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Viseu, Portugal

Guine R.P.F.,Polytechnic Institute of Viseu | Henrriques F.,Quinta da Alagoa | Barroca M.J.,Polytechnic Institute of Coimbra
Food and Bioprocess Technology | Year: 2012

The aim of this work was to determine the mass transfer properties of pumpkin (Cucurbita moschata) exposed to air drying. The drying temperatures tested ranged between 30°C and 70°C, and the kinetic behavior was studied in this temperature band. The samples were analyzed in terms of moisture content, acidity, proteins, lipids, and crude fiber, both in the fresh state and after drying. From the chemical analyses made, it was possible to conclude that drying induces some reductions in acidity, lipids, fibers, and proteins. As to the influence of the drying temperature on the process, it was observed that a temperature rise from 30°C to 70°C led to a 70% saving in drying time. The results obtained by fitting the experimental data to the kinetic models tested allowed concluding that the best model for the present case is Henderson-Pabis, and the worst is Vega-Lemus. Furthermore, in this work, it was possible to determine the values of the diffusion coefficient at an infinite temperature, D e 0, and activation energy for moisture diffusion, E d, which were, respectively, 0. 0039 m 2/s and 32. 26 kJ/mol. Similarly, the values of the Arrhenius constant and the activation energy for convective mass transfer, respectively, h m 0 and E c, were also calculated, the first being 3. 798 × 10 8 m/s and the latter 86. 25 kJ/mol. These results indicate that the activation energy for convective mass transfer is higher than that for mass diffusion. © 2009 Springer Science + Business Media, LLC. Source

Guine R.P.F.,Quinta da Alagoa | Guine R.P.F.,Polytechnic Institute of Viseu | Almeida I.C.,Quinta da Alagoa | Correia A.C.,Quinta da Alagoa | And 2 more authors.
Journal of Food Measurement and Characterization | Year: 2015

The main objective of the present work was to dry grapes of Crimson variety through different methodologies in order to find an alternative for the production of raisins. Different methodologies were used for drying: solar direct exposition in a greenhouse and in convective drying chambers with constant air flow at two temperatures: 50 and 60 °C. Some chemical analyses were made, namely for total sugars, acidity, total phenols, total anthocyanins and total tannins. Also some physical properties were evaluated, specifically color and texture. A sensorial analysis of the dried products was undertaken to evaluate the acceptability by consumers. The raisins produced by the different methodologies didn’t show significant differences at the chemical and physical levels. However, it was observed that the dried samples contained higher amounts of total phenolic compounds, anthocyanins and tannins in comparison to the fresh grapes. Sensory evaluation result showed that dried grapes produced using different methodologies was similar to commercial raisins. © 2015, Springer Science+Business Media New York. Source

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