Drying Kinetics, Diffusivity, and Activation Energy for Hot Air Drying Of Different Shapes of Hayani Dates

One of the earliest techniques for preserving fruits is the drying process. Date palm fruit's with high fiber content, phenolic components, sugar, vitamins, and minerals make it a vital diet for human nutrition. The influence of shape (khalal halves, khalal pieces and rotab halves) and drying temperature ranged from 50 –70 oC on the drying kinetics of Hayani date palm fruits were studied. A constant air flow rate of 0.087 m3s-1 was used. The activation energy (Ea) and effective moisture diffusivity (Deff) were computed. Nine different thin-layer drying models were examined for describing the drying curves. The quality of date was assessed by estimating total and reducing soluble sugars content. The results showed that the drying process of dates took place during the falling rate period at all levels of air temperature. The average values of Deff varied from 4.733 x 10-10 to 1.044 x 10-9 for khalal halves, 6.419 x10-10 to 9.5971 x 10-10 for khalal pieces and 7.3275 x 10-10 to 1.1607 x 10-9 m2/s for rotab halves, respectively and Ea values were 35.1366, 15.6303 and 19.7316 kJ/mole for khalal halves, khalal pieces and rotab halves, respectively. The statistical analysis of fit tests revealed that Diamante et al. model proved a satisfactory fit for the experimental data for khalal halves while the mod. Henderson and Pabis model describe satisfactory data of khalal pieces and rotab halves. Total and reducing sugars increased with the increase of the drying air temperature for all date shapes.