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

Abstract

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.

Exergy and Energy Analyses of Microwave Dryer for Cantaloupe Slice and Prediction of Thermodynamic Parameters Using ANN and ANFIS Algorithms

“…By reducing this time, the energy consumption also decreased [49]. In a study by Azimi-Nejadian and Hoseini [47], a specific energy consumption between 0.68 to 2.59 MJ/kg was obtained for drying potatoes in a microwave dryer at power range of 200-800 W. In another study, Khan et al [50] reported specific energy consumption for drying fenugreek leaves in various MW powers (30 to 100 W) in the range of 1.86-2.47 MJ/kg. Furthermore, the energy required to remove one kilogram of water from the cantaloupe pieces during the microwave drying process significantly increased (with a probability level of 5%) by enhancing the thickness of the samples.…”

Postharvest Microwave Drying of Basil (Ocimum basilicum L.): The Influence of Treatments on the Quality of Dried Products

“…Using drying techniques under environmental conditions is applicable only in the presence of favorable climates, i.e., in sunny and breezy areas such as tropical and sub-tropical countries where, moreover, the rural economy is still present [ 4 ]. Mild environmental temperatures prevent the loss of heat-sensitive compounds, but stabilization in this way can require long waiting times, which can favor increases in metabolic and enzymatic reactions in postharvest products, and also damages caused by weeds [ 4 , 5 ]. Moreover, large surfaces are needed and, finally, drying treatment could not be uniform, increasing the risk of contamination.…”

Energy Systems and Applications in Agriculture

“…Comfort for human beings was assessed from the viewpoints of Fanger's predicted mean vote (PMV) and predicted percentage of dissatisfied (PPD) [50,51]. Equations ( 18)- (22) were used to calculate the PMV and PPD.…”