Physicochemical Characterization of Packaging Foils Coated by Chitosan and Polyphenols Colloidal Formulations

Abstract

In this research, antimicrobial polysaccharide chitosan was used as a surface coating for packaging material. The aim of our research was to establish an additive formulation of chitosan and antioxidative plant extracts as dispersion of nanoparticles. Chitosan nanoparticles with embedded thyme, rosemary and cinnamon extracts were synthesized, and characterized for this purpose. Two representative, commercially used foils, polypropylene (PP) and polyethylene (PE), previously activated by UV/ozone to improve coating adhesion, were functionalized using chitosan-extracts nanoparticle dispersions. The foils were coated by two layers. A solution of macromolecular chitosan was applied onto foils as a first layer, followed by the deposition of various extracts embedded into chitosan nanoparticles that were attached as an upper layer. Since active packaging must assure bioactive efficiency at the interface with food, it is extremely important to understand the surface characteristics and phenomena of functionalized foils. The physico-chemical analyses of functionalized foils were thus comprised of surface elemental composition, surface charge, wettability, as well as surface morphology. It has been shown that coatings were applied successfully with an elemental composition, surface charge and morphology that should enable coating stability, homogeneity and consequently provide an active concept of the packaging surface in contact with food. Moreover, the wettability of foils was improved in order to minimize the anti-fogging behavior.

Bioactive Characterization of Packaging Foils Coated by Chitosan and Polyphenol Colloidal Formulations

“…Furthermore, chitosan itself shows very poor antioxidant behavior and, thus, it has no significant effect on the phenolic content. The highest total phenolic content was observed for chitosan nanoparticles with embedded cinnamon extract (CSNPs CIN), which correlates with the result for pure cinnamon, as the richest in phenolic substances [23]. Table 2 reports oxygen transmission rates for untreated reference PE and PP foil and functionalized foils, which is an extremely important property to control food spoilage.…”

“…The final amount of the extract, which was encapsulated into chitosan nanoparticles and further applied onto the foil surface, was 4× its MIC, in order to obtain good antimicrobial activity of functionalized foils. The total phenolic contents of thyme, rosemary, and cinnamon, as well as of chitosan nanoparticles with embedded extracts, were already reported and discussed in our previous paper [23]. It was shown that the concentration of phenols in extract solutions was the highest in cinnamon, followed by rosemary and then thyme.…”

“…To alleviate these problems, smaller amounts of essential oils can be combined with other antimicrobial compounds. One of the intelligent approaches could be the combination of extracts with polysaccharides as a coating for films [19][20][21][22][23][24] in order to positively change their mechanical, optical or barrier properties and to introduce bioactive properties in a suitable way. The use of antioxidants in synergistic formulation with other biopolymers as nanoparticles, with enlarged contact area compared to conventional antioxidant agents, might allow for a reduction in the amount of active substances, which would act very efficiently while simultaneously reducing and/or avoiding the effect of active substances on the required properties of the base packaging material [25][26][27].…”

“…In our previous work, the first part of this complex study, we reported the smart approach for the development of active packaging for two representative, commercially used foils, polypropylene (PP) and polyethylene (PE), previously activated by ultraviolet (UV)/ozone, using chitosan-extract colloidal dispersions as a coating for foils [23]. A solution of macromolecular chitosan was applied as a first layer onto PE and PP foils, followed by the deposition of various extracts (rosemary, thyme, and cinnamon) encapsulated into chitosan nanoparticles as an upper, second layer.…”

“…Higher stability and homogeneity of the coating were obtained in this way. It was shown [23] that analyzed physico-chemical parameters such as surface charge, elemental composition, hydrophilicity/hydrophobicity, and morphology were promising for providing good bioactive properties. The latter hypothesis was verified in this paper.…”