Fractionation-reconstitution studies to determine the functional properties of rye flour constituents

Abstract

Rye flour was fractionated into starch, protein, water-extractable (WE), and water-unextractable (WU) arabinoxylans (AX). For protein isolation a novel method was developed consisting of extraction of rye flour at pH 9.5 and 50 °C followed by dialysis under slightly acidic conditions. Flours containing different amounts of these fractions were recombined; doughs were mixed and analyzed for their rheological behavior in order to get insight into the role of the different fractions on the dough properties. WEAX decreased the elastic properties of the doughs compared to the control dough, whereas WUAX led to an increase. In doughs containing both AX fractions the effects compensated each other. The onset of starch gelatinization in the reconstituted doughs and the difference to the temperature of complete gelatinization was strongly affected by the composition of the doughs. However, the role of the protein fraction on the elastic properties of the dough and on starch gelatinization remained unclear.