Holy Basil Leaves Drying using Combined Microwave and Hot Air Conveyer Belt Dryer
Keywords:Holy basil leaves, Hot air drying, Microwave-hot air drying, Specific energy consumption
Holy basil is an important ingredient of Thai food. However, it cannot preserve for a long time since the use of a suitable drying process is necessary to prolong the shelf-life of holy basil. This research aimed to investigate the drying kinetics, specific energy consumption and quality (in term of color) of dried holy basil leaves using a microwave-hot air conveyer belt dryer. The holy basil leaves was dried at temperature range 60 to 80°C and microwave powers range 300 to 500 watt. Air velocity was set at 0.3 m/s with 80% of recycled air while the belt conveyor velocity (forward-backward) was 0.02 m/s. The results showed that the rate of moisture reduction increased with an increase in drying temperature and microwave power. For hot air drying, it was found that the lightness (L*) and yellowness (b*) decreased with an increase in temperature. For microwave-hot air drying, the L* and b* value increased with and increased in microwave power. The specific energy consumption decreased with an increase in the microwave power. Based on this experiment, the optimum condition for holy basil drying using microwave-hot air drying was the use of an air velocity 0.3 m/s, temperature of 80oC and microwave power of 500 watt (2x250 W).
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