Abstract
The main function of food packaging is to maintain food’s quality and safety. The use of active packaging, including antimicrobial materials, can significantly extend the shelf life of food. Many of these packaging solutions are based on the application of polymer films containing metal nanoparticles (e.g., Ag, Au, Cu) or metal oxides (e.g., TiO2, ZnO, MgO). However, the use of iron nanoparticles is rarely mentioned. In the study, polylactide (PLA) films containing zero-valent iron (ZVI) were made by casting method. Pure PLA films and PLA films with the addition of Fe2O3 were used as comparative materials. The composition and structure of ZVI/PLA films were evaluated with scanning electron microscopy. The XRD spectra performed on ZVI/PLA films confirmed the presence of iron in the packaging material and revealed their oxide form (Fe2O3). The addition of zero-valent iron in the concentration 1%, 3%, or 5% resulted in the formation of crystallographic planes measuring 40.8, 33.6, and 28.6 nm, respectively. The color and gloss of the films, and their antimicrobial activity against bacteria (Bacillus subtilis, Escherichia coli, Staphylococcus epidermidis) and fungi (Geotrichum candidum, Rhodotorula rubra) were also examined. The PLA films with addition of 3% of ZVI (w/w) inhibited the growth of all tested organisms in contrast to PLA and PLA/Fe2O3 films. The addition of ZVI to polymer matrix caused changes in its appearance and optical properties. The ZVI/PLA coating used on polyolefin film allowed to extend the shelf life of goat cheese packed in examined material to 6 weeks. Considering the antimicrobial properties of the ZVI/PLA films and PLA biodegradability the obtained material can be successfully applied in the food industry.
Highlights
The basic functions of food packaging are closely linked to their role in ensuring food quality and safety in the supply chain and during the storage of groceries by consumers [1]
(w/w) addition of zero-valent iron are relatively uniformly distributed (Figure 1a), whereas the increase in ZVI concentration to 3% (w/w) led to higher density and uniformity in Fe nanoparticles distribution nanoparticles distribution (Figure 1b)
Active packaging with antimicrobial properties actively affects the growth of microorganisms inside and/or on the surface of the packed food, and their effectiveness depends on the mechanism of action of the active agent and the way it is introduced into the packaging material
Summary
The basic functions of food packaging are closely linked to their role in ensuring food quality and safety in the supply chain and during the storage of groceries by consumers [1]. Used conventional forms of packaging ensure, above all, the protection of packed products, provide information about them and enable their convenient consumption [2,3]. Active packaging and materials actively contribute to reducing the effects of the above-mentioned adverse factors and increase the functionality of conventional packaging systems most often by releasing the desired or absorbing harmful substances from the packed product and/or its environment [4,5]. The use of active packaging solutions can significantly extend the shelf life of food and reduce the costs associated with protecting food against spoilage as well as disposal of already wasted products. Active packaging is useful for perishable food products such as Coatings 2020, 10, 156; doi:10.3390/coatings10020156 www.mdpi.com/journal/coatings
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