Design and Modification of Family Size Dryer for Vegetables and Fruits using Hot Water

Abstract

The experimental study was conducted in the Department of Agricultural Engineering, Faculty of Agriculture, University of Cairo, Egypt. The experiment include design of two dryers, hot water and electric candles dryers, . The source of energy is the only difference between their components. Three varieties of horticulture products, bananas, potatoes and onions were selected to test the dryers performance. Three different methods of drying were applied based on the location of fan used inside the drying chamber. (top, bottom or both). The dried products were subjected to many tests. These tests includes drying rate, moisture content, Physical properties (bulk density, water solubility index, rehydration ratio, water absorption index, yield and dehydration ratio) and organoleptic evaluation (color, taste, flavor, general appearance and overall quality). Electric candles dryer gave faster drying rate (5.5 hours ) when using both fans or bottom fan only for banana. For potatoes drying rate; electric candles dryer using top fan gave the faster drying time (4 hours). Electric candle dryer gave faster drying rate when bottom fan was used for onion dried product . The lowest figure scored for potatoes moisture content with electric candles and hot water dryers when bottom fan used 3.25% and 3.33% respectively, while electric candles with both fans gave the highest value for banana 9.89% System of electric candles drying for potato to measure bulk density using top and bottom fans obtained the highest value 1.250 (g/ml). The result of water solubility index measured for different crops showed that, electric candles dryer using bottom fan gave the highest value 71.06(g/100gSM) for banana sample. The tested rehydration ratio of three dried crops; electric candles dryer gave highest value for onion with both fans 6.50. Hot water dryer using top fan gave the highest value 5.55(g.gel/g DM) for potato when water absorption index measured . The best result obtained with hot water dryer using top fan 19.93% for onion yield. The dehydration ratio result of banana indicated that, the hot water dryer using two fans gave the highest value 5.77. When the crops subjected to color evaluation; hot water dryer with two fans had a lowest value 1.29 for potatoes. Onion taste dried by hot water dryer using bottom fan gave the lowest and best value 2.13 among three crops. Onion flavor evaluation gave the best result 2.19 when electric candles dryer with two fans was used. Potatoes general appearance recorded the best result among the tested crops with hot water dryer using both fans 2.24. Overall quality evaluation showed that, hot water dryer using both fans gave the best result 2.18 for potatoes more than banana and onion . The general conclusion for the previous parameters results (bulk density of banana, dehydration ratio of banana, color of potatoes, onion taste, general appearance of potatoes and overall quality of potatoes) indicated that, hot water dryer with top and bottom fans ranking as superior than candles dryer.