title: Chitosan coating improves retention and redispersibility of freeze-dried flavor oil emulsions.
abstract: Flavor oils are often encapsulated as emulsions by drying processes such as freeze-drying or spray-drying, using mainly macromolecular emulsifiers such as gums and proteins to stabilize the emulsions during drying. The objective of the present study was to examine whether a combination of a charged small-molecule emulsifier and an oppositely charged polysaccharide adsorbed to the emulsion droplet surface can substitute commonly used encapsulation materials for the drying of flavor oil emulsions. To this end, polysaccharide-coated flavor oil emulsions were prepared by high-pressure homogenization of mixtures consisting of a flavor oil (R-carvone), a negatively charged citric acid ester small-molecule emulsifier (citrem), and various concentrations of a positively charged polysaccharide (chitosan) in acetate buffer at pH 4.0. Nanoemulsions with average particle diameters of approximately 100 nm in the absence and approximately 230-250 nm in the presence of chitosan coating were obtained. These emulsions were subsequently freeze-dried with different concentrations of maltodextrin, which served as the main encapsulation material. It was demonstrated that coating the oil droplet surface with a small amount of chitosan resulted in remarkably improved retention levels and redispersibility properties of the freeze-dried carvone emulsions. Maltodextrin content also affected both retention and redispersibility. At optimal chitosan and maltodextrin concentrations approximately 95% retention levels were obtained, and the average particle sizes of freeze-dried and redispersed emulsions were approximately 270-300 nm, as compared to approximately 230-250 nm before freeze-drying. The results demonstrate that charged small-molecule emulsifiers used in combination with oppositely charged polymers are viable alternatives to macromolecular emulsifiers for freeze-drying of flavor oil emulsions.
authors.affiliation: Danish Technological Institute, Holbergsvej 10, DK-6000 Kolding, Denmark. thomas.kaasgaard@teknologisk.dk
authors.forename: Thomas
authors.initials: T
authors.lastname: Kaasgaard
authors.forename: Danielle
authors.initials: D
authors.lastname: Keller
mesh_terms: D000972:Antineoplastic Agents, Phytogenic / Q000737:chemistry; D002214:Capsules; D048271:Chitosan / Q000737:chemistry*; D000081005:Cyclohexane Monoterpenes; D004655:Emulsions / Q000737:chemistry*; D005612:Freeze Drying / Q000379:methods; D008027:Light; D039821:Monoterpenes / Q000737:chemistry; D009821:Oils / Q000737:chemistry*; D011134:Polysaccharides / Q000737:chemistry; D012542:Scattering, Radiation
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D002214:Capsules; D000081005:Cyclohexane Monoterpenes; D004655:Emulsions; D039821:Monoterpenes; D009821:Oils; D011134:Polysaccharides; C006923:carvone; C008315:maltodextrin; D048271:Chitosan