(720j) Degradation Behavior of Flexible Packaging Films in Acidic Environments

Highly acidic condiments such as hot sauce show a negative effect on packaging films, shortening the packaged food’s shelf life. This study investigates the degradation behavior of several multilayered packaging films when exposed to hot sauce. In this study, four multilayered and two monolayered flexible packaging films were examined where the distinct monolayered films and the individual layers of the multilayered films are mainly of acrylonitrile copolymer, polypropylene, polyester, polyethylene, and nylon. An accelerated immersion test was carried out at 50°C for 12 weeks to simulate a 3-year storage time. The films were characterized in terms of their weight, thickness, morphology (surface and cross-section), and oxygen barrier properties before and after exposure to the hot sauce. The chemical compositions, thermal transitions, and enthalpy of the films were also evaluated using Fourier-transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). Delamination in three multilayered structures was observed. Thermal oxidation and/or hydrolysis were found in the delaminated layers. After exposure to the hot sauce, new signals corresponding to hydroxyl and carbonyl groups were observed in FTIR. The immersion test in the highly acidic hot sauce also reduced the melting enthalpies of polymers in the delaminated flexible packaging films and the glass transition temperature in some cases. In contrast, the non-delaminated films display comparable melting enthalpy. Based on the results from this study, flexible packaging films containing acrylonitrile copolymer, polypropylene, or nylon in multilayered structures are recommended for highly acidic condiment storage.