Papain immobilization on interconnected-porous chitosan macroparticles: Application in controllable hydrolysis of egg white for foamability improvement

Herein, we proposed an interconnected-porous chitosan macroparticles (IPCMs) immobilized papain to exactly control the enzymatic hydrolysis degree of egg white (EW) via a non-heating technology in order to improve its foamability. The SEM images showed that the sodium carbonate (Na2CO3) as gas porogen with varying concentration was able to improve the porosity structure of surface layer of interconnected-porous chitosan macroparticles (IPCMs). The activity determination results indicated that the IPCMs prepared with 0.4 M Na2CO3 hold the highest activity immobilized of papain. In comparison with free enzyme, immobilized papain had a higher range of pH and temperature adaptability, as well as the thermal stability. With a limited hydrolysis, the immobilized papain obtained through condition optimization could enhance the foaming capability (FC) and foaming stability (FS) of EW to 646.67% and 71.62%, respectively. The Fourier transform infrared spectroscopy (FTIR), particle size, zeta potential and surface hydrophobicity were used to analyze the molecular structure change of EW after hydrolysis. Importantly, the immobilized papain could control the enzymatic reaction processing via simple separation, ensuring the optimal hydrolysis degree of EW for foamability enhancement, it also prevented the decrease in foamability during storage due to continuous enzymatic hydrolysis.