Extruded polymer films for optimal enzyme-catalyzed oxygen scavenging

• The enzymes in the dry coating can be activated through water-vapor transmission through an extruded plastic layer.
• A high water-vapor transmission is crucial for the oxygen-scavenging activity.
• Migration of components of the active coating is eliminated by addition of a plastic.
• Extrusion coating with PLA resulted in the highest oxygen-scavenging capacity.

The use of enzymes as oxygen scavengers has a great potential in the food packaging industry. Enzymes can be incorporated into a coating layer that can be applied directly onto the packaging material. For the system to be fully functional, there is however a need for the packaging to have some barrier properties, to be sealable through heat, and to ensure low or no migration of the active coating to the food. Various combinations of polypropylene (PP), poly(lactic acid) (PLA) and low density polyethylene (LDPE) were extruded onto board coated with the oxygen-scavenging enzyme. Properties such as oxygen-transmission rate, water-vapor transmission rate, heat-sealability, migration and oxygen scavenging capacity were evaluated. All combinations of extruded material resulted in a packaging material able to scavenge the oxygen at both 84% and 100% relative humidity. The greatest decrease in oxygen concentration of the head space of air-tight chambers was achieved with the material extruded with PLA on at least one side. It was found that the extruded plastic is necessary in order to meet the EU directives on migration from food packaging materials of not more than a total of 10 mg/dm2 material. All plastics were heat sealable against themselves but not against any of the other plastics and only LDPE adhered strongly to the enzyme-containing coating.