Abstract
Chitosan films with olive leaf extract (OLE) incorporated at different concentrations were characterized regarding their antimicrobial, antioxidant and some relevant physical properties (i.e., solubility, water vapor permeability, and tensile properties). Results indicate that the active films have substantial antimicrobial activity against Listeria monocytogenes and Campylobacter jejuni mostly extending the microorganisms lag phase. A lower level of inhibition was found in the case of Escherichia coli. However, the OLE seems not to improve the intrinsic antimicrobial properties of the chitosan itself, except for C. jejuni. These results were confirmed with in situ testing using chicken. The chitosan films with OLE exhibited antioxidant activity, increasing with the OLE concentration, from 0.04 to 0.15 g/L ascorbic acid equivalents, corresponding to films with 10%–30% OLE relative to the chitosan. Chitosan films loaded with OLE exhibited a higher solubility in food simulants and a reduced permeability against water vapor. Overall, the combination of OLE and chitosan allows to obtain a promising active bio-based packaging solution for addressing safety and quality issues.
Highlights
Food loss and food waste, besides representing an economic and a societal issue, are a major problem today because of the high impact that they might have on the environment [1]
The CH tested showed an average deacetylation degree (DD) of 87.18% ± 3.44 %, which is accordance with what is reported by the supplier, if differences between methods of determination are taken into consideration [30]
The effect of DD was found to be more significant against Gram-negative bacteria (E. coli and C. jejuni) than against Gram-positive (L. monocytogenes) which is related to electrostatic mechanisms involving the interaction between negative bacterial cell wall and positively charged chitosan due to protonation of the -NH2 groups [32]
Summary
Food loss and food waste, besides representing an economic and a societal issue, are a major problem today because of the high impact that they might have on the environment [1]. According to the EU legislation [7], active packaging can be defined as a packaging system that is able to interact with the food and with the environment surrounding the food by absorbing or releasing substances from or into the food These mechanisms aim to enhance the safety or sensory properties of the food product, while maintaining its quality and extending its shelf life [8]. Olive leaf extract (OLE) is one of the highest value by-products arising from the olive oil industry It is a dark-brown liquid with a bitter taste and a high percentage of active compounds belonging to secoiridoids, hydroxytyrosol, polyphenols, triterpenes, and flavonoids in different concentrations depending on both cultivar and environmental conditions [24]. Coatings 2021, 11, 1339 chicken breast, demonstrating the validity of this approach for the development of active biopolymer films as an alternative to conventional plastics for shelf-life extension purposes
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