Microencapsulation of pink pepper essential oil: Properties of spray-dried pectin/SPI double-layer versus SPI single-layer stabilized emulsions

Abstract

Microencapsulation by spray drying of hydrophobic materials, such as pink pepper essential oil (Schinus terebinthifolia Raddi), relies on the efficient stabilization of the oil-in-water emulsion to be dried. Association colloids resulting from electrostatic interactions between proteins and polysaccharides are able to provide higher interfacial activity when compared to proteins alone. The main purpose of this work was to examine the role of pectin in the physicochemical properties of powders produced by spray-drying emulsions stabilized by protein single-layer or by protein/pectin double-layer. Oil retention, water activity, hygroscopicity, reconstitution, flow behavior, particle size and morphological properties were evaluated. Powders produced from double-layer emulsions had higher oil retention and, despite presenting higher water activity, were less hygroscopic (0.280, 8.5%) when compared to single-layer powders (0.176, 9.3%). Double-layer powders also showed higher contact angle and higher wetting time in water. Both powders had good water solubility (about 70%) and good dissolution in water and in oil. Powder flowability was affected by formulation, with single-layer powders presenting greater cohesion than double-layer ones. Addition of pectin allowed a more homogeneous distribution of particle sizes, preventing formation of oversized particles and agglomerates. Scanning electron microscopy showed spherical particles with absence of pores, which is desirable for greater preservation of the volatile compounds. Based on the complete set of results, double-layer powders presented higher oil retention and better shelf life properties than single-layers ones, showing the ability of association colloids between soy proteins and pectin to enhance the possibilities of applying pink pepper essential oil in the food industry.