Development of gelatin-coated ι-carrageenan hydrogel capsules by electric field-aided extrusion. Impact of phenolic compounds on their performance

The aim of this work was to develop edible encapsulation structures based on gelatin-coated iota-carrageenan hydrogel beads, and to study the impact of incorporating different phenolic compounds within them in their microstructure, physic-chemical properties and release performance. The developed capsules were produced in aqueous solutions and mild conditions (i.e. suitable for food applications and sensitive bioactive compounds) by electric field-aided extrusion of iota-carrageenan solutions onto a gelatin bath containing calcium chloride, and exhibited shape-memory behaviour upon re-hydration in water after freeze-drying. The impact of loading them with gallic acid, catechin, chlorogenic acid and tannic acid was evaluated, and the results showed that only tannic acid could be efficiently incorporated within the hydrogel structures, while it limited the binding of the gelatin coating and altered the structure and thermal properties of the capsules. Reducing the concentration of tannic acid minimised its impact on the structure of the beads without negatively affecting its release, which was found to be however affected by the capsule size. The potential of these structures for the encapsulation of hydrophobic compounds was also anticipated.