Drying cut fruits with recirculated air for energy savings

The main focus of this study was to test the feasibility of saving energy while drying fruit by recirculating drying air at a constant rate. Four recirculation rates (0, 25, 50, and 75%) were used to dry peaches and apples. For these treatments, the amount of energy consumed, the moisture removed, and the total drying times were measured. Three quantitative parameters (color, shelf-life, and sugar content) were used to determine the final quality of the dried fruit.

For both fruits tested, total energy consumption showed very significant differences among recirculation rates (with 75% recirculation requiring the least energy). The 75% recirculation rate produced an energy savings over no recirculation of approximately 53% for drying peaches and 46% for drying apples. The total processing times, however, were nearly the same for all recirculation rates. In general, no substantial losses occurred in the product quality for fruits subjected to the higher recirculation rates as compared to those subjected to no recirculation. The results of this experiment helped to decide an optimal fixed recirculation rate for maximizing the energy savings without causing destruction in the product quality. By optimizing the energy saved, fruit dehydrators may be improved to produce dried fruits at a lower cost.