Drying kinetics of blueberry pulp and mass transfer parameters: effect of hot air and refractance window drying at different temperatures

Abstract

Blueberry pulp was dried using hot air (HA) and refractance window (RW) methods at 55–95 °C, the drying kinetics were described by the Page (k and n) and Fick (Deff1) Models. In addition, mass transfer parameters (drying coefficient (S), lag factor (G), Biot number (Bi), effective diffusivity (Deff2), external mass transfer (hm)); and the activation energy were analysed. As results, the Page model showed the best fit, Deff1 and k parameters increased with temperature, especially for RW drying at 95 °C. RW method reduced the HA drying time by more than 30%. Furthermore, the 0<Bi<0.4 values were related to variations in internal resistance with temperature, except for HA drying at 95 °C, where the external resistance was also reduced. In conclusion, mass transfer parameters suggested that internal resistance was more important during HA drying, while RW was the most effective method since it needed lower time to dry samples.