Alginate/maltodextrin and alginate/shellac gum core-shell capsules for the encapsulation of peppermint essential oil

Encapsulation of essential oils represents a good strategy to protect and to transform them in free-flowing particles. Core-shell systems containing peppermint essential oil have been obtained by inverse ionotropic gelation. An O/W emulsion composed of essential oil (O) and aqueous CaCl2 solution enriched with hydroxyethylcellulose (W) was dripped in an alginate solution added of a secondary excipient (maltodextrin or shellac gum) at two concentrations. The qualitative/quantitative modifications of capsule shell composition had a limited impact on the essential oil content (it was more than 50% w/w), while they affected other dried capsule properties like dimensions, shell thickness, hardness and swelling behavior. Neither the type nor the amount of secondary excipient influenced wet capsule particle size (about 4 mm). After drying, particle size decreased (it was about 2 mm) and while shellac gum amount did not affect dried capsule dimensions, an increase in maltodextrin amount corresponded to an increase in their diameters. Capsule hardness diminished by increasing the amount of secondary excipient in the formulations. In addition, the amount of maltodextrin included in the formulations affected the swelling behavior of the dried capsules in water and this leads considering maltodextrin a useful excipient to modulate swelling according to the needs of the different applications.