Effect of different valence metal cations on the gel characteristics and microstructure of Inca peanut albumin gels

In this paper, the effects of different concentration (0.05-0.5 M) of metal ions (Na+, K+, Ca2+ and Al3+) on the gel properties and microstructure of Inca peanut albumin (IPA) were investigated. Results showed that the formation of IPA gel network was mainly in the cooling stage. The hardness, water holding capacity (WHC) and energy storage modulus of the gels increase when the NaCl and KCl concentration are lower than 0.1 M. With the increase of CaCl2 concentration, the hardness and energy storage modulus of the gels first increased and then decreased, but the WHC did not change significantly. Moreover, 0.1 M AlCl3 increased the WHC, surface hydrophobicity and Zeta potential of the gels, but the average particle size decreased. The above results indicate that different metal ions have different effects on the properties of IPA gels. Metal ions induced the interconversion of the IPA secondary structure, in which the increase in the content of beta-sheet structure might be one of the reasons for the enhanced gel properties. NaCl, KCl and CaCl2 induced the gels to form a tighter and more homogeneous fine-chain structure, whereas AlCl3 induced the IPA gel network to form a "sheet-like" structure. In conclusion, the gels' microstructure and properties were improved by the low concentration of NaCl and KCl (<0.1 M), and the gels' distinctive lamellar structure created by 0.1 M Al3+ was better suited to improving their WHC. These results will provide a valuable basis for the application of IPA gels in food colloids.