Effect of Shape of a Fruit Model-Product (Sodium Alginate Gel) Dryed by Microwave and Modeling of Drying Kinetics

Abstract

Model-products are products designed to imitate and understand the heat treatment behavior of real products. This is the case of a sodium alginate gel used to simulate the drying behavior of water-rich fruit products (e.g. tomatoes). The aim of this study was to investigate the effect of the shape of a sodium alginate gel as a model-product of microwave drying. Then, from this shape of the gel, find a semi-empirical model that simulated well its drying kinetics. Thus, a sodium alginate gel was developed in cylindrical and slab shapes, which had almost identical volumes and weights, to assess the influence of product shape on drying kinetics. Experiments were performed in a stereo-mode cavity at 2450 MHz with output microwave powers densities of 1, 1.5, and 2 W / g. A regular weighing of dried product mass was carried out to better appreciate drying behavior. In addition, the temperature at the product core was measured by an optical fiber to observe the evolution of gel temperature. The experiments showed that the cylindrical shape of the model-product dries faster than the slab shape. Moreover, the Midilli mathematical model best fit the drying kinetics of the cylindrical shape of the gel.