Diffusion of nisin in protein packaging films

The rate of release of biocides from packaging films can extend the shelf quality and safety of a variety of food products. Protein packaging films as nisin carriers were studied to characterize their ability to regulate nisin diffusion in aqueous model systems. The effects of protein film type (cast corn zein films (CCZ), heat-pressed corn zein films (HPCZ), cast wheat gluten films (CWG) and heat-pressed wheat gluten films (HPWG)) and exposure temperature (5, 25, 35 and 45°C) were investigated. Diffusivity was estimated in protein films immersed in aqueous media. The kinetics of nisin diffusion in the protein films followed a Fickian diffusion model. CCZ had the lowest nisin diffusivity, therefore the highest nisin retention. The diffusivities in HPCZ, CWG, and HPWG films were not significantly different. A decrease in temperature from 45°C to 5°C resulted in a reduction of diffusivity for all films studied. Temperature dependence of nisin diffusion in all films followed an Arrhenius model, which indicated no morphological changes occurred within 5–45°C. The activation energy for nisin diffusion in corn zein films was higher than that in wheat gluten films.