Microencapsulation of Sichuan pepper essential oil in soybean protein isolate-Sichuan pepper seed soluble dietary fiber complex coacervates

Sichuan pepper essential oil (SPEO) possesses pleasant aroma, unique flavor, and various bioactivities; however, it has high volatility, poor stability, and low water solubility. In order to overcome the disadvantages and increase its application in foods, microcapsules of SPEO were developed through complex coacervation followed by spray drying. Sichuan pepper seed soluble dietary fiber (SDF) and soybean protein isolate (SPI) were used to develop SPI-SDF complex coacervates and used as the shell materials of SPEO. The optimal conditions for the complex coacervation between SPI and SDF were established to be pH 4.1 and SPI-to-SDF mass ratio of 6:1. SPEO microcapsules showed a spherical shape with an average particle size of 6.79 μm, and had a good dispersion in water. The SPI-SDF complex coacervates showed excellent encapsulation ability as indicated by high encapsulation efficiency (91.33%) and payload (45.19%). Encapsulated SPEO showed good thermal and storage stability, and possessed a slow-release property in model foods. Encapsulation enhanced the antibacterial activity of SPEO while preserving its antioxidant activity. Aforementioned results indicated that this study successfully improved the stability, solubility, and bioactivity of SPEO. This study provided valuable information for utilizing novel carriers to deliver essential oils and improve their defects through complex coacervation and offered a new pathway for the utilization of plant waste.