Drying Characteristics of Apple Slabs after Pretreatment with Supercritical CO 2

AbstractSupercritical CO 2 pretreatment before dehydration leads to a faster dehydration rate. The best supercritical CO 2 pretreatment conditions for the most effective dehydration were 45 o C, 25 MPa and 55 o C, 25 MPa. Increasing pressure of the supercritical CO 2 pretreatment system tended to accelerate the dehydration rate more than increas-ing temperature did. Samples pretreated at higher temperatures and pressures showed greater shrinking and pore distribution on scanning electron microscopy. Control samples maintained their cell walls, whereas samples pre-treated at higher temperatures and pressures showed more cell disruption, and more pores were observed. Pore sizes of control and pretreated samples were about 100 and 70～80 μm, respectively. Samples pretreated at higher temperatures and pressures had smaller pores and a denser distribution. Key words: dehydration, pretreatment, rehydration, supercritical carbon dioxide   