Solar drying of fruits and vegetables: dryers’ thermal performance, quality and shelf life of dried mango, banana, pineapple and tomato
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Date
2013
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Sokoine University of Agriculture
Abstract
The thermal performance of solar drying methods (cabinet direct, cabinet mixed-mode and tunnel drying), biochemical, sensory, rehydration and shelf-life qualities of mango banana, pineapple and tomato varieties were investigated in this study. Collector efficiencies
and drying rates were computed and compared to measure the performance of dryers. The results showed tunnel dryer had significantly (p<0.05) higher efficiency (57.5%) with drying rates of
1.36, 1.17, 1.35 and 1.57 kg/h for mango, banana, pineapple and tomato, respectively than cabinet dryers with efficiency of 32.4-34.2% and drying rates of 0.11-0.13, 0.09-0.11, 0.11-0.13 and 0.17-0.22 kg/h for mango, banana, pineapple and tomato, respectively. Biochemical
values varied significantly (p<0.05) between fresh and dried samples and between drying methods with fresh samples in all fruit and vegetable having higher total phenols (139.3 }2.3-538.9 }1 mgGAE/100g DM), antioxidant capacity (10.8 }0.1-46.8 }0.5 μmol/100g DM), protein (2.8 }1.3-16.5 }1.1 g/100g DM) and vitamin C (28.3-126.8 mg Lasc/100g DM) than dried samples having total phenols, (81.2 }0.5- 675.5 }1.5 mgGAE/100g DM), antioxidant capacity (6.0 }0.2-43.0 }0.4 μmol/100g DM), proteins (2.1 }0.1-13.9 }0.1 g/100g DM) and vitamin C (3.8-65.1 mg Lasc/100g DM). The sensory analysis findings showed that, all fresh samples had significantly higher colour intensity scores of 8.1 than dried counterparts, 6.3-7.8 points, which on the other hand had highest flavour scores. Fresh mango, banana and dried tomatowere the most liked by consumers with colour and flavour attributes 4 being the main drivers for likeness. However, despite the loss, substantial amount of biochemical and sensory parameters were retained in concentrated dry forms except vitamin C. The shelf-life of six and above six months observed for dried vegetable and fruits respectively. Therefore, it can be concluded that tunnel dryer performs better than cabinet dryers. Solar drying has varied significant effects on some quality parameters of dried fruits and vegetables but retains substantial amounts and it has potential to extend shelf life of fruits and vegetables. Therefore, needs for solar drying technology advocacy in the country for reducing the alarming postharvest losses, more research and fabrication of affordable local tunnel dryer comparable to the industrial ones and further studies to ascertain shelf life above 6 months including more parameters are highly recommended.
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Keywords
Solar drying fruits, Vegetables dryers’, Thermal performance, Mango, Banana, Pineapple, Tomato