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Biblioteca Digital do IPB (53.442 recursos)

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PTV - Artigos em Revistas Indexadas ao ISI

Mostrando recursos 1 - 20 de 183

  1. Electrochemical characterization of bioactive hydroxyxanthones by cyclic voltammetry

    Santos, Clementina M.M.; Garcia, Beatriz; Silva, Artur; Santus, René; Morlière, Patrice; Fernandes, Eduarda
    The present study reports the electrochemical behavior of several phenolic and catecholic-substituted 2,3-diarylxanthones on a glassy carbon electrode, challenged by cyclic voltammetry at different pH values (4.0, 7.4, and 11.0). Higher pH values required lower anodic and cathodic peak voltages. The oxidation of catecholic groups occurred at lower peak potentials in a reversible and pH dependent manner. Anodic peak potentials appeared at higher pH values and were attributed to the electrochemically irreversible oxidation of the phenolic groups. The number and position of hydroxyl substituents were the determinants for the electrochemical behavior and found to correlate with the scavenging activity for reactive oxygen (ROS) and nitrogen species (RNS)....

  2. Antioxidant activity and bioactive compounds of lettuce improved by espresso coffee residues

    Cruz, Rebeca; Gomes, Teresa; Ferreira, Anabela; Mendes, Eulália; Baptista, Paula; Cunha, Sara; Pereira, J.A.; Ramalhosa, Elsa; Casal, Susana
    The antioxidant activity and individual bioactive compounds of lettuce, cultivated with 2.5–30% (v/v) of fresh or composted espresso spent coffee grounds, were assessed. A progressive enhancement of lettuce’s antioxidant capacity, evaluated by radical scavenging effect and reducing power, was exhibited with the increment of fresh spent coffee amounts, while this pattern was not so clear with composted treatments. Total reducing capacity also improved, particularly for low spent coffee concentrations. Additionally, very significant positive correlations were observed for all carotenoids in plants from fresh spent coffee treatments, particularly for violaxanthin, evaluated by HPLC. Furthermore, chlorophyll a was a good discriminating factor between control...

  3. Soil management in rainfed olive orchards may result in conflicting effects on olive production and soil fertility

    Ferreira, I.Q.; Arrobas, Margarida; Claro, Ana Marília; Rodrigues, M.A.
    The adoption of a sustainable soil management system is essential for the steep slopes and low fertility soils still supporting rainfed olive orchards in the Mediterranean basin. The effect of the soil management on olive yield, tree nutritional status and soil fertility was studied in a rainfed olive orchard located in NE Portugal that had been managed since its earliest days as a sheep-walk. In 2001, three different soil management systems were established: Sheepwalk, in which the vegetation was managed with a flock of sheep; Tillage, where the vegetation was controlled by conventional tillage; and Glyphosate, where a glyphosate-based herbicide...

  4. Soil nitrogen availability in olive orchards after mulching legume cover crop residues

    Rodrigues, M.A.; Correia, C.M.; Claro, Ana Marília; Ferreira, I.Q.; Barbosa, José Carlos; Moutinho-Pereira, J.M.; Bacelar, E.A.; Fernandes-Silva, Anabela; Arrobas, Margarida
    A natural source of nitrogen (N) is needed to increase soil fertility in traditional olive orchards and to maintain the N nutritional status of olive trees. With this aim, we studied the introduction of legume cover crops in two olive orchards, which were converted into mulches and left on the ground as phytomass after they had been cut. The experiments were carried out in Suçães and Qta do Carrascal, NE Portugal, from October 2009 to January 2012. In Suçães, the ground-cover treatments were lupine (Lupinus albusL.), a mixture of 11 self-reseeding annual legume species, natural vegetation fertilized with 60 kg...

  5. Optimization of mead production using response surface methodology

    Gomes, Teresa; Barradas, Carla; Dias, Teresa; Andrade, João Verdial; Morais, Jorge Sá; Ramalhosa, Elsa; Estevinho, Leticia M.
    The main aim of the present work was to optimize mead production using Response Surface Methodology. The effects of temperature (x1: 20–30 ºC) and nutrients concentration (x2: 60–120 g/hL) on mead quality, concerning the final concentrations of glucose (Y1), fructose (Y2), ethanol (Y3), glycerol (Y4) and acetic acid (Y5), were studied. Twelve operational conditions were tested. No delays and moods were observed during fermentations. The second order polynomial models determined produced satisfactory fittings of the experimental data with regard to glucose (R2= 0.646, p = 0.001), ethanol (R2= 0.741,p = 0.049), glycerol (R2= 0.899, p = 0.002), fructose (R2= 0.902, p =...

