Antioxidant starch composite films containing rice straw extract and cellulose fibres.

Antioxidant aqueous rice straw (RS) extract was obtained by a combined ultrasound-reflux heating process and cellulose fibres (CF) were purified by bleaching the extraction residue. Both fractions were incorporated into corn starch to obtain films by melt blending and compression moulding. CF (at 3 % wt.) greatly increased the elastic modulus (by 200 %) and tensile strength at break (by 100 %) while reducing film stretchability. Films with CF exhibited the greatest barrier capacity to water vapour and oxygen. The incorporation of RS extract (at 4, 6 and 8 % wt.) plasticised the film's amorphous phase, but also reinforced the matrix to a certain extent. The active films showed a high degree of UV absorption and DPPH radical scavenging capacity. Mono-dose sunflower oil bags were obtained with films with CF and RS extracts that, to a great extent, prevent oil oxidation in an accelerated oxidative test under UV radiation throughout 50 days.