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Drying kinetics of Cape gooseberry was studied and modeled during processing at four temperatures (60, 70, 80 and 90C). Desorption isotherm was obtained at 40C giving a monolayer moisture content of 0.086 g water/g d.m. Experimental drying curves showed that drying process took place only in the falling rate period. Several thin‐layer drying models available in the literature were evaluated based on statistical tests as sum squared error (SSE), chi‐square (χ2) and determination coefficient (R2). Effective moisture diffusivity of Cape gooseberry was in the range of 4.67–14.9 × 10−10 m2/s. A value of 38.78 kJ/mol was determined as activation energy. When comparing the experimental with predicted moisture values, the Midilli–Kucuk model was found to give the best fit quality (SSE < 0.001, χ2 < 0.001, R2 > 0.99), showing this equation to predict very accurately the drying time of Cape gooseberry under the operating conditions studied. Practical Applications Demand for natural and healthy fruit and vegetable products with extended shelf life has urged the dehydrated food industry to look for raw materials of desirable nutritional and functional properties. Cape gooseberry, with its highly nutritional composition and its content of biologically active health‐promoting components, is therefore an excellent fruit raw material for the dehydrated food industry. Drying has the potential to deliver safe food products through enzyme inactivation and microbe destruction. Therefore, modeling of drying kinetics, as well as acquiring data on desorption isotherm or diffusion coefficient, is needed by the industry to manage efficiently dehydration techniques and avoid energy misuse. This could serve to demonstrate the environmental consciousness of the food processing industry, greatly appreciated by consumers.

The objective of this work was to study the influence of the drying temperature, infrared (IR) radiation assistance, and the Mylar™ film thickness during Physalis fruit purée drying by the Refractance Window™ (RW™) method. For this, a RW™ dryer layout with a regulated bath at working temperatures of 60, 75, and 90 • C, Mylar™ thicknesses of 0.19, 0.25, 0.30 mm and IR radiation of 250 W for assisting RW™ drying process was used. Experimental curves data were expressed in moisture ratio (MR) in order to obtain moisture effective diffusivities (non-assisted RW™: D eff = 2.7-10.1 × 10 −10 m 2 /s and IR-assisted RW™: D eff = 4.2-13.4 × 10 −10 m 2 /s) and further drying curves modeling (Page, Henderson-Pabis, Modified Henderson-Pabis, Two-Term, and Midilli-Kucuk models). The Midilli-Kucuk model obtained the best-fit quality on experimental curves regarding statistical tests applied (Coefficient of Determination (R 2 ), Chi-Square (χ 2 ) and Root Mean Square Error (RMSE). Microscopical observations were carried out to study the RW™ drying conditions effect on microstructural changes of Physalis fruit purée. The main findings of this work indicated that the use of IR-assisted RW™ drying effectively accelerates the drying process, which achieved a decrease drying time around 60%. Thus, this combined RW™ process is strongly influenced by the working temperature and IR-power applied, and slightly by Mylar™ thickness.Foods 2020, 9, 343 2 of 18 water. This plastic film having the property to be able to transfer heat by conduction and by radiation, allows the food material to dry at moderate temperatures achieving usually shorter drying times. The RW™ method is attractive to the heat-sensitive food industry due to the high quality of the products obtained, and that the equipment is relatively cheap (one-third compared to a freeze-dryer). It also has the advantage that the operational cost of a dryer by the RW™ method is approximately half that of a freeze-dryer [3].Traditional drying technologies, such as hot-air convective drying, vacuum drying, microwave drying, freeze-drying, among others, aim to ensure that the food quality and stability are preserved during the storage period, being, at the same time, as efficient as possible. However, so as to fulfill efficiently the drying process, shortening operation times and enhancing product quality, as well as using combined drying technologies in which different sources of energy are involved, are becoming more and more current. In this sense, there is the possibility of assisting the different drying processes with several forms of energy that accelerate transfer of matter from the diverse feed sources. Infrared (IR) radiation assistance could be seen as a convenient and alternative method to combine with RW TM drying process of high quality fruit pulps or purées. Hence, when food materials are subjected to an electromagnetic field, the wave penetrates directly into the material, resulting in fast volumetric heating. These electromagnetic waves in IR radiation are displayed unde...