Polytechnic Institute of Viseu

Viseu, Portugal

The Polytechnic Institute of Viseu was created on 26 December 1979, through the Governmental Act-of-Law nº513-T/7. It is part of polytechnic higher education in Portugal.The Polytechnic Institute of Viseu is made up of six units:School of AgricultureSchool of EducationSchool of NursingSchool of TechnologySchool of Technology and Management Welfare ServicesThe institution has 7000 students and 400 teachers. Wikipedia.

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Mesquita J.R.,University of Porto | Mesquita J.R.,Polytechnic Institute of Viseu | Barclay L.,Centers for Disease Control and Prevention | Nascimento M.S.J.,University of Porto | Vinje J.,Centers for Disease Control and Prevention
Emerging Infectious Diseases | Year: 2010

To identify the prevalence and genetic variability of noroviruses in dogs, we tested fecal samples by using reverse transcription-PCR. We found canine norovirus in 40% and 9% of dogs with and without diarrhea, respectively. The virus was genetically unrelated to other noroviruses and constitutes a tentative new genogroup.

Correia P.,Polytechnic Institute of Viseu | Beirao-Da-Costa M.L.,University of Lisbon
Food and Bioproducts Processing | Year: 2012

The use of starchy flours in food systems greatly depends on the related functional properties of starch. The effect of drying temperatures on starch-related functional properties of flours obtained from fruits of the two most common Portuguese Castanea sativa varieties (Martainha and Longal) was evaluated. Flours were analysed for amylose and resistant starch contents, swelling ability, pasting properties and thermal characteristics. Drying temperature is positively correlated with amylose content, resistant starch and viscoamylographic properties, mainly the temperatures higher than 40 °C. Amylograms of fruits dried at 60 °C displayed higher peak viscosity (1370 B.U. and 2260 B.U. respectively for Longal and Martainha) when compared to the other temperatures tested (40 °C, 50 °C and 70 °C). Decreases in transition temperatures and in enthalpy evaluated by thermal analysis were observed with increasing drying temperatures, suggesting modifications in starch structure during the drying process. The effects of drying temperatures were more evident in Longal variety. The flours from the two chestnut varieties and from fruits dried at low temperatures and fruits dried at high temperature showed significant differences between the evaluated properties. © 2011 The Institution of Chemical Engineers.

Correia P.,Polytechnic Institute of Viseu | Cruz-Lopes L.,Polytechnic Institute of Viseu | Beirao-da-Costa L.,University of Lisbon
Food Hydrocolloids | Year: 2012

The structure and morphology of starch from fruits of two chestnut (Castanea sativa Mill.) varieties, Martainha and Longal, isolated by alkaline (A3S) and enzymatic (ENZ) methods were assessed. Chestnut starch granules were found to be round and oval in shape, consisting of medium/small granules, with a mean granule size ranging between 9 and 13μm. Isolated chestnut starch appeared to the naked eye as a white powder, with high values of L *, and the Longal variety produce starches duller than Martainha. No differences between samples were observed by FTIR analysis. The X-ray patterns of isolated starches are of C-type (more specifically of C b type) with a relative crystallinity between 31.5% and 39.8%. The 13C CP/MAS NMR spectra are similar for both varieties but different for the used isolation methods. The amorphous phase in the starch granules isolated by A3S methods was lower than that of the starch extracted by the ENZ method, making the B-type allomorph in the C-type starch granules more evident than in the A-type. Those differences in the structure of isolated starches are shown by a lower degree of damage, and a higher level of crystallinity of starches isolated by the A3S method, which means that its original structure is less affected or partially destroyed. This study would be helpful to better understand the relationships among structure and functional properties for a eventual industrial application of chestnut starches. © 2012 Elsevier Ltd.

Bastos N.R.O.,Polytechnic Institute of Viseu | Ferreira R.A.C.,Lusophone University of Humanities and Technologies | Torres D.F.M.,University of Aveiro
Signal Processing | Year: 2011

We introduce a discrete-time fractional calculus of variations on the time scale (hℤ)a,a∈ℝ,h>0. First and second order necessary optimality conditions are established. Examples illustrating the use of the new Euler-Lagrange and Legendre type conditions are given. They show that solutions to the considered fractional problems become the classical discrete-time solutions when the fractional order of the discrete-derivatives are integer values, and that they converge to the fractional continuous-time solutions when h tends to zero. Our Legendre type condition is useful to eliminate false candidates identified via the Euler-Lagrange fractional equation. © 2010 Elsevier B.V. All rights reserved.

Prozil S.O.,University of Aveiro | Evtuguin D.V.,University of Aveiro | Lopes L.P.C.,Polytechnic Institute of Viseu
Industrial Crops and Products | Year: 2012

The chemical composition and the structure of macromolecular components of grape stalks from red grape pomaces have been evaluated. These are composed mainly of cellulose (30.3%), hemicelluloses (21.0%), lignin (17.4%), tannins (15.9%) and proteins (6.1%). Among hemicelluloses the xylan was the most abundant (ca. 12%). The parameters of cellulose unitary cell, average diameter of nanofibrils and the degree of crystallinity (75.4%) were assessed by X-ray scattering analysis. The xylan was partially acetylated glucuronoxylan (DS =0.49) possessing the Xyl. p:MeGlc. pA ratio of 25:1. The lignin of grape stalks was suggested to be of HGS type with H:G:S molar proportion of 3:71:26 as revealed by analysis of nitrobenzene oxidation products. Among alkali soluble condensed tannins procyanidins prevailed over prodelphinidins. The abnormal response of grape stalks to kraft pulping, leading to poorly delignified fibrous material, was attributed to a particular lignin structure and it structural association with other macromolecular components of grape stalks. © 2011 Elsevier B.V.

