Citrus Peel Extracts for Industrial-Scale Production of Bio-Based Active Food Packaging

The thermal stability of four different commercial citrus peel extracts was tested and improved by an encapsulation process with beta-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 dm(2) 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.

Automated summary

The thermal stability of four different commercial citrus peel extracts was improved by encapsulating them with beta-cyclodextrins in a spray-dryer. The encapsulated extracts maintained good antioxidant capacity and showed antimicrobial activity against Staphylococcus aureus. The best-encapsulated citrus extract was incorporated into a PLA/PHB film, which exhibited suitable properties for food contact.