Performance Evaluation and Quality Attributes of Fruits and Vegetables Dried in a Low-Cost Solar Dryer

Solar drying offers a potentially accessible strategy for reducing post-harvest losses in regions with limited access to conventional energy and preservation infrastructure. This study developed a low-cost solar dryer from locally available materials and evaluated its thermal performance, drying kinetics, and effects on the physicochemical and nutritional quality of tomato, carrot, and orange. During operation, drying temperatures varied from approximately 43.9 to 60.7 °C. Thermal efficiency ranged from 40.34% to 44.32%, while drying efficiencies reached 95.11%, 84.89% and 79.33% for tomato, carrot and orange, respectively. Moisture approached equilibrium after approximately 15–18 h for tomato and carrot, and 24 h for orange. The equilibrium-adjusted Newton model adequately described the drying curves (R2=0.9822–0.9893), with drying constants of 0.1661, 0.1518 and 0.0765 h-1 for tomato, carrot and orange, respectively, confirming the greater resistance of orange to moisture removal. Solar drying produced food-dependent changes in pH, titratable acidity and soluble solids. When mass-dependent compositional results were expressed on a dry-matter basis, substantial nutrient losses became evident. Lycopene in tomato decreased significantly from 157.93±68.99 to 17.96±3.35 μg 100 g-1 dry matter, corresponding to an 88.6% reduction (p=0.0247). Vitamin C decreased from 1412.37±18.91 to 232.26±24.60 mg 100 g-1 dry matter in carrot and from 1430.36±182.69 to 245.37±16.37 mg 100 g-1 dry matter in orange. Processing condition significantly affected vitamin C (p<0.0001), whereas food type and its interaction with processing condition were not significant. The dryer therefore achieved effective moisture removal, but optimization of temperature, airflow, and exposure time is required to improve the retention of thermolabile nutrients.