Reactive Extrusion of Nonmigratory Active and Intelligent Packaging

The environmental and economic burden of food waste demandsnewpreservation technologies to reduce the degradative actions of spoilagesuch as moisture, oxygen, and microorganisms. Direct food additivescan help maintain product quality; however, the limited life spanof these additives combined with consumer desire for "cleanlabel" products has motivated research into new food manufacturingtechnologies like active and intelligent packaging that can preventand detect food spoilage. In this work, curcumin was grafted to polypropylene(PP-g-Cur) via reactive extrusion to produce nonmigratoryactive and intelligent packaging through a solvent-free, efficient,and continuous method. Immobilization of curcumin was confirmed bya standard migration assay exhibiting a maximum of 0.011 mg/cm(2) migration, significantly below the EU migratory limit forfood contact materials (0.1 mg/cm(2)). Compared to nativePP films, PP-g-Cur films blocked 93% of UV lightwhile retaining 64% transparency in the visible region, allowing fordesirable product visibility while inhibiting UV degradation of packagedgoods. While the ability of PP-g-Cur to inhibit growthof E. coli and L. monocytogenes was insignificant compared to controlPP, free curcumin exhibited poor bacterial inhibition as well, suggestingthat without hydrophilic modification, native curcumin has limitedantimicrobial efficacy. PP-g-Cur films displayedsignificant radical scavenging in both organic (11.71 +/- 3.02Trolox(Eq) (nmol/cm(2))) and aqueous (3.18 +/- 1.04 Trolox(Eq) (nmol/cm(2))) matrices, exhibitingpotential for antioxidant behavior in both lipophilic and hydrophilicapplications. Finally, when PP-g-Cur films were exposedto ammonia, an indicator of microbial growth, the color visually andquantitatively changed from yellow to red, demonstrating potentialto indicate spoilage. These findings demonstrate the potential ofa scalable technology to produce active and intelligent packagingto limit food waste and advance the capabilities of functional materialsin a variety of applications.