A new antifog coa
ting made of pullulan is described in this work. The antifog properties are discussed in terms of wettability, surface chemistry/morphology, and by quantitative assessment of the optical properties (haze and transparency) before and after fog formation. The work also presents the results of antifog tests simula
ting the typical storage conditions of fresh foods. In these tests, the antifog efficiency of the pullulan coa
ting was compared with that of two commercial antifog films, whereas an untreated low-density polyethylene (LDPE) film was used as a reference. The obtained results revealed that the pullulan coa
ting behaved as a 鈥渨et
ting enhancer鈥? mainly due to the low water contact angle (24掳), which in turn can be ascribed to the inherent hydrophilic nature of this polysaccharide, as also suggested by the X-ray photoelectron spectroscopy experiments. Unlike the case of untreated LDPE and commercial antifog samples, no discrete water formations (i.e., droplets or stains) were observed on the antifog pullulan coa
ting on refrigeration during tes
ting. Rather, an invisible, continuous and thin layer of water occurred on the biopolymer surface, which was the reason for the unaltered haze and increased transparency, with the layer of water possibly behaving as an antireflection layer. As confirmed by atomic force microscopy analysis, the even deposition of the coa
ting on the plastic substrate compared to the patchy surfacing of the antifog additives in the commercial films is another important factor dicta
ting the best performance of the antifog pullulan coa
ting.
Keywords:
antifog; ting&qsSearchArea=searchText">coating; packaging; pullulan; surface; ting&qsSearchArea=searchText">wetting