Hot air assisted Microwave Drying on Moringa leaves, Spinach leaves, Lemongrass, Banana, and Ginger: Drying Characteristics and Antioxidant Activity

Abstract

Moringa leaves, spinach, lemongrass, banana, and ginger have various bioactive phytochemicals, micronutrients, and health-improving pharmacological effects. The main objective of the present study is to dry moringa leaves, spinach, lemongrass, banana, and ginger using a hot air-assisted microwave drier and the effect of microwave power on activation energy, effective moisture diffusivity, drying rate, and antioxidant activity. The hot air temperature is maintained at 50°C with airflow rate is 2 m/s. For moringa leaves, spinach, lemongrass, and ginger, 0.2, 0.4, 0.6 kW microwave power was used. But for banana, 0.35, 0.45, 0.55 kW microwave power was used. Nine drying models were used to validate the experimental data obtained during drying. To get the best fit model, MATLAB software version 11 was used. At 0.6 kW microwave power, effective moisture diffusivity, drying rate, and antioxidant activity increased while activation energy and drying time decreased. The study result revealed that the samples dried at 0.6 kW for moringa leaves, spinach, ginger, lemongrass and 0.35kW for banana showed the highest antioxidant activity. From the result, the study concluded that hot air-assisted microwave drying can be used for drying moringa leaves, spinach, lemongrass, banana, and ginger.