Evaluation of Starch Biodegradable Plastics Derived from Cassava and Their Rates of Degradation in Soil

Abstract

Starch derived from two cassava cultivars, one with high amylose (TMS 92/0325) and the other with high amylopectin contents (TMS 91/02324), were screened for their ability to produce biodegradable plastics using different compositions of plasticizers and other materials. The rate of degradation of the bioplastics produced was equally evaluated. It was observed that the degradation values for bioplastics derived from TMS 92/0325 were 70.0%, 85.4%, 90.2% and 98.6%, while those from TMS 91/02324 were 72.4%, 86.6%, 93.5% and 99.2% at the end of 7 weeks for products containing 45%, 60%, 75% and 90% of starch, respectively. This is an implicit indication that the rate of degradability of the bioplastics produced from cassava does not depend on the level of amylose and amylopectin in the starch per se but rather on the amount of the starch itself that is used in the formulation. Moreover, our results equally demonstrated that bioplastics produced from the starch derived from cultivar TMS 91/02324 had a higher tensile strength than those gotten from cultivar TMS 92/0325. Taken together, these results are suggestive of the fact that though bioplastics produced from starch having a higher amylopectin level would have a higher tensile strength, however, they do not necessarily have a faster and greater rate of degradation when composted.

Key words: Amylopectin, bioplastics, cassava starch, degradation, environment, sorbitol