Identifying Performance Conditions for a Radical Scavenging Active Packaging Material

Abstract

ABSTRACTGlobal food waste remains a significant economic and environmental burden throughout the food supply chain. Oxidative degradation and microbial growth are two of the most prominent causes of post‐manufacturing food spoilage and are thus often targets of active packaging technologies that seek to maintain or improve shelf life by adding preservative functionality to the packaging material. In non‐migratory active packaging, the active agent is bound to the polymer backbone preventing its migration to the foodstuff in support of consumer demands for cleaner labels. Critical to commercial translation of such non‐migratory active packaging technologies is identifying circumstances conducive to their optimal performance as well as those for which performance falls short of predicted behaviour. Here, we present an applications study to identify conditions of optimal performance of a non‐migratory radical scavenging active packaging material, polypropylene‐graft‐polyethyleneimine (PP‐g‐PEI5), synthesized by reactive extrusion of polyethylenimine with maleic anhydride functionalized polypropylene. Polyethylenimine was selected as an active agent for its reported radical scavenging and antimicrobial behaviour. Despite introduction of a hygroscopic and relatively low molecular weight active ligand, PP‐g‐PEI5 retained desirable low water vapour transmission rates (value) and excellent mechanical properties, supporting its covalent bonding to the base polymer. Interfacial pKa was determined via a pH‐dependent characterization of surface primary amine to be 10.07 (9.66–11.42, 95% CI), explaining its antioxidant mechanism at food and beverage relevant pH values (under 7) due to radical scavenging and not transition metal sequestering behaviour. Antimicrobial efficacy was demonstrated against gram‐positive Listeria monocytogenes. Finally, a viscosity‐dependent radical scavenging assay demonstrated the efficacy of PP‐g‐PEI5 as an antioxidant active packaging material in food products up to 812.9 cPs (2.98 nmol/cm2 Troloxeq). These results suggest that these active packaging materials would be most effective in inhibiting radical induced oxidative degradation in foods and beverages of acidic to neutral pH values and viscosities from liquid to loose gel, for example, preventing lipid oxidation in salad dressings or enhancing stability of natural colours in juices or smoothies. The reported active packaging material offers industry and consumers another tool for extending the shelf life of foods while addressing clean label market demands, which may help to decrease food waste by reducing losses post‐retail due to oxidative degradation and microbial growth.