EFFECT OF DIFFERENT DRYING METHODS ON MINT LEAVES PHYSICAL AND QUALITY PROPERTIES

Abstract

Three drying methods were used for drying mint leaves, oven drying (40, 50, 60 and 70 o C), microwave drying (180, 360, 540, 720 and 900 Watt) and direct solar drying with three levels of load (0.5, 1.25 and 5kg/m 2).The drying characteristics and the quality aspects of the dried mint leaves were studied. From initial moisture content (7.65 g.w/g.d.m.) to achieve the equilibrium moisture content the drying time was 5 minutes by microwave drier at use powers 900 and 720 Watt with loading level 0.5 kg/m 2 , while the highest time took for drying mint was 20 hours to achieve equilibrium moisture content when use oven drier at 40 o C. Meanwhile, the solar drier required 8 hr. to achieve the final moisture content of mint leaves (0.11 g. w./g. d .m) at both 1.25 and 0.5 kg/m 2 loading levels. The results showed that drying of the mint leaves at temperature 50 o C with loading rate 1.25 kg/m 2 was the best treatment from all treatments were studied in this work to getting the highest amount of essential oil. Midili-kucuk, model adequately described the oven and solar drying behaviors and logarithmic model adequately described the microwave drying behaviors.