Degradation behavior of multilayer packaging films in the presence of a highly acidic sauce

Abstract

Highly acidic condiments such as hot sauce can deteriorate multilayer packaging films. To date, only a multilayer polymeric film (polyethylene terephthalate/ink/polyethylene/foil/polyethylene/SiO x coated polyethylene terephthalate/adhesives/Barex®) utilizing a proprietary resin, Barex® as one of its polymeric layers can preserve hot sauce for military rations. However, the production of Barex® stopped in 2016. To identify substitutes for Barex®, an immersion study of films in hot sauce was conducted with several commercially available multilayer films (Polyethylene terephthalate/ink/adhesive/polyamide/adhesive/polypropylene and polyethylene terephthalate/waste low-density polyethylene/aluminum foil/adhesive/polyester/low-density polyethylene) and a monolayer Barex® (acrylonitrile methyl acrylate copolymer) film. All films were immersed in hot sauce, acetic acid, and sodium chloride solutions at 50 °C for 12 weeks. The mass, thickness, morphology, and chemical compositions of each film were analyzed every three weeks. Hot sauce and acetic acid solution similarly deteriorated multilayer films, causing delamination and oxidative degradation, but not sodium chloride solutions. This indicates that the failure of the multilayer packaging of hot sauce was likely caused by the low pH environment, not heat or salt ions. The two primary innovations in this study are: 1) the finding that acidic components in hot sauce deteriorate multilayer packaging by transforming aluminum foil into a soluble salt and by oxidizing polyethylene, and 2) surface erosion plays a significant role in inducing polyethylene oxidation. This is the first study to describe how a highly acidic food deteriorates multilayer packaging used for military rations. Possible deterioration mechanism of the multilayered structure (Film 2) in presence of a highly acidic hot sauce. • Acetic acid in hot sauce reacts with aluminum foil used in multilayer films. • Acids in hot sauce oxidatively degrade polyethylene (PE) layers in multilayer films. • PE in multilayer films oxidizes more in hot sauce than in acetic acid solutions. • PE in multilayer films surface erodes when immersed in hot sauce and acetic acid. • Potential multilayer film is identified for replacing Barex® for military rations.