Evaluation of Lupine Proteins as a New Source of Co-Binder for Paper Coating. Solubility and Rheological Behaviour

Plant proteins from leguminous seeds are a highly interesting raw material for paper coating processes. Due to their high molecular weight and their amphotheric character they can act as binder and co-binder in paper coating formulations for offset or rotogravure papers. At present, plant proteins are used only in small amounts as the runnability on industrially used high-speed coating machines is limited. To overcome this situation, both protein isolates and protein based binders have to be evaluated regarding rheological characteristics under high-shear conditions. Solubility behaviour nd rheological characteristics will be presented. Relults are pointing out, that the solubility can be enhanced when dissociating the globulin protein fraction into sub-units with reduced molecular weight. The rheological behaviour will be discussed using standard binder formulations with varying binder content at different temperatures.