Thermo-mechanical processing of sugar beet pulp. I. Twin-screw extrusion process

Sugar beet pulp (SBP) is the raffinate of sugar extraction. Composed of empty vegetal cells, three quarters of it consist of polysaccharides. As it is cheap and produced in great quantities SBP is a potential raw material for industrial applications other than cattle feeding. Twin-screw extrusion modified its structure and destructuring level depended on the specific mechanical energy provided (SME). By gradually increasing this energy, the rate of soluble matter increased, cell structure was progressively destroyed and SBP rheological behaviour was modified. For an SME of 745 W h kg−1, SBP examined through a scanning electron microscope showed a structure similar to that of a composite formed by a continued matrix consisting mainly of pectin and hemicelluloses filled with cellulose microfibres. Plasticized SBP was then formed by injection-molding. Thus treated, SBP becomes a cheap alternative to the use of thermoplastic starch for the production of biodegradable materials.