Re-examination of the interactions between starch and salts of metals from the non-transition groups

The interactions between potato starch and the salts of alkali-earth metals and lead were examined by using scanning electron microscopy/energy dispersive spectroscopy (SEM/ EDS), differential scanning calorimetry (DSC), O-17 and Cl-35 NMR. For the starch blended with saturated solutions of the salts, gel-like, shear-thinning or semi-solid appearances were observed in relation to the ion property of the salts. The volume of saturated salt solutions required for producing shear-thinning properties correlated significantly with the property of anions. SEM and EDS studies on the starches after soaking in 0.5 M salt solutions suggest that both divalent cations and accompanying anions of the salts penetrated into the granule during soaking treatments. Also, the cations (especially Mg2+ and Pb2+) and anions both displayed some influence on the onset (T-o) and peak (T-p) temperatures as well as the enthalpy change (DeltaH) during thermolysis of the starches. From these results and NMR data, the major ion species (anions or cations) interacting directly with starch could be elucidated partially with respect to the salt variety and concentration and preparation condition. The roles of free water content and water structure in the physical characteristics of the starch systems examined were negligible.