A Study of the Diffusivity Coefficient Changes and Shrinkage of Dates (Barhi in Khalal Stage) During Drying through a Cabinet Dryer

Date palm (Phoenix dactylifera L.) is an important agricultural crop in Iran. To extend the shelf life of date palm fruit, some methods of preservation are employed, including drying. Drying influences physicochemical and quality characteristics of products, thus modeling of drying kinetics is a tool for process and therefore quality control. In this research Barhi dates at khalal stage of maturity, with and without peel, were dried in a laboratory scale hot-air dryer, under air flow of 1.5 m/s and air temperatures of 60, 70 and 80? C. The experimental shrinkage data showed a linear relationship with moisture content, a reduction in sample volume, and decrease in moisture content. The effect of temperature and the fruit being peeled or not on the shrinkage phenomenon can thus be neglected. A determination of water diffusivity could help in drying simulation for predicting the suitable drying conditions (air temperature and drying durations).Water diffusion coefficient values were assessed. The determined effective water diffusivity values ranged from 1.94×10-9 to 1.18×10-8 m2/s. The results revealed that the effective diffusion coefficient increased with increasing temperature. The results also showed that temperature and the fruit being peeled or not, have dominating effects on effective diffusion coefficient. The evolution of effective water diffusivity coefficient was described as a function of temperature through Arrhenios relation. The experimental diffusivity values were in a good agreement with the predicted values obtained from Arrhenios relation.