Abstract:
In this study, a cold setting gel system of whey protein isolate (WPI) was constructed by the combined treatment of ethanol and transglutaminase (TG). It was characterized by scanning electron microscope (SEM), confocal laser scanning microscopy (CLSM) and fourier transform infrared spectroscopy (FT-IR). The rheological, functional and thermodynamic properties of the gel were investigated,and the formation mechanism of the gel was clarified. The results showed that ethanol and TG could increase the ratio of α-helix and β-fold in the secondary structure of WPI, respectively. The concentration of ethanol and TG had important effects on the stability and viscoelasticity of WPI gel. When the volume fraction of ethanol was 40% and the activity of TG was 120 U/g, the WPI gel with dense network structure and high viscoelasticity was formed, which exhibited strong water holding capacity, high energy storage modulus and apparent viscosity. The heat curves showed that ethanol could reduce the thermal denaturation temperature of WPI, and the presence of TG improved the thermal stability of WPI gel to a certain extent. It was shown that the properties of WPI gel treated with ethanol and TG were better than those of WPI gel treated with ethanol alone. Compared with the traditional preparation methods of WPI gel, the new method had practical production significance of reducing energy consumption as well as improving quality and efficiency. At the same time, it could also meet the diversified needs of new protein gel food.
