Physicochemical properties and oil-water interfacial behavior of subcritical water-treated coconut (Cocos nucifera L.) globulins

Abstract

Except for conventional heat treatment, subcritical water treatment also has been applied in the modification of protein. In order to find out whether subcritical water treatment can improve the emulsification property of coconut globulin (CG), the effects of physicochemical properties and interfacial behavior on the emulsifying properties of subcritical water-treated (120 °C for 20 min) CG were investigated and compared with conventional heated (90 °C for 20 min) CG. The solubility of 90°C-CG and 120°C-CG was 72.24% and 81.92%, respectively. Compared to 90°C-CG, the 120°C-CG has smaller size and higher surface hydrophobicity. The 120°C-CG showed higher conformational flexibility which corresponded to the higher interfacial adsorption and viscoelasticity. In addition, the 120°C-CG displayed higher emulsifying stability but lower emulsifying activity than 90°C-CG due to the lower interfacial thickness. Moreover, the 120°C-CG showed higher strain softening under higher amplitude perturbation and higher instability index after centrifuging. However, the emulsion stabilized by 120°C-CG also displayed higher viscosity and more compact transmission profiles, which is conducive to the emulsion stability. This study demonstrated that the subcritical water could effectively modify the structural and emulsifying stability of CG, which is suitable for the application in food industries.