Effect of Baking Conditions on Properties of Starch Isolated from Bread Crumbs: Pasting Properties, Iodine Complexing Ability, and X-ray Patterns

In order to understand starch changes induced by baking process at different locations of a slice of sandwich bread, namely the top, center, and bottom locations, starch was isolated from crumbs baked at two heating rates ( 6.31 and 4.67 A degrees C/min) and evaluated for their pasting properties, gelatinization parameters, and iodine complexing ability. Results showed that starch isolated from the bottom and the center crumbs baked at higher heating rate presented the significant higher final viscosity and higher setback than that isolated from crumbs baked at lower heating rate. Thermal analysis showed that starch isolated from the center crumb of the bread slice presented the lower enthalpy value of gelatinization, confirming that these samples underwent higher heat-moisture treatment during the baking process. After equilibration at 0.97 a(w), the exposure to iodine vapor changed the X-ray diffraction intensity of starch samples. Polarized light microscopy showed that heating affects starch granule morphology due to the higher starch chain mobility and the higher granular swelling when breads were baked at lower heating rate.