Shoughy, M., Abd El-Galeel, M. (2008). DRYING TECNOLOGY OF ROSELLE UNDER VACUUM. Journal of Soil Sciences and Agricultural Engineering, 33(5), 3457-3468. doi: 10.21608/jssae.2008.203078
M. I. Shoughy; M. A. Abd El-Galeel. "DRYING TECNOLOGY OF ROSELLE UNDER VACUUM". Journal of Soil Sciences and Agricultural Engineering, 33, 5, 2008, 3457-3468. doi: 10.21608/jssae.2008.203078
Shoughy, M., Abd El-Galeel, M. (2008). 'DRYING TECNOLOGY OF ROSELLE UNDER VACUUM', Journal of Soil Sciences and Agricultural Engineering, 33(5), pp. 3457-3468. doi: 10.21608/jssae.2008.203078
Shoughy, M., Abd El-Galeel, M. DRYING TECNOLOGY OF ROSELLE UNDER VACUUM. Journal of Soil Sciences and Agricultural Engineering, 2008; 33(5): 3457-3468. doi: 10.21608/jssae.2008.203078
2Food Tech. Department, Fac. of Agric., Kafr El-Sheikh Univ.
Abstract
The characteristics for vacuum drying of roselle at three pressure levels (normal atmospheric pressure, two vacuum levels at -125 and -250 mbar), three drying temperatures (30, 40 and 50oC) and the effectiveness of tempering periods in drying cycle were studied. The drying coefficients, drying characteristics and energy consumption as well as the product quality after drying were evaluated. Mathematical models describing the change of drying characteristics of roselle as dependent variables with vacuum level and drying temperature as independent variable were also evaluated. The drying process continued until the calyces of roselle moisture content decreased from 67.5 %, (wet basis) to the mass of each sample remained almost constant. The results revealed that, vacuum level and drying temperature were very effective in removing moisture from fresh roselle calyces. Increasing rates of moisture removal and reduced energy consumption for drying were readily achieved with decreasing vacuum levels and increasing drying temperatures for about 2.4 times the rate currently achieved in atmospheric pressure drying. The developed mathematical models were highly accurate and can be used to describe the drying conditions of roselle in the commercial scale. Short vacuum drying and tempering cycles are more effective in removing moisture than long ones. The quality of dried product achieved through vacuum drying was higher than that currently being experienced in normal atmospheric pressure drying process.
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