Effect of various dipping pretreatment on drying kinetics of Thompson seedless grapes

The effect of various dipping pretreatments on drying kinetics of grapes under warm air convective drying conditions has been studied. A dryer was built to perform the experiment under controlled condition of drying air at temperature 60 degrees C and velocity 0.5 m/s. The various pretreatments of the grapes include treatment with commercial dipping oil, ethyl oleate, olive oil, and hot sodium hydroxide solution. Kinetic studies of the treated grapes for all the pretreatments were also made. The drying behaviour of the treated grapes was found to be in good agreement with Page's model, though drying constants of Page's model for each pretreatment were found to be different. Sensory evaluation was also carried out for all pretreatments. Dipping oil pretreatment experiments were also conducted at temperatures other than 60 degrees C to determine the dependence of Page's drying constant k on the drying air temperature (C) 1999 Elsevier Science Ltd. All rights reserved.