Extruded/injection-molded composites containing unripe plantain flour, ethylene-vinyl alcohol, and glycerol: Evaluation of mechanical property, storage conditions, biodegradability, and color

摘要

Extruded/injection-molded composites of excellent mechanical property were produced from plantain flour (PF) blended with ethylene-vinyl alcohol (EVA) and glycerol. Scanning electron microscopy (SEM) revealed that composites had a smooth surface, indicative of an excellent compatibility between PF, EVA, and glycerol. Generally, tensile strength (TS), elongation at break (%E), and the displacement (DM), all decreased with increased PF content in the composite accompanied by an increase in Young's modulus (M). The composites with higher PF contents (60% or higher) had more stable mechanical properties. Selected composites (60% PF content) stored at -20°C and 4°C for 40 h showed only minor changes in mechanical properties compared with controls (23°C). However, samples stored for a similar period at 80°C were drastically altered in their mechanical properties resulting in huge increases in TS and M and a 10-fold decrease in the %E. Samples prestored at various relative humidities (RHs) for 40 h exhibited only slight decrease in TS and M and a concomitant increase in the %E with increased RH. Interestingly, sample prestored at both -20°C and 80°C exhibited significantly higher rates and extents of degradation. SEM analysis of samples left in compost for 8 weeks showed a rapid surface erosion and material deterioration with time. Evaluation of the color produced during heat processing of starch in PF as a result of Maillard reaction showed an increase in the values of luminosity (L*), chroma (C*), and hue angle (h*) with decreased PF content in the composite.