Effects of multiscale rice straw ( Oryza sativa ) as reinforcing filler in montmorillonite-polyvinyl alcohol biocomposite packaging film for enhancing the storability of postharvest mango fruit ( Mangifera indica L.)

Abstract Biodegradable materials, prepared from rice straws (RS), were used as fillers in montmorillonite clay-polyvinyl alcohol (Mt-PVA) matrix in order to develop a biocomposite packaging film for determining the storability of mango fruit. The RS was treated (×3 times) with alkali sodium hydroxide (NaOH) followed by sodium chlorite (NaClO2) and acetic acid (CH3COOH) (×3 times). Subsequently, cellulose nanocrystals (CNC) were isolated by sulfuric acid (H2SO4) hydrolysis. The extracted CNC were scaled at a length (L) of 831 ± 45.0 nm and a diameter (D) of 44 ± 12 nm to obtain an aspect ratio (L/D) of 18.8. Transmission electron microscopy results showed the needle-like structures of CNC. X-ray diffraction showed that the crystallinity of the fiber increased after every treatment. Morphological observations of the untreated, treated RS fibers and biocomposites were evaluated by using field emission scanning electron microscopy. Our study suggested that the thermal stability and tensile properties of the biocomposite films significantly improved by increasing the filler concentration up to 6 wt%. Furthermore, the mango fruit sealed with packaging film exhibited a shelf life extension until 19 ± 2 d with good quality parameters (phenol, flavonoid content and DPPH antioxidant activity), reduced mass loss, increased CO2 and low O2 level. The present study revealed the efficiency of the bio-nanocomposite film for improving the storability of freshly harvested mangoes.