Desidratação osmótica e secagem convectiva da casca do melão (Cucumis melo l.): modelagem matemática e caracterização físico- química das farinhas obtidas.

Abstract

The present work aimed to study the melon peel convective drying under temperatures of 60 and 70ºC, with and without the osmotic dehydration pre-treatment for both drying conditions, as well as to perform the physical-chemical characterization of the flours obtained. The osmotic dehydration procedure was carried out at room temperature for a predetermined period of 35 hours, using a solution containing sucrose in a concentration of 20ºBrix. The drying, in turn, was carried out in an oven with forced air circulation, at the temperatures already mentioned, for the samples osmotically dehydrated and without pre-treatment. For the description of drying kinetics, empirical models were used, a diffusion model, considering shrinkage and variable mass diffusivity. The numerical solution of the one-dimensional diffusion equation, in Cartesian coordinates, was obtained through the finite volume method, with a totally implicit formulation, with a third type boundary condition. To choose the mathematical model that most satisfactorily described the drying kinetics of the melon skins, the parameters of Coefficient of Determination and Chi-square were considered, in addition to the adjustment of the curves through the graphical representations. After the drying procedure for the four experimental conditions, four flour formulations were elaborated, which were subsequently characterized through physical-chemical analyzes of moisture, ash, water and lipid activity. According to the results obtained, it was possible to verify that osmotic dehydration provided an increase in the gain of solids to the product, as well as a reduction in the initial moisture content and thickness, in addition to an increase in the equilibrium moisture content. Among the empirical models, Page's was chosen as the most reliable to describe the process. The diffusive model, in turn, presented the best results for the evaluated parameters, being even superior to the empirical ones, therefore, it was considered the most satisfactory. As for the results of the effective mass diffusivity and the convective mass transfer coefficient, it was noticed that the increase in the respective values was in line with the increase in the drying temperature. Regarding the physical-chemical characterization of the flours, only the moisture content of the samples that were not subjected to the osmotic dehydration pre-treatment was adequate, according to the current standard. As for ash analysis, samples that were not pre-dehydrated had the highest levels. With regard to water activity, all samples showed adequate results, since they were less than 0.6%. In the analysis of lipids, as expected, discrete results were obtained. Keywords: Empirical models; Diffusive models; Numerical solution; Cucumis melo L.; Food Technology.