Extrusion Processing of Wheat Gluten Bioplastic: Effect of the Addition of Kraft Lignin

Abstract

Plasticized wheat gluten (WG) was extruded with 0-50 wt% Kraft lignin (KL) contents using a co- rotating twin screw extruder with circular die. The objec- tive of this study was to evaluate the effect of KL on the extrusion processing, and on the resulting properties of those new materials. The addition of either 30 or 50 wt% KL which is a radical scavenger allowed increasing the extrusion die temperature from 80 to 110 C. Moreover, the addition of 10-50 wt% KL contents improved the processability of WG in extrusion: it decreased both die pressure and residence time for all studied feed rates and screw speeds. The addition of KL induced a protein depolymerization and the association between KL and WG as evidenced by the co-elution of KL and WG in SE- HPLC. Moreover, the addition of 10-30 wt% KL improved mechanical properties and reduced the water absorption of WG-based material.