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The effect of Kraft lignin (KL) on wheat gluten (WG) network formation during biomaterial processing was investigated. Gluten plasticized with glycerol was blended with a variable content of KL and processed into material by mixing and hot molding. The effect of KL on WG cross-linking was assessed by size-exclusion chromatography coupled with specific detection of KL by fluorescence. Whereas processing of WG usually results in cross-linking and solubility loss, KL addition promoted an increase of gluten protein solubility in sodium dodecyl sulfate buffers. The feature demonstrates that KL functional groups hinder WG aggregation. A radical scavenger activity of KL toward the thiyl radicals produced during gluten mixing is proposed. Mixing also promotes the association of KL with WG as evidenced by the coelution of KL and WG in size exclusion high-performance liquid chromatography. Finally, gluten aggregation and cross-linking can be obtained by immersion of the materials in a dioxane-water solution, thereby demonstrating the occurrence of stabilized radicals on WG material mixed with KL.

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 objective 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 A degrees 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

The industrial production of wheat gluten (WG)-based biomaterials implies to improve their actual mechanical properties as well as to reduce their water sensitivity. In this study, the effect of Kraft lignin (KL) content on the processability and on the physical properties of WG materials was investigated. WG plasticized with glycerol was blended with KL, and processed into materials by mixing and thermomolding. Materials were characterized by dynamic mechanical thermal analysis, tensile test, and water absorption measurements. The introduction of KL in plasticized WG resulted in an increase of the material glass transition temperature (Tg) and in a strong decrease of the rubbery storage modulus, which will favor industrial processing. The increase in Tg did not follow a simple mixing rule, demonstrating specific interaction between KL and WG. The resulting materials effectively showed improved properties when compared with pure WG-based materials: they exhibited higher tensile strength and lower water sensitivity in ambient conditions. (c) 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 201

The main drawbacks of protein-based bioplastics are a high sensitivity to water, insufficient mechanical properties, and a narrow window of processing conditions. The objective of this work was to study the effect of Kraft lignin (KL) on protein aggregation, functional, and rheological properties of fish protein (FP)-based bioplastic. FP powder was blended with 30% glycerol and 0-70% KL. Then, blends were thermoformed by compression molding. KL addition increased protein solubility in sodium dodecyl sulfate buffer, indicating a decrease of protein molecular weight. An introduction of KL in protein blend increased mechanical properties and decreased water absorption of materials. KL addition resulted in a decrease in storage modulus in rubbery state of protein blends. It also resulted in a decrease in viscosity of protein blends at processing temperature, as determined by capillary rheometry. Therefore, KL is an alternative additive to enlarge the protein thermal processing window and improve functional properties of FP-based materials. (c) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 201

Abstract The objective of this study was to develop a bioplastic from industrial by-products. Commercial defatted rice bran (DRB) was extruded with 0–30% kraft lignin (KL) as a filler and 30% glycerol as a plasticizer. Firstly, the effect of extrusion temperature on the plasticized DRB’s processability was determined. Increasing the die extrusion temperature from 100°C to 150°C improved the extrudability by decreasing the die pressure and motor current. Subsequently, the effect of KL on plasticized DRB was studied. The addition of 10–30% KL improved DRB processability. The addition of 30% KL markedly lowered the die pressure in comparison to using a 150°C extrusion temperature. Moreover, KL addition decreased DRB viscosity determined by a capillary rheometer. These results were coherent with a decreased storage modulus in a rubber state and an increased tan δ height determined by a dynamic mechanical thermal analyzer (DMA). However, n values of DRB with 10–30% KL could not be explained by a simple mixing rule. This may be attributed to the interaction between DRB and KL, as shown by Fourier transform infrared (FTIR) spectra. KL addition increased Young’s modulus and the glass transition temperature (Tg) of plasticized DRB. Therefore, blending DRB with KL is an effective way to improve polymer flowability at the processing temperature and mechanical properties at ambient temperature.