Effect of gluten on the properties of ternary biopolymers based on gluten, whey protein concentrate, and kaolinite

Abstract

The aim of the research was to investigate the effect of different gluten (Gl) concentration on ternary biopolymers with whey protein concentrate (WPC) and kaolinite (KAO). Distilled water dispersions of Gl (10–30%), WPC (7%), and KAO (5%) were heated at 80 °C for 30 min. The concentration of WPC and KAO was based on previous research with montmorillonite. Rheological properties of produced wet biopolymers were evaluated by dynamic rheology and ultrasound viscometry. The obtained biopolymers were dried in the thermostatic cabinet for 24 h at 45 °C. The texture was determined using the puncture test and the microstructure was analyzed by scanning electron microscopy. Surface properties of dried biopolymers were analyzed by surface wettability and roughness measurements. The increase in gluten concentration caused an increase in moduli and viscosity of the obtained wet biopolymers and in the puncture force for dry biopolymers. For the ternary biopolymer, layers with intercalation and exfoliation are observed in comparison with the biopolymer obtained without KAO. With the increasing Gl content in the biopolymer, the number of surface hydrophobic groups with carbon decreased and the number of surface hydrophilic groups increased. Higher Gl concentration produced less porous structure, although there are differences in the micro and nano-scale roughness. Water contact angle decreased with the increased Gl concentration, which is in agreement with less porous microstructure of the surface. The apparent surface free energy increased with the increasing of Gl concentration. The best plastic properties and the best shape of a pot were obtained for the ternary biopolymer with the 15% Gl concentration.