The choice of the drying process plays a key role in reducing the costs of electricity consumption in the food industry. Thus, this study aimed to evaluate continuous and intermittent drying of rough rice, using empirical and diffusion models to describe the drying kinetics, considering only effective time of operation to compare and evaluate these processes. Experiments were carried out during the month of April 2018, in Campina Grande, Paraiba Brazil, and were conducted with continuous and intermittent drying of rough rice grains (about 20 g, each experiment) using a fixed-bed dryer with constant power, at temperatures of 50 and 70 °C. For the intermittent experiments, the intermittency ratio was α = 2/3 and the drying periods were 10 and 20 min, with intermittency periods of 20 and 40 min, respectively. Comparison between continuous and intermittent drying kinetics indicated reduction in the effective time of all intermittent drying experiments, reaching up to 32.2%, hence promoting energy saving. It was also found that a one-dimensional diffusion model with boundary condition of the first kind properly described all rough rice drying processes and that the effective mass diffusivity is higher in intermittent drying, compared to continuous drying at the same temperature.

The use of waste has been the focus of attention of the agri-food sector, and a fruit with large amount of waste is the passion fruit. Its peel consists of albedo and flavedo, which can be used to manufacture flour, and some studies propose the need to remove the flavedo as well as to perform maceration. The objective of the present work was to study the drying process to produce flour from passion fruit albedo and whole peel, checking the influences of the flavedo removal and maceration steps, as well as the drying temperatures (70 and 80 ºC). Yield after drying was calculated and it was shown to be low. Page, Silva et alii, Henderson and Pabis and Logarithmic mathematical models were fitted to the experimental data using LAB Fit software. The statistical indicators used to identify the best fit were coefficient of determination (R2) and chi-square (χ2). The Page model was the one that fitted best to the data, showing the best statistical indicators. Also, it can also be highlighted that the sample composed of peel without maceration and dried at 70 ºC had the best results regarding the statistical indicators.

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One approach to improve sustainable agro-industrial fruit production is to add value to the waste generated in pulp extraction. The processing of cumbeba (Tacinga inamoena) fruits generates a significant amount of waste, which is discarded without further application but can be a source of bioactive compounds, among other nutrients. Among the simplest and most inexpensive forms of processing, convective drying appears as the first option for the commercial utilization of fruit derivatives, but it is essential to understand the properties of mass transfer for the appropriate choice of drying conditions. In this study, cumbeba waste was dried at four temperatures (50, 60, 70 and 80 °C). Three diffusion models were fitted to the experimental data of the different drying conditions. Two boundary conditions on the sample surface were considered: equilibrium condition and convective condition. The simulations were performed simultaneously with the estimation of effective mass diffusivity coefficients (Def) and convective mass transfer coefficients (h). The validation of the models was verified by the agreement between the theoretical prediction (simulation) and the experimental results. The results showed that, for the best model, the effective mass diffusivities were 2.9285 × 10−9, 4.1695 × 10−9, 8.1395 × 10−9 and 1.2754 × 10−8 m2/s, while the convective mass transfer coefficients were 6.4362 × 10−7, 8.7273 × 10−7, 8.9445 × 10−7 and 1.0912 × 10−6 m/s. The coefficients of determination were greater than 0.995 and the chi-squares were lower than 2.2826 × 10−2 for all simulations of the experiments.