Addition of different polysaccharides to gluten-based biodegradable polymeric materials plasticised with glycerol/water mixtures

Abstract

The influence of adding different polysaccharides (Locust Bean Gum, Methyl Cellulose and Carboxymethyl Cellulose) to gluten-based biodegradable polymeric materials was evaluated in this work. Glycerol/water mixtures were used as plasticiser. Gluten /plasticiser and gluten/polysaccharide/plasticiser blends were prepared at different pH values by mixing at 25ºC under adiabatic conditions and subjected to thermomoulding at 9 MPa and 130ºC. Bioplastic probes were evaluated using Dynamic Mechanical Thermal Analysis, Tensile strength measurements and water absorption capacity. Results indicate that a moderate enhancement of the network structure may be achieved by adding polysaccharide, which also confers a further thermosetting capacity to the system. However, the presence of charges seems to favour phase separation between gum and protein domains, although higher compatibility was found at acidic pH. Tensile properties and water uptake capacity also exhibited a strong dependence on pH. The former were favoured by increasing pH or adding gum at the isoelectric point. The later was largely favoured when bioplastic processing was carried out at pH 3, undergoing a moderate drop when polysaccharide was added.