Encapsulation of Zanthoxylum schinifolium essential oil by complex coacervation with whey protein isolate and gum Arabic for improved stability and controlled release

Zanthoxylum schinifolium essential oil (ZSEO) exhibits remarkable antioxidant and antibacterial biological activities and is widely used in the food industry. However, its low water solubility, high volatility, and susceptibility to decomposition by light, heat, and oxygen complicate its transport and storage. Microencapsulation of ZSEO is an effective method that can overcome these limitations and expand its application scope. To enhance stability and preserve functionality of ZSEO, ZSEO-loaded microcapsules were produced by complex coacervation of whey protein isolate (WPI) and gum Arabic (GA), followed with freeze-drying. So far, no comprehensive research has been conducted on the method of microencapsulating ZSEO using WPI/GA. Through research, the optimal pH for the formation of WPI/GA (1:1, w/w) complex coacervates was found to be 3.9. The ZSEO-in-water (O/W) emulsions stabilized by whey protein isolate (WPI) were prepared, which exhibited a uniform size of around 200 nm and showed enhanced stability with increasing WPI contents (3.0–6.0 wt%). After complex coacervation with GA, the resulting microcapsules showed improved physical properties and higher encapsulation efficiency as the ratio of WPI/GA complex wall material increased. The ZSEO-loaded microcapsules still maintained their ability to scavenge 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2’-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) free radicals compared to free ZSEO, especially performing the optimal antioxidant activity at a core-to-wall ratio of 5:8 (w/w). Release kinetics studies confirmed controlled and delayed release of ZSEO from the microcapsules in various food simulants (aqueous, ethanolic and aerial environments). This work demonstrated that microencapsulation via WPI/GA complex coacervation was an effective strategy to encapsulate essential oils with high antioxidant activity and controlled release.