Self-Assembled Pullulan-Silica Oxygen Barrier Hybrid Coatings for Food Packaging Applications

The scope of this study encompassed the evaluation of pullulan as a suitable biopolymer for the development of oxygen barder roetings to be applied on poly(ethylene terephthalate) (PET), especially for food packaging applications. To enhance the barrier properties of the organic phase (pullulan) even at high relative humidity values, an inorganic phase, tt.trough in situ polymerization, was also utilized to obtain hybrid coatings via the sol-gel technique. on microscopy (TEM) images and Fourier transform infrared (FT-IR) spectra showed that mixing the two phases yielded a there-dirnensional hybrid network formed by self-assembly and mediated by the occurrence of new hydrogenbcnti intcract at the intermolecular level, although the formation of new covalent bonds could not be excluded. The deposition of the hybrid coatings decreased the oxygen transmission rate (OTR) of the plastic substrate by up to 2 orders of. magnitude under tiry conditions. The best performance throughout the scanned humidity range (0%-80% relative humidity) was obtained for the formulation with the lowest amount of silica (that is, an organic/inorganic ratio equal to 3).