Antimicrobial polyamide-alginate casing incorporated with nisin and ε-polylysine nanoparticles combined with plant extract for inactivation of selected bacteria in nitrite-free frankfurter-type sausage

The effects of combining a polyamide-alginate casing incorporated with nisin (100 ppm and 200 ppm) and ε-polylysine (500 ppm and 1000 ppm) nanoparticles and a mixed plant extract as ingredient in sausage formulation (500 ppm; composed of olive leaves (OLE), green tea (GTE) and stinging nettle extracts (SNE) in equal rates) were studied to improve the shelf life and safety of frankfurter-type sausage. The film characteristics and microbiological properties of sausage samples were evaluated. Sausage samples were packaged in polyethylene bags (vacuum condition) and analysed during 45 days of storage at 4◦ C. Control sausages were also treated with 120 ppm sodium nitrite. Polyamide-alginate films containing 100 ppm nisin and 500 ε-PL nanoparticles had the highest ultimate tensile strength compared to other films. However, 100 ppm nisin and 500 ε-PL nanoparti-cles decreased water vapour permeability of films. The results also revealed that nisin nanoparti-cles had significantly (p < 0.05) low inhibitory effects against Escherichia coli, Staphylococcus aureus, molds and yeasts and total viable counts compared to control and ε-PL nanoparticles. Furthermore, 1000 ppm ε-PL nanoparticles displayed the highest antimicrobial activity. Based on the obtained results, the films containing ε-PL nanoparticle could be considered as a promising packaging for frankfurter-type sausages.