Effect of Sodium Chloride on Glassy and Crystalline Melting Transitions of Wheat Starch Treated with High Hydrostatic Pressure: Prediction of Solute‐induced Barostability from Nonmonotonic Solute‐induced Thermostability

Abstract

AbstractWheat starch was high hydrostatic pressure (HHP)‐treated in aqueous solutions with various sodium chloride (NaCl) concentrations (0 to near‐saturation), in order to explore the effects of salt on glassy and crystalline transitions of starch during the treatment, using differential scanning calorimetry (DSC). For wheat starch at atmospheric pressure, glass and crystalline melting transitions of amylopectin (reported as gelatinization peak temperature) increased up to 2 M NaCl, and then decreased with further increase in NaCl concentration, but the gelatinization peak temperature was higher in all NaCl solutions than in water alone. In contrast, the melting transition for the amylose‐lipid complex (reported as peak temperature) increased continuously with increasing NaCl concentration. When 50% (w/w) starch slurries were HHP‐treated in water and various NaCl concentrations (0.1, 2 and 5 M) for 15 min at 25°C, the presence of salt significantly protected glass and crystalline transitions of starch during the HHP treatment. Although the baroprotective effect was maximal near the lyotropic 2 M NaCl concentration [1‐5], all NaCl concentrations were more baroprotective than was water alone for HHP‐treated wheat starch. As reported previously [6] for corn starches in a lyotropic concentration of NaCl (ionic solvent) or a non‐equilibrium concentration of sucrose (glass‐forming solvent) [7], solute‐induced thermostabilization of the wheat starch gelatinization transition predicted solute‐induced barostabilization.