Solar drying of selected vegetables

Experiments were conducted to study the drying behaviour of common vegetables grown in Punjab using solar heat during the months of December and January. Fresh cauliflower, potato, onion and spinach were procured from the market and dried in a locally fabricated low cost solar dryer. After preparing the vegetables they were treated suitably for subsequent drying. It took 22 - 24 hrs of solar heat exposure for the drier to reduce the moisture content of the vegetables, from initial values of 257.14% db (min.) - 931% db (max.) to final value in the range of 10.62% db - 46.36% db, till equilibrium conditions were established. The drying occurred in falling rate period for all the vegetables with its moisture content reducing non- uniformly with time. The drying rate (g/min) for these vegetables generally followed exponential decay with drying constant varying from 0.002 to 0.003.