Re-examination of the interactions between starch and salts of metals fromthe 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 disper sive spectroscopy (SEM/ EDS), differential scanning calorimetry (DSC), O-17 and Cl-35 NMR. For the starch blended with saturated solutions of the salt s, gel-like, shear-thinning or semi-solid appearances were observed in rela tion to the ion property of the salts. The volume of saturated salt solutio ns required for producing shear-thinning properties correlated significantl y with the property of anions. SEM and EDS studies on the starches after so aking in 0.5 M salt solutions suggest that both divalent cations and accomp anying anions of the salts penetrated into the granule during soaking treat ments. Also, the cations (especially Mg2+ and Pb2+) and anions both display ed 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 thes e results and NMR data, the major ion species (anions or cations) interacti ng directly with starch could be elucidated partially with respect to the s alt variety and concentration and preparation condition. The roles of free water content and water structure in the physical characteristics of the st arch systems examined were negligible.