Microwave extraction of mint essential oil – Temperature calibration for the oven

• Calibration measurement is important to verify the actual capacity of the oven.
• Temperature is a parameter that can influence the microwave extraction efficiency.
• A fiber optic thermometer was used to accompany the temperature profile.
• Suitable models were fitted to experimental data to obtain stable temperature.
• The suggested models were in excellent agreement with the observed data.

The efficiency of the microwave extraction process is linked to the control of many parameters, such as, temperature and extraction time. The objective of this work was to calibrate the microwave reactor unit for uses in different conditions of temperature and time of extraction. The research also includes a microwave extraction as an application of the procedure developed. Ethanol and hexane (3:7 v/v) were used as the solvent and the calibration was based on the calorimetric method. Microwave extraction was carried out using mint dried leaves and its essential oil was analyzed by GC/MS. As a result, time of extraction could be predicted for adjusted models – rational and linear equations, correlation coefficients of 0.998 and 0.999, respectively – and temperature maintained stable in the microwave oven unit, during extraction. Carvone was the major compound obtained by microwave extraction (0.011–0.091% d.b.).