Secagem e reidratação de fatias de maçã

Abstract

The apple is known for its crunchy texture, sweet flavor, and juicy pulp. One way to reduce its perishability by increasing its shelf life is to dehydrate the product. Before use on their end, many dry products, either as industrial inputs or used by the consumer, are rehydrated. This work aimed to dry and rehydrate apple slices 1 cm thick. Fruit slices were dehydrated to equilibrium at temperatures 50 and 70ºC and weighed regularly. After drying at different temperatures, the apples were rehydrated to equilibrium at 2 °C (refrigerator temperature) and 25 °C (room temperature), being weighed periodically. The experimental data were adjusted to Fick's Law, allowing the calculation of the effective coefficient of water diffusion, and to twelve empirical/semi empirical models. The drying of the fruits resulted in foods with water activity sufficiently low to ensure their microbiological safety (< 0.6); while the rehydration of the dried samples was able to recover the moisture of the fresh fruits. The influence of temperature in the operations was verified, and higher rates were observed for the highest operating temperatures. Fick's law satisfactorily represented the experimental data of dehydration of apples (R² > 0.82, P > 10%, RMSE close to zero), but not their rehydration, since R² < 0.7. Wang and Sing’s model was the one that best represented the drying data at both temperatures. For apples dehydrated at 50 ºC, the Diffusion Approximation model was the one that best represented the experimental data of rehydration at 25 and 2 °C. For apples dehydrated at 70 ºC, Page's model best represented rehydration at 25 and 2°C.