Xylanase induced changes to water- and alkali-extractable arabinoxylans inwheat flour: Their role in lowering batter viscosity

The effect on the viscosity of wheat flour batter following treatments with a crude pentosanase-containing enzyme preparation and an endo-xylanase pur ified from the same preparation; was studied in relation to changes to die chemical features of the water- and Ba(OH)(2)-extractable arabinoxylan frac tions. Addition to batter of the crude enzyme or the pure xylanase caused a consistent and identical decrease in batter viscosity, demonstrating that the viscosity change was caused by the selective action of the xylanase in the crude enzyme preparation. The lowering of batter viscosity upon additio n of enzyme was attributed to partial hydrolysis of the arabinoxylans in th e water-extractable fraction which lead to an increase in the proportion of lower molecular weight water-extractable arabinoxylans possessing an incre ased xylose/arabinose ratio. There was no detectable change in the monosacc haride composition of either the water- or Ba(OH)(2)-extractable arabinoxyl an fraction after enzyme treatment and no indication of any increase in the amount of the water-extractable arabinoxylan fraction at the expense of th e Ba(OH)(2)-extractable fraction. It is concluded that the xylanase can ext ensively degrade arabinoxylan to small oligosaccharides in vitro. However, such degradation does not take place in situ, in the enzyme treated batters , where only a very small shift in the molecular weight profile of the wate r-extractable arabinoxylans was necessary to effect major changes to batter viscosity. (C) 2001 Academic Press.