Preparation and characterization of a novel porous whey protein concentrate/pullulan gel induced by heating for Cu2+ absorption

Whey protein concentrate (WPC) and pullulan (PUL) were used to prepare a hydrogel (WPC/PUL) as a novel Cu2+ adsorbent. The scanning electron microscopy, rheology, zeta-potential, sulfhydryl groups, surface hydrophobicity, infrared spectroscopy and thermal gravimetric analysis measurements were used to characterize WPC/PUL. The results showed the mechanism of gel formation may depend on the combination of electrostatic interaction, disulfide bond, hydrophobic interaction and hydrogen bond. The drying kinetic test was taken, and the drying process of WPC/PUL followed Page Model and the activation energy was 56.73 kJ/mol. Furthermore, WPC/PUL was used as a Cu2+ adsorbent and the absorption can reach more than 98% of the equilibrium adsorption (Q(e)) after shaking in Cu2+ solution for 10 min and Q(e) based on the pseudo-second-order kinetic model was 81.66 mg/g. Because the materials were safe and non-toxic, WPC/PUL could be used as a Cu2+ adsorbent during the food industry production process in the future.