Effect of salt ions on mixed gels of wheat gluten protein and potato isolate protein

The effects of different concentrations of sodium chloride and calcium chloride on mixed gels comprising wheat gluten (WG) protein and potato protein isolate (PPI) were investigated in this study by measuring texture properties, water holding capacity, rheological properties, hydrophobicity, secondary structure, and microstructure. The objective of the experiments was to elucidate the mechanisms underlying the effect of salt ions on mixed gels and to understand the effect of substituting sodium ions in food applications. The results showed, with the amount of calcium chloride increased from 0 g/mL to 0.004 g/mL or the amount of sodium chloride increased from 0 g/mL to 0.001 g/mL, the water holding capacity, texture properties, α-helix and β-sheet of the WG/PPI gel system increased, but the hydrophobicity and the β-turn decreased concurrently. Furthermore, the scanning electron microscopy showed that the three-dimensional structure tended to be stable. Nevertheless, if the concentration of added ions was increased any further, the opposite tendency was observed. The results indicated that adding the appropriate concentrations of salt ions could induce its structure more compact. However, once the threshold concentration is exceeded, it would limit the stability of the mixed gel network.