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Title: Effect of sodium chloride on glassy and crystalline transitions of wheat starch treated with high hydrostatic pressure: Prediction of solute-induced barostability from nonmonotonic solute-induced thermostability

Author
item Kweon, Meera
item SLADE, L - FD POLYMER SCI CONSULT
item LEVINE, H - FD POLYMER SCI CONSULT

Submitted to: Starch/Starke
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/27/2007
Publication Date: 3/1/2008
Citation: Kweon, M., Slade, L., Levine, H. 2008. Effect of sodium chloride on glassy and crystalline transitions of wheat starch treated with high hydrostatic pressure: Prediction of solute-induced barostability from nonmonotonic solute-induced thermostability. Starch/Starke. 60:127-133.

Interpretive Summary: Although all concentrations of NaCl from 0.01 to 5 M caused an increase in the gelatinization peak temperature for wheat starch, compared to water alone, thermostabilization at atmospheric pressure was maximal near 2 M NaCl. HHP treatment of the starch at 25 deg C had a significant progressive impact on glassy and crystalline transitions of starch with increasing pressure, resulting in a progressive extent of gelatinization and annealing. Although HHP treatment in all of the tested concentrations of NaCl from 0.1 to 5 M resulted in a greater retention of amylopectin structure than did treatment in water alone, the barostabilization at 25 deg C was maximal near 2 M NaCl. This study has demonstrated that the concentration-dependent pattern of the solute-induced barostabilization of wheat starch by NaCl at room temperature was predicted by the concentration-dependent pattern of the solute-induced thermostabilization at room pressure, even though the extent of thermostabilization depended nonmonotonically on the concentration of NaCl.

Technical Abstract: Wheat starch was high hydrostatic pressure (HHP)-treated in 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 concentrations than in water alone. In contrast, the melting transition for 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 25C, 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, all NaCl concentrations were more baroprotective than was water alone for HHP-treated wheat starch. As reported previously [1] for corn starches in a lyotropic concentration of NaCl (ionic solvent) or a non-equilibrium concentration of sucrose (glass-forming solvent), solute-induced thermostabilization of the wheat starch gelatinization transition predicted solute-induced barostabilization.