Starch gelatinization using sodium silicate: FTIR, DSC, XRPD, and NMR studies

The chemical and physical modifications of native maize starch subjected to treatment with aqueous Na silicate have been investigated. The application of FTIR, DSC, XRPD, and NMR analysis is discussed herein with respect to the interaction of Na silicate with starch in relation to gelatinization. XRPD results indicate that Na silicate, in the ionized form, disrupts the molecular structure of starch in a manner similar to thermally induced starch gelatinization. In addition, Na silicate forms new CO–O–SiO2Na moieties with the amylopectin starch component. This was ascertained by the detection of the in‐plane vibration of the –Si–O as a distinctive FTIR band at 580–600 cm−1 and the appearance of a new carboxyl group (–COOH) NMR chemical shift at 168 ppm for the amylopectin/Na silicate system. DSC analysis showed two adjacent endothermic transitions at 192 and 198°C for starch/amylopectin treated with Na silicate whereas amylose treated with Na silicate did not show any new endothermic/or exothermic transitions.