Rheological properties and calorimetric analysis on zein under high pressure treatment

To investigate the influence of high pressure treatment on the rheological behavior and thermal property of zein, the rotating viscometer and differential scanning calorimetric (DSC) were employed to obtain the property parameters, including shear stress (τ), shear rate (γ), viscosity (η), crystallization temperature (Tc), melting temperature (Tm), and crystallizationenthalpy (ΔHm). Then their relationship curve and mathematical model were fitted and established by rheological testing and calorimetric analyzing. The structures of zein solution under different high-pressure treatment were characterized by scanning electron microscopy (SEM). The results indicated that the zein solutions with high pressure treatment showed a pseudo plastic fluid characteristic. As the pressure increased, the viscosity of the solution first increased, and then decreased, and then increased once again. When the pressure was 400 MPa, the viscosity of the solution reached the highest value. When the shear temperature increased, the viscosity of the solution first decreased, and then increased, and reached the lowest value at 40℃. With the shear rate increased, the viscosity of the solution reduced, and reached a plateau when the shear rate was close to 100 s-1. Zein powders were treated under 400 MPa pressure, melting temperature(Tm) increased and crystallization enthalpy(ΔHm) decreased. The width of DSC melting peak(Tm-Tc) under high pressure treatment broadened, proving the coordination of zein structure became lower. SEM showed that zein particles under 400 MPa pressure treatment condensed in a ring or chain structure.