Cellulose fiber enhances the physical characteristics of extruded biodegradable cassava starch foams

•5% cellulose fiber correlated positively to cassava starch foam expansion.•15% feed moisture content with 250 rpm screw speed gave the greatest ER.•Smaller particle size of cellulose (<32 μm) improved expansion of the foam.•20% feed moisture content, larger size of C1 fiber (32–200 μm) did not affect ER.