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 (D_eff) increased as high as the temperature of the heating medium. The variation of D_eff of swirling flow was ranging from 6.72?×?10^?9 to 10.23?×?10^?9 m²/s, while the variation of D_eff 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.