Water chestnut, rice, corn starches and sodium alginate. A comparative study on the physicochemical, thermal and morphological characteristics of starches after dry heating

Water chestnut (Trapa bispniosa), rice and corn starch were modified with sodium alginate and subjected to dry heating for 0,2 and 4 h for at 130 °C. The physicochemical, thermal and morphological properties of native as well as modified starches were determined. Thermal and morphological properties were studied using Differential Scanning Calorimeter (DSC) and Scanning Electron Microscopy (SEM). It was observed that the dry heating of starches with and without sodium alginate significantly reduce the swelling power, solubility, paste clarity whereas, water absorption and syneresis increased. The swelling power was higher for corn starch as compared to other starches while rice starch has higher syneresis. In the presence of sodium alginate the water absorption was increased in all starch samples upon heating. The onset temperature was found to be increased after dry heating of all starches. The maximum increased was noticed for rice starch. Morphological studies showed the damaging of granule surface with the accumulation of leached amylose and gum but total degradation was not observed. Peak viscosity, final viscosity, breakdown, and setback of RS- sodium alginate mixture were reduced on dry heating. Although pasting temperature of rice starch was not significantly changed.