Abstract: In this study, a starch-water system was treated with microwave at a cumulative energy of 1 680 J/g of maize starch (MS) and was evaluated for changes in granular morphology, transparency, sediment volume, water absorption capacity, water holding capacity, relative crystallinity and rheological properties. The results showed that the structural integrity and birefringence of the starch granules was weakened with increasing water content in the starch-water system. The transparency, sediment volume, water absorption capacity and water-holding capacity of the starch suspension were significantly increased after microwave treatment. The X-ray diffraction pattern showed that the crystal type (A-type) of the starch granules was not changed while the relative crystallinity was decreased after the microwave treatment, indicating that the microwave treatment destroyed the crystalline structure of the starch. The elastic modulus of the starch suspension was greater than the viscous modulus, indicating the dominance of elasticity, which was not changed by the microwave treatment. These results show that microwave treatment of starch-water systems can significantly affect the granular structure and physicochemical characteristics of starch, which may provide an experimental and theoretical basis for the development of modified starches with unique physicochemical property and for the improvement of starch modification process.

Key words: maize starch; microwave; transparency; rheological property