Effect of microwave radiation on physico-chemical properties and structure of cereal starches

Wheat, corn and waxy corn starches of intermediate moisture content (30%) were subjected to microwave processing and the effect of microwave radiation on physico-chemical properties and structure of cereal starches was studied. The experimental starches were examined by the Brabender rheological method, light microscopy, X-ray diffractometry and differential scanning calorimetry. Microwave radiation was evidenced to cause a shift in the gelatinisation range to higher temperatures, and a drop in solubility and crystallinity. The extent and type of these changes depended on the variety of starch. Normal corn and wheat starches underwent pronounced changes, whereas under the same conditions waxy corn starch was almost unchanged. It was concluded that susceptibility of different starches to changes due to microwave irradiation depended not only on their crystal structure, but also on their amylose content.