Study on kinetics of flow characteristics in hot air drying of pineapple.

The aim was to evaluate the kinetic parameters, total color differences (∆E*) and browning index differences (∆BI) of air flow pineapple drying. The experiments were performed on air temperatures at 60 and 70 °C, and air velocities at 1.5 and 2.0 m/s. The kinetic parameter (k) increased when air temperature was increased for all air velocity. The effective diffusivity coefficient (Deff) increased as high as the temperature of the heating medium. The variation of Deff of swirling flow was ranging from 6.72 × 10-9 to 10.23 × 10-9 m2/s, while the variation of Deff of non-swirling flow was ranging from 6.40 × 10-9 to 9.42 × 10-9 m2/s. The drying time of swirling flow was shorter than non-swirling flow in each drying condition. Moreover, the ∆E* and ∆BI of pineapple in swirling flow were lower than that obtained from non-swirling flow. Therefore, the convective drying using swirling flow can be minimized for drying time and color deterioration.