Oxygen absorbing food packaging made by extrusion compounding of thermoplastic cassava starch with gallic acid

Abstract

Control of oxygen levels in package headspace directly preserves quality and safety of packaged foods and beverage. This research aimed to produce oxygen scavenging bio-based plastics to control oxygen contents in food packaging. Thermoplastic starch (TPS) was produced via extrusion compounding with different gallic acid (GA) contents (1–10%) and linear-low-density polyethylene (LLDPE). Morphology, relaxation behavior, surface and mechanical properties and oxygen scavenging capacities were investigated. Increasing GA content plasticized and facilitated starch melting. GA likely induced H-bonding and esterification with the TPS phase, which apparently modified mechanical relaxation behavior and interacted with LLDPE via C–H bonded aromatic rings. Increasing GA to 5% gave more homogeneous microstructures and miscible GA, while a further increase caused clumps that likely reduced surface area available for oxygen. XRD intensity of TPS/LLDPE linearly decreased with increased GA that likely led to increased water vapor permeability possibly due to decreased crystallinity of the polymers. Studies of oxygen scavenging at 4, 25 and 50 °C showed enhanced capacity with increasing temperature that facilitated reaction between GA and oxygen. Minimum residual oxygen level decreased with GA content and temperature, from 4 to 50 °C. Rates of oxygen scavenging increased and residual oxygen decreased linearly with GA content. Compounding bio-based polymers with GA via in-situ extrusion efficiently produced active films which could be used to control oxygen in food packaging. • Novel oxygen absorbing bio-based polymer via extrusion compounding with gallic acid. • Gallic acid bonded starch and LLDPE, improving compatibility and plasticization. • Oxygen scavenging kinetics increased with temperature and gallic acid contents. • Minimum residual oxygen contents as low as 16% was reached by 5 days at 50 °C.