Subcritical Water Treatment of Nigerian Cassava Peels for Liquefaction and Characterization

Abstract

Cassava peels are currently underutilized with about 23 million metric tons discarded annually in Africa as by-products, causing environmental pollution. However, cassava peels have been reported to consist about 50% total polysaccharides including fibers. Subcritical water treatment also referred to as hydrothermal liquefaction, which is a green technology using only water as solvent for liquefaction of compounds was employed in this study to liquefy the cassava peel. The liquefied solid was further characterized by determining the liquefaction yield, total carbohydrate, total phenol and cyanide contents. Cassava peels liquefaction yield reached 68.4% at a treatment temperature of 140°C but decreased to 38.4% at 200°C. Cassava peels liquefied at 140°C also had the highest total phenol contents. High temperature denatures total phenolic compounds, hence the resulting maximum concentration of 0.23 mg/g was obtained at 140°C. The cyanide content decreased sharply from 5.58 µg/ml at 25°C to 2.1 µg/ml at 200°C.The total carbohydrate content was also highest at a treatment temperature of 140°C. The liquefied cassava peel showed good emulsification property. These results suggest that subcritical water treatment of cassava peel can be used for liquefaction as an environmentally friendly technology and that the liquefied solid have some potential industrial applications.