Soluble corn arabinoxylan has desirable material properties for high incorporation in expanded cereal extrudates

Abstract

Incorporation of soluble dietary fiber to cereal extrudates is a practical approach to improve its nutrition values, but it can be technically challenging as a reduction in extrudate quality commonly occurs at a high incorporation level. In the present study, we incorporated soluble corn arabinoxylan (CAX) into cornmeal at a high level (25% w/w) and produced expanded extrudates with a comparable microstructure to cornmeal without added fibers. For a comparison, wheat arabinoxylan (WAX)- and long chain inulin-incorporated cornmeal extrudates had low degrees of expansion and high bulk density. CAX-incorporated cornmeal had comparable melt viscosities as the cornmeal control at shear rates higher than 100 s −1 and an endothermic transition occurring at the same temperature range (130–170 °C), both similar to cornmeal alone. On the other hand, WAX-incorporated cornmeal instead had an exothermic transition at 130–170 °C, and a substantially higher melt viscosity than cornmeal. Long chain inulin-incorporated cornmeal had two overlapped endothermic transitions at 130–170 °C and a markedly lower melt viscosity than cornmeal. The superior functionality of CAX in corn extrudates was attributed to its highly branched xylan backbone extensively substituted by complex sidechains and charged structure. CAX had a hypothesized ellipsoid-shaped conformation that presumably would not engage in intermolecular entanglements, resulting in a low viscous near-Newtonian flow behavior. In summary, addition of CAX to cornmeal did not cause major changes in melt viscosity and endothermic transition of the pre-extrusion material, nor to the quality of resulting extrudates. • Corn arabinoxylan (CAX)-incorporated (25%) cornmeal extrudates had good expansion. • CAX performed better in extrusion than wheat arabinoxylan or long-chain inulin. • CAX-incorporated cornmeal had desirable thermal and rheological properties. • Branched structure of CAX appeared to contribute to its functionality in extrusion.