Shrinkage empirical modeling during drying of grapes pretreated with ultrasound and carboxymethyl cellulose

High temperatures during drying, with loss of water in the meantime, cause tension in the food, change the microstructure and reduce the volume (shrinkage). In this study, the effect of ultrasonic pretreatment at 10, 20 and 30 minutes and carboxymethyl cellulose with concentrations of 0.1, 0.2 and 0.3 percent on grapes shrinkage during drying and its modeling was examined. In this study, pretreated grapes were dried in a tunnel dryer and their volumetric changes were measured. Results showed that all the pretreatments have higher shrinkage compared with control samples, but this difference was not statistically significant. Also, by increasing ultrasound time, the shrinkage of the samples increased compared with control treatment. Control and pretreated samples with ultrasound for 30 minutes had the lowest and highest rate of shrinkage, respectively, in the various studied treatments. In the samples pretreated with both ultrasound and CMC, it was observed that by increasing the concentration of CMC, shrinkage of the samples decreases compared to its lower concentrations.