Optimal Condition and Drying Kinetic Modeling of Betel Nut Drying Using Combined Thermal Energy

Abstract

Dried agricultural products are considered as economically important of Thailand. Most of dried agricultural products are still produced using natural sun drying method. Although, it is the cheapest method, dried products are usually contaminated by insects, birds and animals. The objectives of this research were to determine the optimal condition and drying kinetic modeling for drying Betel nut using hot air, microwave and hot air-microwave combination at the air flow rate of 1 m/s. The experimental was done at the air temperature range of 60-80oC and microwave power of 180-600 W. The results showed that the drying rate of Betel nut using hot air combine with microwave was higher than the of using hot air and microwave only. The drying condition at microwave power of 450 W and air temperature of 80oC was found to be suitable for the drying method. The final moisture content of Betel nut was 9.43% d.b. as compared to initial moisture content of 85+5% d.b. The calculation data from the Page model is reasonable for describing drying kinetics of Betel nut.