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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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Lima bean is a legume produced and consumed in various countries. To reduce post harvest losses and to enable the storage for long periods, an alternative is to dry the product. To describe the drying process, a mathematical model is usually required. In this article, four empirical equations available in the literature were used to simulate thin layer drying kinetics of lima bean at temperatures of 40, 50 and 60°C. The four empirical equations were chosen based on their simplicity, involving only one or two fitting parameters. The statistical indicators showed that the Page and Silva et al. models were the best ones to describe the process. These two empirical equations has helped to deduce an analytical expression for the drying rate and these expressions produce results which can be considered equivalent.

For the preservation of products obtained by dehydration, it is necessary to evaluate their physicochemical characteristics during storage. It was proposed, in the present study, to evaluate the stability of the kiwi cv. ‘Hayward’ powder, obtained at temperatures of 60 and 70 °C during its storage in laminated packages under controlled conditions of temperature (25 ºC) and relative humidity (75%) for 90 days. The parameter’s evaluated were: moisture content, ashes, soluble solids, titratable acidity (% citric acid), pH, water activity at 25 ºC, color for the parameters lightness (L*) and chromaticity (+a* red; -a* green; +b* yellow; and -b* blue), phenolic compounds, flavonoids, total chlorophyll and carotenoids. It was observed that, after the 90 days, for the powder obtained at 70 °C, the soluble solids and pH values were altered by the storage, which did not occur for the powder obtained at 60 °C. For both powders, the content of ash and bioactive compounds were not affected by storage. The parameter of lightness decreased in both powders. The powder obtained at 70 ºC proved to be better, showing lower content of moisture and total water activity, as well as the highest values of bioactive compounds.