Effect of Particle Size and Transparent Solar Dryer Cover on the Proximate Analysis of Dried Onion

In this work, we investigate effect of particle size and transparent solar dryer cover on the proximate analysis of dried onion. A solar drying unit was developed and constructed for drying the of red onion slices in order to determine the proximate composition of fresh and dried red onion using multi-crop direct solar dryer. Also, the evaluation and effect of particles size and multi-crop transparent solar dryer cover on the proximate analysis of red onion during drying. Consequently, the higher efficiency of the solar collector was obtained at the higher airflow rate. The moisture content of dried onion slices was strongly affected by the thickness of the onion slices and the density of the polyethylene. The final moisture content of dried onion slices ranged from 10.85% to 13.01%, 4.95% to 6.01% ash, 4.69% to 5.26% fibre, 11.17% to 13.09% fat, 6.70% to 5.60% protein and 68.64% to 68.03% carbohydrate for particle sizes of 3 mm, 5 mm and 7 mm dry-basis depending on drying temperature cycle for low density polyethylene cover. While the final moisture content of dried onion slices ranged from 9.85% to 12.01%, 5.96% to 6.01% ash, 3.69% to 4.26% fibre, 13.17% to 12.09% fat, 5.70% to 6.60% protein and 61.64% to 58.03% carbohydrate for particle sizes of 3 mm, 5mm and 7mm dry-basis depending on drying temperature cycle for high density polyethylene cover.