The combined use of hull-less barley flour and xylanase as a strategy for wheat/hull-less barley flour breads with increased arabinoxylan and (1→3,1→4)-β-D-glucan levels

Bread-making with a composite flour (CF) consisting of 60% wheat flour (WF) and 40% hull-less barley flour, increased the total and soluble (1→3,1→4)-β-D-glucan and total arabinoxylan (AX) contents of dough and bread samples, but decreased the specific bread loaf volume. A xylanase insensitive to inhibition by Triticum aestivum L. xylanase inhibitor (TAXI) and xylanase inhibiting protein (XIP), increased loaf volume by 8.8 and 20.1% for WF and CF breads, respectively. Xylanase addition not only markedly improved loaf volume of CF bread, but also increased the soluble AX content of the WF and CF dough and bread samples because of conversion of water-unextractable AX into soluble AX. The xylanase had no impact on the extractability and molecular weight of (1→3,1→4)-β-D-glucan, but (1→3,1→4)-β-D-glucan was degraded during bread-making probably because of endogenous β-glucanase activity. Taken together, the results clearly show that the combined use of hull-less barley flour and a xylanase active during bread making, lead to palatable breads with high total and soluble AX and (1→3,1→4)-β-D-glucan contents. The sum of total AX and (1→3,1→4)-β-D-glucan was 1.70% for WF bread and 3.06% for CF bread, while the sum of soluble AX and (1→3,1→4)-β-D-glucan was 0.49 and 1.41% for control WF and CF xylanase supplemented breads, respectively.