Development of Physical Properties of Apple during Dehydration

  • Rym Mbarek Higher School of Food Industries of Tunis, 58 Av. Alain Savary, 1003 Tunis El Khadra City, Tunisia; Laboratory of Wind Energy Management and Waste Energy Recovery, Research and Technology Center of Energy (CRTEn), B.P. No. 95, Hammam-Lif 2050, Tunisia
  • Daoued Mihoubi Laboratory of Wind Energy Management and Waste Energy Recovery, Research and Technology Center of Energy (CRTEn), B.P. No. 95, Hammam-Lif 2050, Tunisia

Abstract

The evolution of physical properties (shrinkage, density and porosity) of cylindrical shaped apple samples (Golden Delicious) during convective drying was investigated. For this purpose, the weight and the dimensions (diameter, height) of apple samples were monitoring at regular time intervals of the drying process. A constant drying rate period was not detected although considering the reduction of the exchange surface area. Apple exhibited a clear anisotropy behavior of the shrinkage coefficients. The volume shrinkage of apple samples showed a linear relationship with moisture content (R2 = 0.996). A theoretical relation between the surface ratio and the volume ratio was determined (R2 = 0.956). During drying process, the apparent density of apples decreased with decrease in moisture content following a second-degree polynomial curve (R2 = 0.991), whereas the true density aggrandized with removal of water. The porosity of apple samples was showed to increase as drying progressed. At the starting of the drying process, the porosity changes resulted from the reduction of the total volume. Then, the porosity changes during drying were found to be a consequence of a loss of water and a simultaneous reduction of gaseous volume.

Keywords: apple, drying, shrinkage, density, porosity
Published online
2019-04-16
How to Cite
Mbarek, R. and Mihoubi, D. (2019) “Development of Physical Properties of Apple during Dehydration”, Periodica Polytechnica Chemical Engineering, 63(4), pp. 591-599. doi: https://doi.org/10.3311/PPch.13033.
Section
Articles