Evaluation of solar-powered cold storage and evaporative cooling system as off-grid methods for postharvest vegetable storage: Evidence from a laboratory experiment in Nigeria

This study examined the postharvest storage potentials of a solar-powered cool storage and an off-grid, metal-in-wall evaporative coolant. Temperature drop and relative humidity (RH) increase were used to analyze the performance of cooling systems. Tomato (United Trading Company (UTC) variety), orange (Dan Benue variety) and carrot (Orange Chantenay) were obtained from the international fruits market in Dutse, Jigawa State, Nigeria. The items were sorted and stored in three different storage conditions: room temperature (RT), solar-powered cold storage, and metal-in-wall evaporative cooling systems. Mass loss, color, hardness, total soluble solids and titratable acids, carotenoids, vitamin C, and rate of nutrient degradation were among the quality indicators tested. The study shows that the solar-powered cold storage outperformed all other storage methods across the evaluated parameters; it preserved fruit firmness, significantly reduced the rate of color change, and minimized mass and nutrient losses, outperforming the metal-in-wall evaporative cooling system. For instance, tomato mass losses observed in 24 days were 42.66, 63.79, and 85.45 percent in the solar-powered cold storage, evaporative coolant, and ambient storage, respectively. Economic advantages of the above technologies, however, require careful consideration of investment costs and longer-term durability and benefits.