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

Abstract

BACKGROUND 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. RESULTS 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+, Ca2+, 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). CONCLUSION 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.

Potassium Chloride as an Effective Alternative to Sodium Chloride in Delaying the Thermal Aggregation of Liquid Whole Egg

“…Each sample was diluted to a concentration of 0.1-0.5 mg/mL using PBS (10 mmol/L, pH 7.2). Endogenous fluorescence measurements were performed utilizing an excitation wavelength of 280 nm, a scanning range from 300 nm to 450 nm, and a slit width of 5 nm [19].…”

“…α-Helices are stabilized by intramolecular hydrogen bonds between the carbonyl (-CO) oxygen atom and the amino (NH-) hydrogen atom of the polypeptide chain. This structural motif is buried within the protein and exhibits amphiphilic characteristics with both hydrophilic and hydrophobic regions, which contribute significantly to the stability of the apolipoprotein structure [19]. β-Sheet structures are typically stabilized by intermolecular hydrogen bonds, while β-turns are located on the surface of proteins, particularly globular proteins, and contain polar and charged amino acid residues.…”

“…Furthermore, the reduction in β-turn content implies a decrease in protein hydrophilicity, potentially due to the exposure of nonpolar amino acids. Heating facilitates the transition from β-turns to random coils, leading to the disruption of weak hydrogen bonds and protein denaturation [13,19]. The observed changes in protein structure and increased aggregation may be attributed to protein-lipid interactions.…”

“…Compared to the control, the addition of KCl resulted in a λ max closer to 330 nm and therefore a blueshift in the peak of endogenous fluorescence absorption. This implies that K + and Na + ions may induce the aggregation or recombination of exposed hydrophobic groups, leading to a more hydrophobic and less polar microenvironment surrounding tryptophan residues [19].…”

A review on the development of pickled eggs: rapid pickling and quality optimization

“…Therefore, it is not only theoretically possible to use potassium salt instead of sodium salt for salted eggs, but it is also more beneficial to health. Compared with magnesium, calcium, and zinc salt, sodium and potassium salt have no significantly different effect on the pickling process of salted eggs, and the changes in the relevant physicochemical indicators are not significant ( Tian et al., 2022 ). Therefore, potassium salt is a viable alternative to the sodium salt in the processing of salted eggs.…”