Effect of Drying Temperature on the Nutritional Quality of Tomato Slices in Kano State

Tomato (Solanum lycopersicum) is a nutritionally significant crop and a major agricultural commodity in Kano State, situated in Nigeria's North West geopolitical zone, where post-harvest losses due to inadequate drying infrastructure remain substantial. This study investigates the effect of varying drying temperatures on the nutritional quality parameters of tomato slices, including vitamin C content, lycopene concentration, total soluble solids, and moisture content. Fresh tomatoes sourced from the Dawanau market in Kano were sliced uniformly at five millimetres thickness and subjected to hot-air drying at 50, 60, 70, and 80 degrees Celsius in a laboratory-scale tray dryer. Nutritional analyses were conducted at each temperature level using standard AOAC methods, and colour change was evaluated using a chromameter. The drying kinetics were modelled using the Newton and Page thin-layer models. Results indicate that drying at 60 degrees Celsius preserved significantly higher vitamin C and lycopene contents compared to higher temperatures, while achieving acceptable moisture reduction within practical processing times. The study draws on recent literature concerning thermal degradation of bioactive compounds and the optimisation of dehydration processes for tropical vegetables. Findings suggest that temperature-controlled drying can meaningfully reduce post-harvest losses while maintaining nutritional integrity. The outcomes are intended to inform small-scale food processors, extension services, and tomato processing enterprises in the North West zone on optimal drying protocols for value addition. Keywords: tomato, drying temperature, nutritional quality, post-harvest, Kano