the foam density of starch-based products ranged between 18.7 and 30.5 kg/m3. The products were at least 2.5 times more dense than EPS-based foams. That happens because it's a large difference in density between polystyrene and starch, and a lower expansion factor. However, during the extrusion-cooking, the starch density has been reduced substantially; open cells created during expansion prevent the foam from continuing the expansion