In this article,the microwave irradiation of tapioca starch (produced in the province of Guangdong,China,moisture content 15%) was carried out in open and sealed systems with the 280W microwave power. Figure shows the rheological properties of irradiated tapioca starch in open. The investigation suggest that, either in open or in sealed, the storage modulus (G') and loss modulus (G'') of the tapioca starches increase to a maximum and then drop during heating both raw starch and irradiated samples. As compared to raw starch, the irradiated starches both in open and sealed showed a higher gelatinization temperature (TG') and peak G', but a lower peak tangent delta. Moreover, for all irradiated samples, the starch irradiated 5 min showed a highest peak G', breakdown in G' and peak tangent delta values. These observation points to microwave irradiation affect the rheological properties of tapioca starch significantly.

Acknowledgment: We gratefully acknowledge the financial support from the NSFC (project 20436020 and 50573025).

Figure The relationship between the temperature and the storage modulus (G') (a) and the loss modulus (G'') (b) of irradiated starch in open.