Air-drying of fresh and osmotically pre-treated pineapple slices: Fixed air temperature versus fixed slice temperature drying kinetics

In this investigation, the air drying characteristics of fresh and osmotica lly pre-treated pineapple slices in a tray dryer were studied under differe nt operating conditions. The air velocity varied from 1.5 to 2.5 m/s and th e air temperature from 40 to 70 degreesC. The analytical solution of the se cond Fick's law for an infinite slab was used to calculate effective diffus ion coefficients and their temperature dependence could be well represented by an Arrhenius-type equation. Comparison of the results showed that the d iffusion coefficients were lower for the pre-treated fruit. By means of aut omatic control, it was possible to obtain drying curves under conditions of constant product temperature, which showed to be an alternative to reduce the drying time of pineapple slices.