Wheat starch gelatinization under microwave irradiation and conduction heating

Wheat starch-water dispersions at excess water conditions were heated under mixing to different temperatures by either microwave energy at 2000 W or by conduction heating in order to compare both heating methods. The effects of microwaves and conduction heating on starch gelatinization were evaluated using different techniques; It was possible to obtain the same viscosity for both heating methods but the required time was much shorter for microwaves heated starch dispersions. No unique structures due to the heating method were observed under the microscope. At the beginning of the heating process an increase in the mobility of the starch protons occurred, slightly higher for microwaves heated samples. Likewise, DSC experiments revealed an increase in the enthalpy for short times microwave heated samples. The heating method caused no differences in the mechanism of gelatinization; nevertheless the crystallinity disappeared at a higher rate when heated with microwaves. (C) 2006 Elsevier Ltd. All rights reserved.