Modification of the wheat gluten network by Kraft lignin addition.

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.