effect of osmotic and ultrasound pretreatments on some quality characteristics of air-dried banana

banana is one of the most important tropical fruit from commercial and industrial point of view. this fruit is an extremely perishable fruit which can not be preserved using freezing process. therefore, drying is the most promising method. conventional air drying is energy intensive and consequently expensive method. pre-treatments can be used to reduce the initial water content or to modify the fruit tissue which will result in higher yield with lower costs. in this research, the effect of osmotic dehydration and ultrasonic pre-treatment variables prior to air drying of bananas, including the type of solution (glucose, sucrose), time of immersion in osmotic solution (30, 45, 60 min), solution concentration (brix 30 and 50), ultrasonication time (10, 20, 30 min) on water loss, solid gain, shrinkage, effective diffusivities and color in the process were studied. results showed that the highest rate of water loss and solid gain and also the lowest rate of shrinkage were obtained in both pre-treatments when 50% glucose concentration was applied. the results indicated that unlike ultrasonication, osmotic pretreatment had a significant effect on color parameters of dried bananas.