Empirical model for describing continuous and intermittent drying kinetics of apple pieces

The present study aimed to assess continuous and intermittent drying of apple pieces, proposing a modified Page model to describe the kinetics of these processes. Drying was conducted in a forced air circulation oven at temperatures of 50 and 70 °C. For intermittent drying, the intermittency ratio was 2/3 and the tempering periods were 30, 60 and 120 min. The proposed model described well all drying kinetic processes. For a given temperature, the comparison between the effective times of intermittent drying and continuous drying indicated that intermittency leads to saving for all tempering periods, reaching up to 45%. It was observed that, even for a single intermittency ratio, 2/3, the tempering period influenced the saving of effective drying time and, therefore, the saving of energy. Highest saving occurred for tempering period of 30 min, whereas the worst result occurred for 120 min.