Edible Films Prepared with Different Biopolymers, Containing Polyphenols Extracted from Elderberry (Sambucus Nigra L.), to Protect Food Products and to Improve Food Functionality

Edible films and coatings can be used for packaging food, thus reducing the consumption of plastics in daily food products, and can also be enriched with active compounds to improve food functionality. The main goal of the current research was to produce edible films incorporating elderberry extract, an active ingredient rich in polyphenols that exhibits several therapeutic characteristics, to allow its protection and controlled release. To protect the active compound, different biopolymers were used (modified chitosan, sodium alginate and gum arabic) and films with different thicknesses were produced, by heat-induced gelation, using the conventional solvent casting method. Then, the formulations were evaluated to compare their properties in terms of entrapment efficiency, morphology, optical properties and release behaviour. The films exhibited entrapment efficiencies for polyphenols between 74.0 and 99.9%, presenting homogenous structures, which were predominantly transparent, flexible and yellowish, with a morphology that varied with the entrapment agent. The release of the polyphenols also depended on the entrapment agent used to protect them, with a faster release occurring for the films with gum arabic, followed by modified chitosan and, finally, by sodium alginate. The films’ thickness did not significantly affect the colour, morphology and release of the active agent. Using mathematical modelling, it was verified that, in general, the zero-order, the Korsmeyer-Peppas and the Weibull models are the kinetic equations producing a better adjustment to the experimental release profiles, with correlation coefficients that ranged from 0.981 to 0.996, 0.987 to 0.997 and 0.984 to 0.999, respectively. It can be concluded that films would be a good alternative to other systems for the delivery of active compounds, allowing the replacement of plastic materials for protecting food products.