Effects of different pre-treatments on energy consumption during freeze drying of pineapple pieces
Osmotic dehydration and microwave heating were combined with freeze-drying to obtain dehydrated pineapple. The effects of combined technologies on energy consumption, drying time and kinetics were analyzed. It was generally observed that the processes that include osmotic dehydration reduced the sublimation kinetics, but showed low consumption of energy during the whole dehydration process. A positive synergistic effect on mass transfer is observed when microwaves are additionally applied before osmotic dehydration and freeze-drying, due to solid gain after osmotic pretreatments; energy utilization throughout the complete dehydration processes can be reduced up to 61.3% when measured as kJ/kg of obtained product.