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In the modern world, light and healthy meals are increasingly consumed between the main meal courses. Therefore, market has made a wide variety of products of this type available, usually without artificial additives. This study aimed to produce snacks through the thin-layer drying of kiwi slices. Circular kiwi slices were cut into various thicknesses (5.0, 10.0 and 15.0 mm) and subject to different drying air temperatures (50, 60, 70 and 80 o C). Drying was described using several mathematical models, both diffusion (boundary condition of the third kind) and empirical (Henderson-Pabis, Lewis, Page, Silva et al.) models. According to diffusion model, kiwi slices showed an almost uniform moisture distribution over time. The Page equation/model showed the best fit to the experimental data, compared to other models. At the end of the drying process (until equilibrium), slices with initial thickness of 5.0 mm had a rigid consistency, suitable for production of flour through grinding. On the other hand, slices with initial thicknesses of 10.0 and 15.0 mm were soft; thus, they can be consumed as snacks. Sensory and physicochemical analyses showed that the product cut with initial thickness of 15.0 mm and dried at temperature of 70 ºC (until moisture content of 0.31 kg water /kg dry matter ) was the tastiest one and showed good results for the analyzed chemical compounds.

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In this article, a two-dimensional model is proposed to determine thermal diffusivity and convective heat transfer coefficient, providing the average values, their uncertainties and the covariance matrix referring to these parameters for a product with cylindrical geometry during its cooling. The proposed model used a two-dimensional numerical solution of the diffusion equation for the direct problem; an experimental dataset referring to the cooling kinetics in the center of the product and an optimizer program based on the Levenberg-Marquardt algorithm for the inverse problem. The model was used with success to determine the thermal properties, their uncertainties and the covariance matrix of a cucumber during its cooling. The obtained results allowed establishing a confidence band that made it possible to graphically evaluate the precision of a new simulation for a cucumber with different dimensions.

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