Microencapsulation of olive leaf extract by freeze-drying: Effect of carrier composition on process efficiency and technological properties of the powders

In this study the effect of matrix composition on process encapsulation efficiency, antioxidant capacity and physical properties of microencapsulated olive (Oleo europaea L.) leaves extract (OLE) powders obtained by freeze-drying were investigated. Total solids, matrix composition (maltodextrin and trehalose, alone or mixtures) and OLE:matrix ratio of the initial aqueous system were investigated by applying a Response Surface Methodology. Results highlighted that encapsulation efficiency resulted positively affected by higher concentrations of maltodextrin and lower OLE:matrix ratio. Thermal properties were influenced by the overall composition of the powders with an increased T-g at increasing maltodextrin content while OLE had a plasticizing effect. By microscopy analysis, differences in surface and particle morphology as well as OLE distribution in the differently formulated powders were observed in agreement with the corresponding encapsulation efficiency. This study highlights the importance of formulation optimization in freeze-drying encapsulation to enhance process efficiency and the technological functionalities of the powders.