Microwave finish drying of (tapioca) starch pearls

Starch pearls are extremely sensitive to the rate of drying. Fast drying leads to poor quality of final cooked (rehydrated) products. The objectives of this study were to reduce the lengthy drying time by incorporating low-power microwave finish drying and to evaluate the rehydrated quality of starch pearls. The effects of temperature and relative humidity on the drying rates of starch pearls in the constant-rate period were determined. When evaluating the saving of time, microwave energy efficiency and rehydration quality, the best results were obtained when combined natural convection and microwave finish drying were carried out at low power levels (119-143 W). Microwave finish drying reduced the natural convective drying time by about 50-75%, with an improvement in quality, as indicated by higher unbroken ratio, less cooking loss and shorter cooking time.