Ultrasound-assisted hot air drying characteristics of Phyllanthus emblica

The ultrasound-assisted hot air drying characteristics of Phyllanthus emblica was investigated in this paper. The effects of hot air temperature (60 degrees C, 65 degrees C, 70 degrees C, and 75 degrees C), ultrasonic pretreatment time (2, 4, 6, and 8 min), and ultrasonic power (200, 250, 300, and 350 W) on the drying rate, energy consumption, color change, and rehydration rate were evaluated and compared. It was found that the drying rate of Phyllanthus emblica increased with the hot air temperature. The drying time of Phyllanthus emblica with ultrasonic pretreatment was reduced by 10.0%, 25.0%, 21.4%, and 9.0% at 60 degrees C, 65 degrees C, 70 degrees C, and 75 degrees C, respectively. However, the hot air drying was not proportionally promoted by the increase of ultrasonic power or the extension of pretreatment time. Only an appropriate ultrasonic power or pretreatment time can not only improve the drying rate and rehydration rate, but also reduce the energy consumption and the total color change of the dried samples. A new drying model that considered the influences of hot air temperature, pretreatment time, and ultrasonic power was developed to fit the drying process. The results showed that the new model can accurately predict the hot air drying process of Phyllanthus emblica with and without ultrasonic pretreatment.