How are the properties of biocomposite foams influenced by the substitution of cassava starch for its residual sources?

Abstract

Two residues from the cassava processing industry, cassava inner bark and gelatinized starch, were applied as substitutes for native cassava starch in the development of foams using a thermocompression process (180 °C, 6 min, 7 MPa). The starchy pastes were also submitted to a pre-gelatinization step in a water bath (80 °C, 2 min) to evaluate the effect of this step on the properties of the foams. The thickness measurements seemed to be more influenced by the starch amount in the formulations, while the bulk density and the water absorption capacity (WAC) were more influenced by the starch source and its chemical composition. In general, the pre-gelatinization seemed to have affected more directly the properties of the biocomposites fabricated solely with cassava starch. Moreover, these pre-gelatinized biocomposites presented greater mechanical resistance and higher elongation values. Biocomposites with the incorporation of cassava inner bark presented lower WAC (84% after 90 min), demonstrating their high potential for application as a quick-use packaging for low-moisture foods. These results showed that the non-necessity of the pre-gelatinization step could lead to an increase in biocomposites’ fabrication speed due to the elimination of the water bath heating stage, minimizing production costs. Besides that, it is important to highlight the cost reduction related to the use of cassava residues instead of native cassava starch.