Effect of Hofmeister series anions on freeze-thaw stability of emulsion stabilized with whey protein isolates

The effect of Hofmeister series anions at different concentrations on the freeze-thaw (FT) stability of emulsions stabilized with whey protein isolate (WPI) and its possible mechanism were studied. The emulsions prepared from WPI added with kosmotropic ions (Cl- and Br- ) presented good freeze-thaw stability, whereas those without NaCl were destabilized after freeze-thawing. In addition, the adsorbed protein (AP) percentage, protein load (tau), apparent viscosity, and mechanical moduli of emulsions added with Cl- and Br- were increased with the salt addition, thus facilitating the formation of elastic gel network structure in the emulsion system. WPI added with NaCl exhibited high interfacial pressure (pi) and diffusion rate (Kdiff), indicating that its interfacial behavior promoted the stability of oil-water interface. During the adsorption process, the relative abundance of transferrin (TRF) and immunoglobulin (Ig) of WPI was increased, suggesting their higher interfacial affinity at the interface. After three FT cycles of the emulsion prepared from WPI added with Cl-, the proteins with low molecular weight (LMW) presented better emulsification activity. The decreased relative abundance of TRF and Ig due to the extrusion of the ice crystals would be responsible for the instability of the WPI-stabilized emulsion by freeze-thaw treatment.

Automated summary

This study investigated the effect of Hofmeister series anions at different concentrations on the freeze-thaw stability of emulsions stabilized with whey protein isolate (WPI) and explored the possible mechanism. The results showed that the addition of kosmotropic ions (Cl- and Br-) improved the freeze-thaw stability, while the emulsions without NaCl became unstable after freeze-thawing. The addition of Cl- and Br- increased protein load, apparent viscosity, and mechanical moduli, promoting the formation of an elastic gel network structure. WPI added with NaCl exhibited higher interfacial pressure and diffusion rate, enhancing the stability of the oil-water interface. Moreover, the emulsion prepared from WPI added with Cl- showed improved emulsification activity of low molecular weight proteins after freeze-thaw cycles.