Abstract: Osmotic dehydration is a pre-treatment for drying of fruits and vegetables, which can reduce the drying time and improve food quality. The effects of different osmotic pretreatments on apple hot-air drying behavior and physical characteristics of instant controlled pressure drop dried apple chips were investigated. Samples were immersed in monosaccharide (fructose, glucose), disaccharide (sucrose, maltose), trisaccharide (raffinose), and tetrasaccharide (stachyose), respectively. Sugar gain and water loss were analyzed. The samples were further hot air-dried and the experimental data were fitted successfully using the Page model. Compared with the untreated samples, osmotic dehydration using selected sugar solutions contributed to better texture and color retention. Samples pretreated by raffinose and stachyose immersion exhibited the highest crispness. This study could provide a reference for the choice of osmotic solutions for pretreatment prior to drying of fruits and vegetables.

Key words: apple, osmotic dehydration, drying behavior, quality