Efficient Drying of Holy Basil Leaves Using a Hybrid Microwave and Hot Air Conveyor Dryer

Abstract

Holy basil leaves are a key ingredient in Thai cuisine, but their short shelf life necessitates effective preservation techniques. This study explores the drying kinetics, specific energy consumption, and color quality of dried holy basil leaves using a hybrid microwave and hot air-drying system on a conveyor belt. Drying was tested at 60–80°C with microwave power from 300–500 W. The airspeed was set at 0.3 m/s, with 80% air recirculation, and a conveyor speed of 0.02 m/s. Results indicated that both drying temperature and microwave power significantly influenced the moisture reduction rate, with higher temperatures and microwave powers accelerating moisture removal. In hot air drying, the leaf brightness (L*) and yellow (b*) values increased with rising drying temperature. In contrast, when combined with microwave drying, both the L* and b* values improved with increasing microwave power, while specific energy consumption decreased. The optimal drying conditions for preserving holy basil leaves were determined to be a drying temperature of 80°C, microwave power of 500 W, and an airspeed of 0.3 m/s. These findings suggest that the microwave-hot air hybrid drying method offers an efficient and effective solution for preserving the quality of holy basil leaves while reducing energy consumption.

Keywords: Holy basil leaves, Hot air drying, Microwave-hot air drying, Color quality, Specific Energy Consumption