Moslem Namjoo

The objective of the present study was to examine the influence of sonication by power ultrasonic waves during thin layer drying of cumin seeds. To achieve this, a lab scale ultrasound assisted air drying unit was developed and built to dry cumin seeds at air temperatures of 30, 35, and 40 ºC, airflow velocity of 0.6, 0.8, 1 m/s, and sonication power of 0, 90, 180 W. The experiments were designed by response surface methodology and drying time, effective moisture diffusivity, energy consumption, color change, and rupture force of the end-product were examined. The key results revealed that the use a physical field processing such as ultrasound increases the drying overall performance in terms of drying time, kinetics as well as quality attributes such as color. The air born sonication process while drying not only enhances the energy efficiency through rise in effective moisture diffusivity but also decreases the energy consumption by almost 40%. It is interesting that the sonication positively correlated with (P-value < 0.0001) the total color change and rupture force of cumin seeds upon drying. The optimum drying condition with the desirability of 0.95 was achieved at air temperature of 39.45 ˚C, velocity of 1 m/s, and sonication power of 180 W. In these optimum conditions, the drying time, effective moisture diffusivity, the energy consumption, total color change, and rupture force were 34.10 min, 3.78 × 10– 9 m2/ s, 0.52 kWh, 8.58 and 26.84 N, respectively. Finally, RSM model validation revealed that the experimentally measured values of drying parameters were in close agreement with the predicted values.