Plant proteins at low concentrations as natural emulsifiers for an effective orange essential oil microencapsulation by spray drying

Abstract

In this work, pea and soy proteins were used as emulsifiers on the encapsulation of orange essential oil (OEO, rich in d-limonene) by emulsification followed by spray drying. A commercial pea protein concentrate (PPC) was studied regarding its ability to act as an emulsifier, stabilize oil-in-water emulsions containing OEO, and to produce spray-dried microparticles in comparison to a commercial soy protein isolate (SPI), which is an emulsifier that has been already used on the microencapsulation of flavors. Both PPC and SPI presented low solubility in water at their natural pH; however, the even lower solubility of PPC resulted in lower adsorption at the oil-water interface. High solids oil-in-water emulsions stabilized using different concentrations of PPC or SPI (0.6–6.0 wt%) presented different physicochemical properties and physical stability due to the difference between the solubility of PPC and SPI in water. The spray-dried microparticles produced from selected SPI emulsions presented better stability during the drying stage than PPC emulsions, which resulted in higher OEO retention values (84.1–100 wt% and 92.6–97.9 wt% for PPC and SPI, respectively). Overall, the spray-dried microparticles produced using PPC or SPI present similar physical properties that promote the protection of the encapsulated OEO. Based on these results, despite its low solubility, pea protein can be used for encapsulating OEO effectively; therefore, its use as an emulsifier on the encapsulation of other different flavor compounds must be explored even further.