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

Abstract

ABSTRACT 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.