Single-pass, double-pass and acid twin-screw extrusion-cooking impact physicochemical and nutrition-related properties of wheat bran

The potential of extrusion-cooking as a technique to change the physicochemical characteristics of wheat bran, and thereby its nutrition-related properties was investigated. It was investigated whether double-pass extrusion-cooking or the addition of citric acid had a larger effect than single-pass extrusion-cooking alone. Double-pass extrusion-cooking resulted in the highest strong water-binding capacity (1.37 g/g dm), while acid extrusion-cooking resulted in the lowest (0.66 g/g dm) due to hydrolysis of bran polymers that contribute to the microstructure. Double-pass and acid extrusion-cooking increased the amount of water-extractable arabinoxylan, the main dietary fiber constituent (from 0.62 % to 1.75 % and 3.11 % dm, respectively), and therefore also increased extract viscosity. An increased in vitro fermentation rate was observed for double-pass compared to single-pass extruded bran. More phytate was degraded and more ferulic acid released during double-pass extrusion-cooking as compared to acid and single-pass extrusion-cooking. In conclusion, double-pass and acid extrusion-cooking distinctly modify wheat bran physicochemical and nutrition-related properties.