CONSEQUENCES OF POLYPROPYLENE FILM IONIZATION ON THE FOOD-PACKAGING INTERACTIONS

The influence of ionising treatment on plastic packaging is dealt with in the context of food safety. Various samples of polypropylene (PP) were investigated by Electron Spin Resonance (ESR) following irradiati on with an accelerated electron beam. In the presence of air, alkyl ra dicals (P-.) formed by ionisation under vacuum are quickly oxidised in to peroxyl radicals (POO.), whose stability varies with their location . Reaction derivatives of the aminoxyl type (>NO.) have been detected after ionisation of films doped with amine light stabilisers (of the H ALS or hydroxyphenylbenzotriazole type). Control and irradiated sample s of PP were then immersed in liquid food simulating fatty acid esters . After contact with films doped with light stabilisers, >NO. derivati ves were detected in the contact media. Two types of contamination wer e demonstrated: either by reaction of the stabiliser in the packaging before migration, or by migration followed by reaction with hydroperox ides present in the contact medium.