Guine R.P.F.,Polytechnic Institute of Viseu | Barroca M.J.,Polytechnic Institute of Coimbra
Food and Bioproducts Processing | Year: 2012

The present work evaluates the effect of different drying treatments on the color and textural attributes of green bell peppers and pumpkin, which were dried using two different methods: air drying and freeze-drying. The treatments in air drying were carried out at 30 °C and 70 °C. From the results it is possible to conclude that the increase in drying temperature reduced drastically the hardness of green peppers and the freeze drying had an intermediate effect between vegetables dried at 30 °C and 70 °C. Moreover, the springiness was higher in dried green peppers but an opposite effect was observed on chewiness. With respect to pumpkin, any dependence between the fiber orientation and the hardness of the fresh vegetable was not found. In addition, increasing temperature from 30 °C to 70 °C particularly reduced the hardness and the chewiness of dried product and maintained cohesiveness and springiness approximately constant. Regarding the color, it was possible to conclude that air drying at 30 °C produced small changes in color of green pepper whereas air drying at 70 °C and freeze drying originated more intense color changes. The increase of temperature on air drying augmented the color saturation of dried pumpkin while decreased the hue angle by a linear relationship. In addition, the chroma of dried pumpkin decreased significantly with the freeze drying, while the hue angle was maintained constant as compared with the fresh vegetable. © 2011 The Institution of Chemical Engineers.

Guine R.P.F.,Polytechnic Institute of Viseu
Electronic Journal of Environmental, Agricultural and Food Chemistry | Year: 2010

Pears of the variety S. Bartolomeu (Pyrus communis L.) are used in Portugal to produce a traditional food product, obtained by open-air sun drying. The traditional processing has many disadvantages, namely the efficiency and the sanitary quality of the final product. For these reasons, attempts were made to study alternative production methodologies, including the use of a solar stove, a solar drier and a drying tunnel. In this work pears of the variety S. Bartolomeu, were dried in the three alternative systems mentioned, and their drying kinetics was studied. Eight different models from literature were tested and their performance was evaluated in terms of some statistical indicators.The results allowed concluding that the models Henderson & Pabis, Logarithmic and Vega-Lemus were the best to fit the experimental data. Furthermore, it was concluded that the solar drying was very dependent on the weather conditions. It was also possible to observe that the loss of water was much more uniform in the drying tunnel system when compared to the solar dryings, because in the tunnel the operating temperature and air velocity were constant.

Pereira C.C.,Polytechnic Institute of Viseu | Pinho C.,University of Porto
Energy and Fuels | Year: 2013

The fluidized bed reactor is suitable for the combustion of biomass solid fuels because of its advantages in terms of pollution control. At the same time it is a useful laboratory tool to determine kinetic and diffusive combustion data in operating conditions similar to those found in industrial systems. Because of the heterogeneous nature of biomass, available information on its combustion is still limited. During the combustion of ligneous biomass, the burning of the solid carbonaceous residues formed after the initial steps of drying and volatiles release is the time-consuming step. In the present work, kinetic and diffusive data from the fluidized bed combustion of chars produced from four Portuguese wood species - Quercus ilex (holm oak), Eucalyptus globulus (eucalyptus), Pinus pinaster (maritime pine), and Quercus suber (cork oak) - were obtained in the 750-900 C temperature range. Subsequently, activation energies and pre-exponential factors were calculated from the Arrhenius plot of the kinetic data. The obtained activation energies from 38 to 121 kJ/mol are coherent with results obtained for other wood chars and demonstrate that the fluidized bed technology is a fruitful and reliable methodology to achieve a collection of results of real and industrial interest. The main goal of the present work is to widen the information on the kinetic and diffusive data of wood chars in order to better understand the mechanisms of ligneous biomass combustion, and the data now published increases the range of available kinetic data on wood char combustion. © 2013 American Chemical Society.

Paiva J.E.,Polytechnic Institute of Viseu | Paiva J.E.,University of Porto | Carvalho A.S.,Polytechnic Institute of Viseu | Carvalho A.S.,University of Porto
Renewable Energy | Year: 2013

This paper analyses and proposes a different role for small distributed generation (DG) systems based on renewable sources, in the context of modern electrical grids. The main purpose of the system is to act as a grid services provider and not as a stochastic and dynamically unpredictable energy generator. Simulation models are defined and integrated in a hybrid renewable energy system (HRES) with storage, to study its behavior under suitable operation strategies. Being a small system with a production cost higher than a conventional one, its operation as a grid services provider, rather than only an energy generator, is proposed and analyzed firstly by simulation then validated by results from an experimental setup. Carried out results allow concluding that this a suitable system in the current context, either for distributed and smart grids, or for electrical market. © 2012 Elsevier Ltd.

Guine R.P.F.,Polytechnic Institute of Viseu
International Journal of Fruit Science | Year: 2011

In Portugal, pears are traditionally dried by a direct sun exposure method, which has many disadvantages. Therefore, alternative dryings are being tested. The objectives of this study were to evaluate how drying influences some properties of pears: moisture, dimensions, water activity, pH, Brix, acidity, and color. In particular, color is a very important quality attribute of these dried pears. Thus, the different systems should produce products with the same color as the traditional method. The results indicated that the alternative drying methods, if they include sun exposure, allowed us to obtain products similar to the traditional ones. © Taylor & Francis Group, LLC.

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