Comparative study on the properties of films based on red rice (Oryza glaberrima) flour and starch

Abstract

Biodegradable films based on red rice flour (RRF) and red rice starch (RRS) with glycerol as plasticizer were developed and formulated with different RRF:RRS ratios (10:0, 9:1, 7:3, 5:5, and 0:10, w/w). The mechanical, physicochemical, barrier, optical, antioxidant, and biodegradability properties were evaluated. The morphology, thermal stability, and protective effect of the films against sunflower oil oxidation were investigated only for selected films. The films had interesting results for moisture content, solubility, water holding capacity, water vapor permeability, color, and light transmission. Among the films studied, RRF-RRS (9:1) film showed improved mechanical properties and lower cost compared with rice-starch-based film. The films exhibited great activity in scavenging the DPPH radical (>90%). Regarding biodegradability, all films lost around 60% of weight after 15 days in soil degradation analysis. The selected RRF-RRS films (10:0, 9:1, and 0:10) were thermally stable until approximately 150 °C. SEM analyses revealed that flour-based films have less smooth surfaces and that the incorporation of starch improved their homogeneity. The RRF-RRS (9:1) film exhibited an interesting protective effect of sunflower oil and retarded its oxidation process. Therefore, this study suggests that red rice flour and starch are promising raw materials with potential to be used as active food packaging.