title: "Wetting enhancer" pullulan coating for antifog packaging applications.
abstract: A new antifog coating 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 simulating the typical storage conditions of fresh foods. In these tests, the antifog efficiency of the pullulan coating 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 coating behaved as a "wetting enhancer", mainly due to the low water contact angle (∼24°), 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 coating on refrigeration during testing. 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 coating on the plastic substrate compared to the patchy surfacing of the antifog additives in the commercial films is another important factor dictating the best performance of the antifog pullulan coating.
authors: DeFENS, Department of Food, Environmental and Nutritional Sciences, Packaging Division, University of Milan , Via Celoria 2, I - 20133 Milan, Italy.
authors: Laura
authors: L
authors: Introzzi
authors: José María
authors: JM
authors: Fuentes-Alventosa
authors: Carlo A
authors: CA
authors: Cozzolino
authors: Silvia
authors: S
authors: Trabattoni
authors: Silvia
authors: S
authors: Tavazzi
authors: Claudia L
authors: CL
authors: Bianchi
authors: Alberto
authors: A
authors: Schiraldi
authors: Luciano
authors: L
authors: Piergiovanni
authors: Stefano
authors: S
authors: Farris
mesh_terms: D001704:Biopolymers / Q000737:chemistry / Q000494:pharmacology; D020099:Coated Materials, Biocompatible / Q000138:chemical synthesis* / Q000737:chemistry; D018857:Food Packaging / Q000295:instrumentation / Q000379:methods; D005936:Glucans / Q000737:chemistry* / Q000494:pharmacology*; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D018625:Microscopy, Atomic Force; D056951:Photoelectron Spectroscopy; D010969:Plastics; D013227:Steam; D013499:Surface Properties; D017155:Wettability / Q000187:drug effects*
chemical_list: D001704:Biopolymers; D020099:Coated Materials, Biocompatible; D005936:Glucans; D010969:Plastics; D013227:Steam; C009109:pullulan