Supercritical impregnation of food packaging films to provide antioxidant properties

Among the different techniques employed to develop active packaging, supercritical solvent impregnation (SSI) of natural extracts is an innovative approach. When developing a method to obtain polyethylene terephthalate/ polypropylene (PET/PP) films with antioxidant capacity, several parameters (pressure, temperature, depressurization rate, presence of modifier and time) were studied with caffeic acid as a model substance. The best conditions were applied to an olive leaf extract as a natural extract with antioxidant properties. Antioxidant activity was evaluated by the DPPH assay and the total loading was calculated to identify the best impregnation conditions. The results revealed that a low level of impregnation provide antioxidant films, both with the standard and the natural extract. Better results were obtained when the natural extract was used. To confirm the presence of the antioxidant particles and to determine their distribution on the matrix, the impregnated samples were studied by Scanning Electron Microscopy (SEM).