Drying characteristics of mango slices using the Refractance Window™ technique

Mango slices (1 and 2 mm thickness) were dried by using the Refractance Window™ (RW) technique with the water bath temperature set at 92 °C. Drying kinetics, water activity, and color change were determined and compared with those obtained by drying the slices in a tray dryer at 62 °C and an air velocity of 0.52 m/s. At 1 h, moisture contents of 0.013 (for 1 mm sample) and 0.048 (for 2 mm sample) kg water/kg dry solid for RW, and 0.966 (for 1 mm sample) and 3.614 (for 2 mm sample) kg water/kg dry solid for tray drying were obtained and water activity was less than 0.5 for RW and close to 0.97 for tray drying. The tray dryer took 4 h to reach results similar to those of RW at 1 h. The samples dried by RW exhibited diffusivities of 4.40 × 10⁻¹⁰ (for 1 mm sample) and 1.56 × 10⁻⁹ (for 2 mm sample) m²/s, which are larger than those exhibited by the air-dried samples, 2.08 × 10⁻¹¹ (for 1 mm sample) and 6.83 × 10⁻¹¹ (for 2 mm sample) m²/s.