Comparative study of Solar tunnel and Indirect hybrid solar cabinet dryers on drying kinetics and quality of tree tomato (Solanum betaceum Cav.) powder

Harnessing solar energy to transform food manufacturing process can reduce dependance on fossil fuels, which are costly and generate greenhouse gas emissions. The study evaluated the impact of indirect hybrid solar cabinet dryer (IHSCD) and solar tunnel (ST) dryer on the drying kinetics and quality characteristics of tree tomato powder. For both dryers, the Modified Page Model was the best among the models tested. The values of k and n for the IHSCD were 0.116 and 8.128 respectively while for the ST they were 0.146 and 4.022 respectively. There was no difference in the L*, a*, b*, C* and ΔE color values (p > 0.05) while the h* color value of the fruit powder was higher for the ST (30.33) than for the IHSCD (25.63) dryer. Significant difference (p < 0.001) was recorded on the water solubility % at 50 °C with higher value °f 98.53 for the ST dryer and 97.68 for the IHSCD dryer. There was no significant difference in the rehydration ratio, hygroscopicity and water solubility (at 25 °C and at 80 °C) (p > 0.05). Flavonoids were higher (4.18 mg CE/100 g) in the ST than in the IHSCD which recorded a value of 3.96. The IHSCD yielded higher values of Vitamins A (RAE) of 48.77, and Vitamins C (mg/100 g) of 348.89 than the ST dryer (45.48, 338.02 respectively). Considering the physical and technological properties, the differences between the two drying processes were actually not significant but taking into account the retention of the functional attributes, the IHSCD would be the superlative choice. Application of IHSCD can act as a game changer to smallholder farmers in the tropics, in transforming tree tomato from subsistence farming, into value added, nutritious, safe, and shelf-stable food product.