In order to prepare a starch-based composition usable for the production of articles of biodegradable plastics material, a starch is mixed in a heated extruder with a high-boiling plasticizer and a destructuring agent for a time sufficient to cause the starch to be destructured, in dependence on the destructuring agent used, at a temperature below the boiling point of the plasticizer used and between 120.degree. and 170.degree. C.
The composition thus obtained is particularly suitable for the formulation of polymer mixtures with polymers which have relatively high melting points, since it can be processed at temperatures higher than 120.degree. C. and is suitable for extrusion at low pressure with these polymers. In particular, compositions thus obtained and mixed with polyvinyl alcohol and/or ethylene vinyl alcohol are suitable for the formation of films by blow-extrusion, since they have the desired characteristics of mechanical strength and resistance to tearing and perforation, or for the formation of articles finished by injection moulding, thermoforming or blowing.