Drying mechanism of Indian dark red onion slices at high velocity

Abstract

Drying of onion is a moisture removal process to increase shelf life. Convection drying experiments are conducted at a drying temperature of 50 ℃, 60 ℃, 70 ℃, and at four high airflow velocity (2, 3.6, 5.7, and 7.7 m/s) for Indian dark red onion. The objective is to analyze the drying mechanism of Indian dark red onion slices at high velocity. The work diverges from the literature in analyzing the drying mechanism of Indian dark red onion slices at air velocity above 2 m/s. Moisture content removal curves for upper velocities (i.e., for 5.7 and 7.7 m/s), shows seamless logarithmic in nature. Dehydration process from Indian dark red onion accelerates as velocity increases. Air velocity 2, 3.6, and 5.7 m/s exhibit a better moisture removal rate at 60 ℃ than 50 and 70 ℃. It is observed that the weight basis moisture content per unit mass flow rate of air decreases as velocity increases. The effective moisture diffusivity averagely increases with an increase in air temperature and air velocity. The values for the arithmetic mean of effective moisture diffusivity lies between 1.096646×10-11 to 1.295467×10-11 and activation energy observed in the range of 10.8709 to 12.7719 kJ mol-1.