Crosslinked and stabilized in-kernel heat-moisture-treated and temperature-cycled normal maize starch and effects of reaction conditions on starch properties

Kernels of normal maize were subjected to a heat-moisture treatment (HMT) followed by a temperature cycling (TC) regime that was previously shown to produce slowly digesting starch (SDS) and resistant starch (RS) (Wongsagonsup, Varavinit, & BeMiller, 2008). This starch (in-kernel HMT-TC normal maize starch [NMS]) was then subjected to a low level of crosslinking with phosphoryl chloride, to hydroxypropylation, and to crosslinking followed by hydroxypropylation to determine if it could be converted into a slowly digesting modified food starch. Five controls were used. Digestibility after cooking, RVA parameters, and DSC parameters of gelatinization and retrogradation were determined. Crosslinked in-kernel HMT-TC NMS had the greatest amount of SDS, but only 3.1% (compared to 1.3% in the native starch). Hydroxypropylated and crosslinked and hydroxypropylated in-kernel HMT-TC NMS had the greatest amount of RS, but only 35% and 33%, respectively (compared to 16% in the native starch). Derivatization changed the physical properties of in-kernel HMT-TC NMS. It was also found that subjecting the starches used in this study to the time, temperature, pH, and salt concentration conditions used for derivatization made significant changes to the physical properties of the starch. In fact, subjecting in-kernel HMT-TC NMS and HMT-TC laboratory-isolated NMS to the conditions used for derivatization but without any added reagent made greater changes in the peak viscosity than did derivatization. The same was not true, however, for laboratory-isolated NMS. And for the most part, the starches subjected to the conditions of derivatization alone also produced different final viscosity values, indicating that whatever changes in granule structure and behavior occurred as a result of treatment with reaction conditions were carried through the RVA cooling cycle.