Microwave-assisted drying of Cymbogopon nardus leaves: Kinetics, moisture diffusivity, energy, and emission study

Abstract

The essential oils extracted from Cymbopogon nardus (C. nardus) leaves have a distinct fragrance containing citronellal, citronellol, and geraniol, which has led to their extensive use in the pharmaceutical and perfume industry. The potential of C. nardus might be limited by the short shelf life due to high moisture content, thus a drying process and kinetics analysis is vastly researched to preserve the beneficial compound longer. A microwave-assisted drying method in the present study was analysed by the calculation of the effective moisture diffusivity, activation energy, CO2 emission, and specific energy consumption (SEC) at various microwave power levels (136, 264, 440, and 616 W) and foliage leaf mass (5, 10, 15, 20, and 25 g). Through ten different drying kinetics model fitting and validated by five statistical parameters, Jena-Das model showed the best fit to the foliage drying at various mass and microwave powers. Effective moisture diffusivity was found to increase with microwave power and decrease with decreasing mass. The drying of C. nardus leaf resulted in Ea = 38.6299 Wg-1 in variation of microwave power and Ea = 9.1592 Wg-1 in variation of foliage mass. The lowest CO2 and SEC emissions were found at power of 616 W. Thus, according to mass variation, the lowest CO2 values are at 5 g mass and 20 g SEC. These findings may encourage the development of material analysis in industrial drying technologies to support the availability and quality of specific products.