The mass migrations during osmotic dehydration of guava were studied. Parallelepiped shaped slices were dipping in syrup of distilled water and sucrose with two concentrations and two temperatures. It was supposed that a three-dimensional diffusion model with boundary condition of the first kind satisfactorily describes the mass migrations and that the volume and effective mass diffusivities can be assumed constant during the process. The effective mass diffusivities were determined by coupling the three-dimensional analytical solution of the diffusion equation with an optimizer based on the inverse method. The proposed model well described the kinetics of water and sucrose migrations and enabled determining the mass distributions (water and sucrose) within the product at any instant. 1. Introduction In order to prolong the shelf life of fruits, an alternative is the water removal from these agricultural products. In this sense, one of the methods of partial water removal is the osmotic dehydration. For fruits, generally dipping of pieces of the product in a solution of distilled water and sucrose is used, at given concentration and temperature. As examples, the following processes involving osmotic dehydration of fruits through dipping of the product in syrup can be cited: apples [1], mango [2], acerola [3], melon [4], papaya [5], banana [6], pumpkin, kiwi and pear [7], coconut [8], and pineapple [9]. According to Yadav and Singh [10], many advantages of water removal by the use of osmotic dehydration can be cited. Among them is (1) a low temperature water removal process and hence the minimum loss of color and flavor take place. (2) Flavor retention is more when sugar syrup is used as osmotic agent. (3) Energy consumption is less when no phase change is involved. (4) It increases solid density due to solid uptake and helps in getting better quality product in freeze drying. (5) The textural quality of product is better after reconstitution. (6) The storage life of product is greatly enhanced. (7) Simple equipment is required for the process. In order to extract the major quantity of information on the osmotic dehydration process of a fruit, generally a mathematical model is used to describe the water removal and sucrose uptake. Although empirical models are used to describe osmotic dehydration [4, 6, 7], the most frequent in the literature is diffusion model [1–3, 8, 9, 11]. According to Da Silva et al. [9], the main advantage of diffusion models is the possibility to predict the distributions of mass content (water and sucrose) within the product at
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