DEVELOPEMENT OF A VEGETABLE DRYER

Abstract

A Vegetable dryer of dimension 1.50 m (high) x 0.72 m (wide) x 0.59 m (breadth) was developed using mild steel iron and its performance evaluated. The device consists of a drying chamber with three drying trays; fans incorporated for heat circulation, a heating element of 2000 W, four swivel caster rollers for ease of mobility, a thermostat to regulate the heat generated in the drying chamber and a thermo-gauge inserted to monitor the temperature in the drying chamber. The vegetable dryer has a drying capacity of 34 kg and three compartments of 0.25 m equal spacing. The dryer is partitioned at 0.75 m, 0.1 m and 1.25 m from the heating element, with the first (bottom) tray, the second tray (middle) and the third (upper) respectively. The device performance was evaluated under no-load and load conditions at 50 °C, 60 °C, and 80 °C temperatures with three replications. Results obtained under no-load indicated that temperatures very close to the preset values (by the thermostat) were attained within 5 mins. Under load condition, the dryer was evaluated by drying 16.74 kg of tomatoe slices at 50 °C, 60 °C, and 80 °C. Weight reduction (degree of moisture loss) from the slices was recorded at intervals of 1hour until a nearly constant weight was obtained. The result revealed that the dryer has a mean drying efficiency of 80.6 % and drying rate of 0.02 kg/hr. At a drying time of 10 hours and temperatures of 50 °C and 60 °C, 16.74 kg of tomatoes were reduced to 1.23 kg and 1.13 kg representing 93 % (wb) of removed moisture, while a final weight of 1.08 kg dry matter was obtained from the same starting weight of wet tomatoes at 80 °C representing 94 % (wb) of moisture loss for the same drying time. ANOVA studies indicated that the effect of temperature and tray level on drying of vegetable (tomatoes) were highly significance at (P< 5 %). The dried vegetable (tomatoes) is free from dust and any form of contamination making it healthy for consumption.