Thin Layer Drying of Hayani Date Using a Portable Dryer

Abstract

A study was carried out to test and evaluate a portable mechanical date dryer using butanegas as heat energy source. The temperature of drying air was adjusted to be approximately constant during the experiment of period at 40 , 50 , 60 and 70C and air velocity of 1 ,1.5 and 2 m/s. Two empirical models (Exponential and Page) were examined to describe the drying behaviour of date. The change in date moisture content during the drying process, thermal efficiency of the drying process and the total and reducing sugars of the dried date were also determined. The obtained results showed that, both of the examined models could satisfactory describe the change in date moisture content during the drying process. While the Page's model could predict the change in moisture content of date more adequately than the simple model. The dryer thermal efficiency increased with the increase of drying air temperature and air velocity, and it ranged from 32.23 to 69.84 % for the unpeeled date, from 33.82 to 71.63% for the un-peeled treated date and from 35.42 to 75.13% for the peeled date. Also, the total and reducing sugars percentages decreased with the decrease of drying air temperature and air velocity and the reducing sugar ranged from 44.85 to 51.38 % while the total soluble sugar ranged from 55.95 to 65.14 % .