Abstract
The thermal stability of four different commercial citrus peel extracts was tested and improved by an encapsulation process with β-cyclodextrins in a spray-dryer. All extracts after the encapsulation process maintained a good antioxidant capacity, with an apparent loss in total phenolic compounds of around 20–25%. In addition, all samples showed good antimicrobial activity (MIC 5–0.625 mg/mL) against Staphylococcus aureus, which was maintained after the encapsulation process (MIC 5–1.25 mg/mL). Based on the antioxidant and antimicrobial activity results, the best-encapsulated citrus extract was selected for incorporation into a polylactic acid/polyhydroxy butyrate (PLA/PHB) film. The latter was then produced on an industrial scale by cast extrusion and was found to be suitable for food contact as it showed overall migration values in different food simulants lower than the legislative limit of 10 mg of non-volatile substances per 1 dm2 of surface area. The UHPLC-HRMS analysis, performed to evaluate the migration of the active compounds, revealed about 13.41% release in food simulant A and 11.02% in food simulant B. Antimicrobial analysis conducted directly on the film showed a growth inhibition activity towards Escherichia coli and Staphylococcus aureus equal to 30 and 60%, respectively.
Highlights
Nowadays, the reduction of the potential risks associated with the use of synthetic compounds in food products and the limitations in using chemical additives are two hot-topics of research [1]
The latter is strictly dependent on the type of plant matrix, the extraction method, and the incorporation processes into the polymer [9,10]
The yields (%) of the spray-drying encapsulation process resulted in more than 100%
Summary
The reduction of the potential risks associated with the use of synthetic compounds in food products and the limitations in using chemical additives are two hot-topics of research [1]. Active packaging systems are designed to promote interactions between the packaging itself, the food, and the internal environment In this framework, natural extracts represent a valuable source of bioactive compounds, such as polyphenols, characterized by well documented in vitro and in vivo antioxidant and antimicrobial properties [3,4] and they can be incorporated in or coated on food packaging materials to prevent microbial development, reduce lipid oxidation, and thereby extend the shelf-life of packaged foods [4,5,6]. Natural extracts can be obtained from different natural sources, such as fruits (e.g., grape and pomegranate), herbs and spices (e.g., tea, rosemary, oregano, and cinnamon), or, in a more sustainable view, from plant by-products, such as grapefruit seeds, grape pomace, orange peels, green tea and olive leaves, which are valued for their high functionality and/or bioactivity [1,7,8]. The latter is strictly dependent on the type of plant matrix, the extraction method, and the incorporation processes into the polymer [9,10]
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