Hofmeister Effect on Gel and Rheological Properties of Soy Protein Isolate

Abstract

In this study, the effects of four Hofmeister salts (KCl, NaCl, CaCl2 and MgCl2) at different concentrations (0.02, 0.04 and 0.06 mol/L) on gel properties and rheological properties of soy protein isolate (SPI) were systematically explored. The results showed that the addition of salt ions could improve the gel strength of SPI, but higher concentrations (0.04 and 0.06 mol/L) of CaCl2 and MgCl2 reduced the gel stickiness of the samples. In the dynamic rheological test, each salt ion increased the storage modulus (G’) and loss modulus (G”) of the samples to varying degrees. Higher concentrations of CaCl2 and MgCl2 caused excessive aggregation of SPI, whereas lower concentrations of CaCl2 and MgCl2 exerted an opposite effect. In the temperature sweep test, CaCl2 and MgCl2 changed the trend of G’ and G”, while KCl and NaCl simply increased G’ and G” without changing their trend. In the steady rheological test, higher concentrations of CaCl2 and MgCl2 reduced the apparent viscosity and shear force of the samples, while an opposite effect was observed under the other salt conditions. The decreasing order of the effects of higher concentrations of salt ions on the apparent viscosity and shear force was K+ > Na+ > Mg2+ > Ca2+. In summary, at specific salt ion concentrations (0.04 and 0.06 mol/L), the changes in gel and rheological properties of SPI were consistent with the Hofmeister effect.

Keywords

• soy protein isolate; rheology; gel; hofmeister effect