Whey protein-coated high oxygen barrier multilayer films using surface pretreated PET substrate

Abstract

Whey protein isolate (WPI)-coated multilayer films were developed using polyethylene terephthalate (PET) film as a substrate. To improve the interfacial compatibility between PET film and water-based WPI coating solution, various surface pretreatments (corona discharge, plasma, and primer coating) were applied to PET. Water contact angles of the plasma-treated PET were significantly decreased by 12.8% related to the untreated PET, suggesting an increment of hydrophilic functional groups. Oxygen transmission rates of surface-pretreated multilayer films with WPI coating layer [PET/WPI/nylon/linear low-density polyethylene (LLDPE)] were significantly lower, about 43-234 times, than the multilayer films without WPI film layer. In addition, tensile strength of the plasma-pretreated PET/WPI/nylon/LLDPE films was 13.4 and 21.8% higher, elongation at break was 29.7 and 2.6% higher than the corona discharge- and primer-pretreated films, respectively. Taken together, WPI films are promising candidates for replacing synthetic oxygen-barrier materials. Specifically, plasma-pretreated PET/WPI/nylon/LLDPE films have a high potential as high oxygen-barrier packaging materials. (C) 2018 Elsevier Ltd. All rights reserved.