Effects of different metal ions on the physicochemical properties and microstructure of egg white gel

To ameliorate egg white gel's salinity and undesirable texture characteristics during curing, different metal ions (K⁺ , Mg²⁺ , Ca²⁺ , Zn²⁺ ) were used to replace sodium chloride (NaCl) to simulate salted eggs partially. The effects of these ions on the physicochemical properties, microstructure, and gel characteristics of egg white protein were studied.

Low field nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) analysis showed that adding K⁺ , Mg²⁺ , Ca²⁺ , and Zn²⁺ could decrease immobile water content and increase free water content in egg white gel. Circular dichroism/fluorescence spectrophotometry (CD/FL) analysis showed that substitutive addition of K⁺ , Mg²⁺ , Ca^2+, and Zn²⁺ changed the conformational structure of the protein, which was not conducive to the formation of the three-dimensional mesh gel structure. Differential scanning calorimetry (DSC) results show that the addition of four metal ions could reduce the thermal denaturation temperature of egg white gel. Scanning electron microscopy (SEM) showed that the gel structure of egg white in the zinc chloride (ZnCl₂ ) group was rougher and more chaotic, the crosslinking degree was worse, so it was not suitable for low sodium salted egg preparations. The gel strength of the calcium chloride (CaCl₂ ) group was significantly higher than other groups (P < 0.05), while the gel strength of the potassium chloride (KCl) group was similar to the NaCl group (P > 0.05).

CaCl₂ and KCl could be used as partial NaCl substitutes to study the addition level and ratio further and improve salted egg white quality. © 2021 Society of Chemical Industry.