Antioxidant poly (lactic acid) films with rice straw extract for food packaging applications

Antioxidant PLA films incorporating 2%, 4% and 6% of phenol-rich extract from rice straw (RS) were obtained by melt blending and compression-moulding. Aqueous RS extract was obtained by a combined ultrasound-reflux heating method and characterised as to its total phenolic content (TPC) and antioxidant capacity. The effect of the extract ratio on the functional properties of the films was analysed, as well as the release kinetics of antioxidants in food simulants (ethanol 10% and 50%). Extract incorporation slightly reduced the strength of the polymer matrix, stretchability, resistance to break, barrier capacity and thermostability, while films became brownish and gained antioxidant capacity. Phenolic compounds from the extract were effectively released into food simulants, depending on the extract concentration, the food simulant and contact time. The radical scav-enging capacity of the films reached asymptotic values from about 150 h contact time, and films with 6% of the extract exhibited similar values for both simulants. So, PLA films with approximately 6% of extract could be used as biodegradable active packaging material with antioxidant capacity in both aqueous foods (simulant A) and more fatty products (simulant D1). Further studies are required to verify the antioxidant efficiency of the films in real foods.