Effects of salts on the freeze-thaw stability, gel strength and rheological properties of potato starch.

The objective of this study was to evaluate the effects of different salts (NaF, NaCl, NaBr, NaI, K2SO4, KCl, KNO3, KSCN, LiCl) on freeze-thaw stability, gel strength and rheological properties of potato starch. Addition of the structure-making (salting-out) ions, such as F- and SO42-, decreased freeze-thaw stability and increased gel strength, maximal storage modulus (G') and maximal loss modulus (G″) of potato starch, due to a stronger three-dimensional network by promoting the starch retrogradation and inhibiting starch gelatinization. Shear stress versus shear rate of all samples at 25 °C was well fitted to the simple power-law model with high determination coefficients (R2 = 0.9863-0.9990). Flow behavior index (n), consistency index (K) and apparent viscosities increased with adding salting-out ions. However, the structure-breaking (salting-in) ions had reverse effects on freeze-thaw stability, gel strength and rheological characteristics of potato starch. The addition of structure-breaking ions, such as Br-, NO3-, I-, SCN-, Na+ and Li+, decreased gel strength, G' and G″ values and increased freeze-thaw stability. Salts could significantly influence on the retrogradation of potato starch, generally following the ion order: F- > SO42- > Cl- > Br- > NO3- > I- > SCN- for anions and K+ > Na+ > Li+ for cations, consistent with the Hofmeister series.