We studied herein the effects of high hydrostatic pressure on the physical properties of capsicum oleoresin encapsulated with globular protein, such as whey protein isolates (WPI), soybean protein isolates (SPI), and casein protein (CSP). After pressurization at 0.1, 100, 200, and 300 MPa with various concentrations (0.1, 1, 2, and 5 wt%) of proteins, the particle size, ζ-potential, and interface tension were evaluated. Furthermore, the encapsulation efficiency (EE), release study, and morphology were investigated to study the effects of high hydrostatic pressurization upon emulsion stability. While the pressurized emulsion droplet size of capsicum oleoresin emulsion with the protein decreased, the 0.1 wt% concentration of SPI presented the smallest size at 257.37 nm. The interface tension of all protein emulsions decreased slightly after high-pressure treatment according to the increment of the pressure level. EE (%) of the WPI, SPI, and CSP emulsions increased when the pressure level increased. The lowest EE 48.91% was presented in pressurized WPI emulsion at 0.1 MPa while CSP emulsion at 300 MPa showed the highest EE about 65.76%. Over twelve hours, the core material of the pressurized protein emulsions was released slowly compared to non-pressurized conditions with the WPI and CSP emulsions. At the end of the storage of the WPI and CSP non-pressured emulsions, the remaining amount of encapsulated capsicum oleoresin was only 10% and 40%, respectively, less than emulsions treated under high pressurization. Thus, the high pressurized protein could be a candidate for the encapsulation of the capsicum oleoresin.
Rheological characterization of the thermal gelation of cowpea protein isolates: Effect of pretreatments with high hydrostatic pressure or calcium addition
