Comparison of two wheat bran extracts in the sheet extrusion process

Abstract

In this study the applicability of two differently purified crude wheat bran extracts for sheet manufacturing was evaluated. The sheet extrusion was chosen for material production because it is an industrially feasible large-scale process. The wheat bran extracts had different starch (45% and 11%) and protein (18% and 38%) contents but similar arabinoxylan (16% and 17%) and lignin (11% and 12%) contents. Glycerol, sorbitol, and their blends were used as external polyol plasticizers to enhance the continuous formation of the sheet during the process. With the chosen extrusion parameters, cohesive 100-mm-wide sheets were successfully produced with single screw extruder. The mechanical and thermal properties of the sheets were evaluated, as well as their water sensitivity. Sorbitol plasticization made the sheets stronger and stiffer and significantly lowered the water vapor permeability (WVP) and water vapor sorption (WVS) of the sheets as compared to glycerol plasticization. The sheets rich in starch had a higher tensile strength and elongation at break and a lower WVP and WVS than sheets with low starch content and high protein content. The strongest and stiffest sheet with the lowest WVP was the sorbitol-plasticized sheet with high starch and low protein content.