Sustainable starch biocomposite films fully-based on white rice (Oryza sativa) agroindustrial by-products

In this work, starch biocomposites fully-based on the valorization of white rice agroindustrial by-products have been produced by melt mixing. The film matrix consisted on rice flour (RF) or rice starch (RS) obtained, which was reinforced with cellulose-rich nanocrystals obtained through simplified extraction processes from rice husks (CN-RH) and rice straw (CN-RW). The presence of impurities in RF induced the re-crystallization of starch, producing more crystalline films with better mechanical performance, but greater water vapor permeability than RS. This was overcome by the addition of 15% (w/w) cellulosic nanocrystals. Moreover, the cellulosic nanocrystals increased the stiffness of the films, with the CN-RW yielding better mechanical performance due to their more homogeneous morphology and distribution within the RF matrix. Interestingly, all the RF films showed remarkable antioxidant capacity (>20% inhibition of β-carotene bleaching), highlighting the potential of less purified materials to develop sustainable food packaging with additional functionalities.