Extruded phosphorescence based oxygen sensors for large-scale packaging applications

Extruded phosphorescent O-2-sensitive composite materials comprising cross-linked polystyrene-divinylbenzene (PS-DVB) microspheres impregnated with Pt-benzoporphyrin dye and dispersed in low-density polyethylene (LDPE) or polylactic acid (PLA) carrier polymer are described. The sensors produced by hot melt extrusion method are specifically tailored to large-scale packaging applications and non-destructive measurement of residual O-2 in packaged food products. A panel of LDPE and PLA based sensor materials in the form of extruded pellets and thin film structures were produced and their structural features and O-2 sensing characteristics assessed with the view of packaging applications. The extruded LDPE film sensors were also integrated in packaging materials by heat lamination, to produce 'smart' packaging materials which also protect the sensor from direct contact with food. Analytical performance of extruded sensors was demonstrated by incorporating them in modified atmosphere packaged meat and cheese samples and monitoring residual O-2 levels in these packs non-destructively with a handheld Optech (R) reader over product shelf life. The extruded O-2 sensors show superiority over the sensors previously used or usable in packaged food products. This technology advances scaled manufacturing of optical O-2 sensors, their integration in packaging platforms and cost reduction.