Cereal Chem 62:447-453   |  VIEW ARTICLE
Model Wheat Starch Systems Heated by Microwave Irradiation and Conduction with Equalized Heating Times.

B. J. Zylema, J. A. Grider, J. Gordon, and E. A. Davis. Copyright 1985 by the American Association of Cereal Chemists, Inc. 

A structural comparison of starch gels prepared by either microwave irradiation or by convection heating in an oil bath was made. The heating time in each paired comparison was kept constant to minimize any difference caused by the rate of heating. Starch to water ratios ranged from 1:1 to 1:8. Wheat starch granule swelling was evaluated by scanning electron microscopy and polarizing light microscopy, and residual crystallinity was determined by differential scanning calorimetry. Time-temperature profiles for the two heating methods differed even though the total times to reach 65 or 85 C for each starch-water ratio were essentially equal. The distribution of variously swollen granules and the range in degree of swelling within the samples depended on the heating method and subsequent heat transfer. No structures unique to a given heating method were found. Residual crystallinity was found in swollen but birefringent granules. Onset temperatures of endotherms for these granules did not differ from those of the unheated starch granules.