Investigation of thermodynamic parameters and essentioan oil content in drying of rosemary by applying a microwave pulsed pretreatment

Today the use of pretreatment operations to reduce time, energy and cost of drying of agricultural products and foodstuffs are taken into consideration. In this study the rosemary herb dried by using the microwave pre-treatment at three treatments (90 W for 5 minutes, 180 W for 5.2 minutes and 360 W for 5.1 minutes) and control treatment (without pre-treatment) in a hot air dryer at temperatures of 40, 50 and 60 °C and were evaluated energy and its thermodynamic parameters. The results showed that the lowest amount of specific energy required and specific heat required occurred at temperature 60 °C and pre-treatment 360 W and the highest value of this parameter occurred at temperature 50 °C and control treatment. Also the highest thermal efficiency and convective efficiency was 64.32 kJ/kg and 33.32% at temperature 60 °C and 360 W pre-treatment and the lowest thermal efficiency and convective efficiency was 5.15 kJ/kg and 11.54% at temperature 40°C and control treatment. Changes in energy and drying efficiency was irregular because of apply microwave treatment but it can be concluded that applying microwave pre-treatment caused reduction heat and total energy consumed. The highest essential oil content was %0.77 and occurred at 40°C by using microwave pretreatment with 360 for 2.5 min, and the lowest essential oil content was %0.21 and occurred at 60°C in control treatment.