Microwave assisted drying and extraction technique; kinetic modelling, energy consumption and influence on antioxidant compounds of fenugreek leaves

Fenugreek leaves contains bioactive compounds, which are helpful in maintaining human health. These compounds are adversely affected in conventional drying methods. Therefore, this study was carried out to retain maximum amount of these components through microwave-assisted drying and extraction technique. The technique was optimized for simultaneous drying and extraction process for fenugreek leaves. The drying rate and drying time were influenced by the level of microwave power; time was reduced from 21 to 5 minutes, when microwave power was changed from 30 to 100 W. Unlikely, the drying rate increased from 1.79 to 4.56 ± 0.05 g/(100 g.min) with the change in power (30 to 100 W). Moreover, moisture ratio analysis determined that two term model was the best to demonstrate the fitness with experimental values. The energy consumption was lowest for 100W compared to other powers. Furthermore, comparison between microwave-based extraction and methanol-extraction indicated that the antioxidant activity was better preserved compared to conventional ones even at higher microwave power levels.