Abstract
ABSTRACT: Drying of thin layer tomato was studied using a solar tunnel dryer under the ecological conditions of Isparta, Turkey. During drying process, solar irradiation, drying air temperature, relative humidity, and air velocity were measured constantly in different parts of the dryer. Drying runs were performed using plum tomatoes, characterized by an oval shape, intense red color. The change of tomatoes mass was measured daily. The color measurements of dried products were determined at the beginning and end of experiment. In this study, the fresh tomato samples were sorted, graded, washed in water and then sliced into quarters and halves before pretreated. Sun drying behavior of half and quarter sliced tomatoes pretreated with 10% NaCl solution and non-pretreated was investigated. Results showed that the drying time for pretreated and non-pretreated samples was not significantly different. However, drying time and drying rates were affected by number of tomato slices (quarter and half). Drying characteristic curves were evaluated against thirteen mathematical models and the Midilli et al model was the best descriptive model for solar tunnel drying of thin layer tomato. Color analysis emphasized that if tomatoes are pretreated with 10% NaCl solution, they should be sliced in quarter for better quality.
Highlights
Tomato is the second most important vegetable after potato in the world (ABANO et al, 2011)
This study focused on evaluation of the effects of salt pretreatment and slicing tomatoes on the drying process using a solar tunnel dryer in Isparta conditions and to determine the best describing mathematical model to experimental data
More energy received by the collector at the high solar irradiance (Figure 4) led to increase drying air temperature which was equated by the increased air velocity (Bala et al, 2003)
Summary
Tomato (solanum lycopersicum) is the second most important vegetable after potato in the world (ABANO et al, 2011). Tomato production in the world was 1,6 billion tons in 2014 (FAOSTAT, 2015). Drying is one of the important techniques for preservation of agricultural products after harvest and the market share for dried products at high quality is increasing every day due to consumer’ demands. Conventional solar drying, which has been applied on the ground in open air, is the most commonly used method of drying in developing countries, because it is the simplest and the most inexpensive method of conserving foodstuffs (Stiling et al, 2012). Even though conventional solar drying offers inexpensive way of drying operation, agricultural products are exposed to uncontrolled weather conditions and to the attack of insect, pests, microorganisms, and dust
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