Encapsulation of essential oils using hemp protein isolate–gum Arabic complex coacervates and evaluation of the capsules

Abstract

Complex coacervates between hemp protein isolate and gum Arabic were prepared and used as an emulsifier and encapsulant for four different essential oils (oregano, mustard, grapefruit and lemon). The properties of the capsules including encapsulation efficiency, ability to disperse in the aqueous phase, thermal stability, microstructure, release pattern, and antioxidative and antibacterial properties were determined and found to be affected by the type or nature of the essential oil used. The capsules of oregano essential oil showed the highest encapsulation efficiency, ability to disperse in the aqueous phase, most compact structure, highest thermal stability, antioxidant activity and the slowest release rate. Capsules of each essential oil had better antibacterial activity than their corresponding free/unencapsulated state, except for oregano essential oil in which the free essential oil exhibited higher antibacterial activity than the corresponding capsules. The release of essential oil from each capsule was fitted well using the Weibull model and showed a complex release mechanism including matrix erosion. This study contributes to the science and technology to deliver essential oil microcapsules through a benign (complex coacervation) pathway and contributes sustainability by offering an alternative pathway to utilize hemp protein (which is still a by-product of the hemp oil industry).