Biodegradable compositions comprising starch and polysaccharide esters

The biodegradable heterophase compositions comprise partially or completely destructurised and/or complexed starch, a polysaccharide ester and a plasticizer for the polysaccharide ester. In these compositions, the polysaccharide ester constitutes the matrix and the starch the dispersed phase in the form of particles or domains of numeric mean dimension lower than 1 mum and preferably than 0.5 mum for at least 80% of the particles. The compositions also comprise an additive which can increase and maintain at values of 4 or more the pH of a solution obtained by placing the compositions in pellet form in contact with water at ambient temperature for 1 hour, with the use of a pellet:water ratio of 1:10 by weight.