Biodegradable plastic made from bean products

The aim of the present work was to explore the suitability of two kinds of bean with typical protein quality and different starch structure to produce moulded specimens by compression. In this work we analysed the possibility of forming new plastic materials from two kinds of bean preparations; with different protein content, in the presence or absence of inherent cellulose material and other biopolymer such as starch. Significant differences were determined in the fine structure of glucopolysaccharides isolated from the different types of bean. Complete moulding of the specimens took place at 20 MPa at a temperature not higher than 140°C, for 7 min. The mechanical properties of the moulded plastics based on soluble protein black bean (BP) were superior in elongation, tensile strength and low water absorption than the soluble protein white bean (WP) variety. However, the addition of boric acid 3% (w/w, in total batch basis) to white bean plastic materials was effective in improving slightly the mechanical properties in the case of their whole flours products (WWF). The gamma radiation was effective to reduce water absorption only in plastics materials with cellulose–starch content (BWF, WWF) and improved their mechanical properties. The gelatinization process of the moulded material was influenced by the predominant lineal structure of the carbohydrate content. © 2000 Elsevier Science B.V. All rights reserved.