing Enzymes during Mashing with Barley Malt or Barley Malt and Unmalted Wheat

Abstract

Pilot scale brews were prepared either with 100% barley malt (BM100) or 60% barley malt and 40% unmalted wheat (BM60W40). Arabinoxylan and β-glucan hydrolyzing enzyme activities were determined during mashing using two temperature profiles. The measured enzymic activities increased for the BM100 and BM60W40 mashes in the early stages of mashing. The endoxylanase and α-l-arabinofuranosidase activities remained constant at 50 °C but rapidly decreased above 50 °C. At 72 °C, the endoxylanase and α-l-arabinofuranosidase activities were almost completely lost. The β-d-xylosidase activity only decreased slowly at 63 °C. The β-glucanase activity decreased rapidly at 50 °C and was completely lost after 15 min at 50 °C. From the xylose (Xyl) levels (a measure for arabinoxylan content) in the BM100 worts (1.28−1.33 g/L), a solubilization of 0.23−0.26% Xyl (% of cereal dry matter) during mashing was calculated. The Xyl levels in the BM60W40 worts (0.92−1.11 g/L) corresponded with a solubilization of 0.12 to 0.15% Xyl during mashing. Keywords: Endoxylanase; xylosidase; arabinofuranosidase; β-glucanase

A novel type of arabinoxylan arabinofuranohydrolase isolated from germinated barley

“…The observed pH optimum is similar to that of other carbohydrate hydrolases synthesized by the barley aleurone during germination and secreted to the endosperm [6,40]. The enzyme is not particularly thermostable which is in agreement with the observation that arabinofuranosidase activity decreased rapidly during mashing at temperatures above 60 8C [41].…”

Preliminary evaluation of durum wheat (Triticum Turgidum Subsp Durum) during malting process

“…The degradation of the barley and wheat β‐glucans during malting and mashing is due to the action of specific enzymes, such as the β‐glucan solubilases and the endo‐β‐glucanases (endo‐1,4β‐glucanase, malt β‐glucanase, and nonspecific endo‐1,3‐β‐glucanases which hydrolyze 1,4‐β‐linkages next to a 1,3‐β‐linkage). These last endo‐enzymes were found to be inactivated after 15 min at 50°C (Debyser et al., ; Denault, Glenister, & Chau, ), but the β‐glucan solubilases are still active above this temperature (Bamforth & Martin, ). The high molecular weight β‐glucans released during the last part of the mashing are no longer degraded (Debyser et al., ).…”

“…These last endo‐enzymes were found to be inactivated after 15 min at 50°C (Debyser et al., ; Denault, Glenister, & Chau, ), but the β‐glucan solubilases are still active above this temperature (Bamforth & Martin, ). The high molecular weight β‐glucans released during the last part of the mashing are no longer degraded (Debyser et al., ). Despite the low β‐glucan levels found for all the wheat malts, no negligible endo‐β‐glucanase activities were detected (Table ).…”

“…The presence of high molecular weight NSP levels in malts can result in reduced extraction efficiency, high viscosity with consequent poor filterability, and haze formation in worts and beers (Debyser, Delvaux, & Delcour, 1998;Debyser, Derdelinckx, & Delcour, 1997;Lu & Li, 2006). Because of their high arabinoxylan content, these problems are marked when wheat or wheat malt was used as adjunct (Lu & Li, 2006).…”

A predictive model of the effects of genotypic, pre‐ and postharvest stages on barley β‐glucan levels

“…Current scientific data suggests that storage temperature varies depending on grain moisture and relative humidity due to respiration. Temperature plays a vital role in β‐glucan degradation, as the degradation is mainly dependent on the activities of endo ‐(1→4)‐β‐glucanases (cellulases) and endo ‐(1→3,1→4)‐β‐glucanases (lichenases), which are temperature‐dependent 37. Hence a lower storage temperature (<8 °C) results in greater β‐glucan stability when compared with storage at higher temperatures 38.…”