Cellulose fiber reinforced biodegradable films based on proteins extracted from castor bean (Ricinus communis L.) cake

Abstract

The aim of this study was to develop films based on proteins extracted from castor bean (Ricinus communis L.) cake, reinforced with cellulose fibers for use in agriculture, as bags for planting seedlings. The specific aims was to study the effect of fibers concentration on the mechanical properties, color, opacity, gloss, moisture, solubility in water, water vapor permeability (WVP), microstructure, thermal properties, and chemical structure through Fourier transform infrared spectroscopy (FTIR). Proteins were extracted from castor bean cake in a reactor and then freeze-dried. The cellulose fibers were dispersed in water using a high-speed stirrer. The films were produced by dehydration of film-forming solutions (FFS) prepared with the freeze-dried protein (6g/100g FFS), cross linker (5g glyoxal/100g protein), plasticizer (30g glycerol/100g protein), and fibers (0; 2.5; 5; 7.5; 10; and 12.5g cellulose fibers/100g protein). The fiber addition had no effect on thickness, humidity, solubility in water and water vapor permeability of the films. In contrast, an increase in puncture force, tensile strength and elastic modulus, and a decrease in the elongation at break were observed as a function of fiber concentration. The fiber addition also affected color, opacity and gloss of the films. Scanning electron microscopy analysis showed that the cellulose fibers were well dispersed in the film matrix, explaining its effect on the mechanical properties of the films. The analysis by Fourier transform infrared spectroscopy (FTIR) corroborated these results. The main conclusion of this study is that the load of cellulose fibers improved the mechanical properties of films produced with the freeze-dried castor bean cake protein.