EMPIRICAL MODELING OF DRYING PROCESS FOR APPLE (CV. GRANNY SMITH) SLICES AT DIFFERENT AIR TEMPERATURES

This study investigated and modeled the drying kinetics of Granny Smith variety apples at five different temperatures from 40 to 80C, with an air flow of 2.0 ± 0.1 m/s and load density of 4.4 kg/m2. Prior to mathematical modeling of the drying process, desorption isotherm was determined using the Guggenheim, Anderson and de Boer equation. Empirical equations used for modeling the drying kinetics were Newton, Henderson-Pabis, Page and Modified Page models. The fit quality obtained with each model was evaluated using statistical tests (determination coefficient, sum squared error, root mean square errors and chi-square). The kinetic parameters values were between 0.0046–0.0115/min for k1; 0.0050–0.0129/min for k2; 0.0006–0.0039/min for k3; and 0.0041–0.0090/min for k4. When comparing experimentally obtained values with those calculated from the models, it was shown that the best fit on the data was obtained employing the Modified Page model based on the statistical tests used for evaluation. PRACTICAL APPLICATION The main value of this study is the application of the proposed mathematical models using Newton, Henderson-Pabis, Page and Modified Page equations in food dehydration, which can be considered as a basis for an estimation of drying time in this kind of industry. The study of drying kinetics of apple cv. Granny Smith arouses technological and commercial interest, since this product is worldwide and extensively used in prepared foods including snack preparations, whole-grain breakfast foods and functional food among others. In addition, dried apples and other dried fruit exports (raisins and prunes) from Chile have become very important for the economy of the country, thanks to Free Trade Treaties. The major markets for these products include the U.S.A., the European community and Japan.

[1]  Gikuru Mwithiga,et al.  The drying kinetics of kale (Brassica oleracea) in a convective hot air dryer , 2005 .

[2]  P. Fito,et al.  Mathematical modeling of hot-air drying kinetics of red bell pepper (var. Lamuyo) , 2007 .

[3]  A. Bakshi,et al.  Finite Element Analysis of Moisture Diffusion in Stored Foods , 2006 .

[4]  Piotr P. Lewicki,et al.  The applicability of the GAB model to food water sorption isotherms , 1997 .

[5]  Antonio Vega,et al.  Modelado de la Cinética de Secado de la Papaya Chilena (Vasconcellea pubescens) , 2006 .

[6]  K. Saçılık,et al.  The thin layer drying characteristics of organic apple slices , 2006 .

[7]  E. Akpinar,et al.  Thin layer drying of red pepper , 2003 .

[8]  Mehmet Pala,et al.  The thin-layer drying characteristics of corn , 2003 .

[9]  Wijitha Senadeera,et al.  Influence of shapes of selected vegetable materials on drying kinetics during fluidized bed drying , 2003 .

[10]  W. Jomaa,et al.  Moisture diffusivity and drying kinetic equation of convective drying of grapes , 2002 .

[11]  Carmen Rosselló,et al.  Use of exponential, Page's and diffusional models to simulate the drying kinetics of kiwi fruit , 2004 .

[12]  S. Alzamora,et al.  Convective air drying of apples as affected by blanching and calcium impregnation , 2008 .

[13]  Xue-Wu Zhang,et al.  Desorption Isotherms of Some Vegetables , 1996 .

[14]  İbrahim Doymaz,et al.  Drying characteristics and kinetics of okra , 2005 .

[15]  H. Feng,et al.  Image analysis and dynamic modeling of thin-layer drying of osmotically dehydrated pumpkin , 2008 .

[16]  T. Labuza,et al.  Kinetic History Effect on Lipid Oxidation of Methyl Linoleate in a Model System , 2006 .

[17]  S. Babalis,et al.  Influence of the drying conditions on the drying constants and moisture diffusivity during the thin-layer drying of figs , 2004 .

[18]  Dursun Pehlivan,et al.  Modelling of drying kinetics of single apricot , 2003 .

[19]  E. Akpinar.  Determination of suitable thin layer drying curve model for some vegetables and fruits , 2006 .

[20]  Vaios T. Karathanos,et al.  Drying kinetics of some vegetables , 2003 .

[21]  V. Karathanos,et al.  Application of a Thin-Layer Equation to Drying Data of Fresh and Semi-dried Fruits , 1999 .

[22]  Darko Velić,et al.  Influence of airflow velocity on kinetics of convection apple drying , 2004 .