  6. Mead production: selection and characterization assays of Saccharomyces cerevisiae strains

    Pereira, Ana Paula; Dias, Teresa; Andrade, João Verdial; Ramalhosa, Elsa; Estevinho, Leticia M.
    http://apps.isiknowledge.com/full_record.do?product=UA&search_mode=GeneralSearch&qid=10&SID=V12mKh9k9n8jHN@CK7o&page=1&doc=1&colname=WOS

  7. Influence of working conditions and practices on fresh-cut lettuce salads quality

    Pereira, Ermelinda; Rodrigues, Ângela; Ramalhosa, Elsa
    The main aim of the present work was to study the influence of working conditions and practices of food handlers on physico-chemical and microbiological quality of fresh-cut lettuce salads produced in a catering unit. Twenty one visits were performed, checking all steps from lettuce reception until fresh-cut lettuce salad preparation. Even though the catering unit has implemented an HACCP plan, some non-conformities were detected on personal hygiene practices of the food handlers that should be corrected. Regarding green salad preparation two sanitizing treatments, diluted solutions of acetic acid (vinegar) and chlorine-based tablets, were applied. However, the former treatment should not be used...

  8. Tremoço - colheita mecânica do grão

    Almeida, Arlindo
    A semente de tremoço é colhida mecanicamente com ceifeiras-debulhadoras, o equipamento comum para colher cereais. Há cerca de trinta anos quando na Austrália a indústria associada ao tremoço teve um incremento significativo, registavam-se perdas de 15% da semente produzida (Riethmuller, 2008). Foram então realizados naquele país vários estudos com o objetivo de conhecer as causas das perdas verificadas e encontrar soluções. As perdas são consequência do uso inadequado do equipamento de colheita. Para as reduzir é necessário efetuar algumas adaptações e regulações nas ceifadeiras-debulhadoras usadas em cereais e escolher de forma criteriosa os dias para a colheita.

  9. Assessment of the oli-picker harvester in Northeast Portugal

    Almeida, Arlindo; Peça, José
    Trunk and bough shakers are common equipment for olive harvesting, and therefore information about their performance is becoming available. For less common equipment like canopy shakers, there is a lack of information relative to their field work capacity. The Oli-picker harvester is commercially available, and operates brushing the tree canopy with a spiked cylindrical coomb mounted on a hydraulic articulated arm, making possible operation, inside or around the olive tree crown. This paper presents results from three years of observation of the Oli-picker harvester in Trás-os-Montes (northeast of Portugal), including the methodologies of work followed in the field, the work rates found...

  10. Application of response surface methodology for obtaining lettuce (Lactuca sativa L.) by-products extracts with high antioxidative properties

    Gomes, Teresa; Delgado, Teresa; Ferreira, Anabela; Pereira, J.A.; Baptista, Paula; Casal, Susana; Ramalhosa, Elsa
    The main objective of the present work was to optimize the extraction conditions for simultaneous maximization of total reducing (TRC) and antioxidant (AC) capacities for lettuce (Lactuca sativa L.) by-products extracts, using response surface methodology. For this, a design of experiments (DOE) with different combinations of solvents (water, methanol and acetone) extraction temperatures (30–60 ◦C) and time (10–60 min) on the TRC and AC was applied. Higher and consistent fittings using second order polynomial models of the experimental data with regard to TRC (R2 = 0.529, p lack of fit > 0.05) and AC (R2 = 0.900, p lack of fit > 0.05)...

  11. Seed oils of ten traditional Portuguese grape varieties with interesting chemical and antioxidant properties

    Fernandes, Luana; Casal, Susana; Cruz, Rebeca; Pereira, J.A.; Ramalhosa, Elsa
    To increase the potential and better exploring of grape seeds that are an important wine-industrial waste, oils of ten traditional Portuguese grape varieties were evaluated in relation to their vitamin E content (tocopherols and tocotrienols), fatty acid profile, as well as, antioxidant properties. Our results showed that the grape-seed oils were a good source of γ-tocotrienol (499–1575 mg/kg), α-tocopherol (85.5–244 mg/kg) and α-tocotrienol (69–319 mg/kg). Concerning fatty acid profile, linoleic (C18:2cc), oleic (C18:1), palmitic (C16:0) and stearic (C18:0) acids were the predominant. Grape-seed oils demonstrated to be a good source of polyunsaturated fatty acids (PUFAs) (63.64–73.53%), whereas monounsaturated fatty acid (MUFA) and...

  12. Vitis vinifera leaves towards bioactivity

    Fernandes, Fátima; Ramalhosa, Elsa; Pires, Patrícia; Andrade, João Verdial; Valentão, P.; Andrade, P.B.; Bento, Albino; Pereira, J.A.
    The majority of the works about Vitis vinifera L. (grape) focus their attention on wine or its major by-product, the grape pomace. Nevertheless, leaves of V. vinifera also constitute an important matrix of this agro-industry. In this study, the chemical composition and antioxidant potential of V. vinifera leaves from twenty Portuguese varieties (white and red) were evaluated for the first time, concerning their reducing total capacity, reducing power and DPPH radical scavenging capacity. The phenolics presente in the aqueous extracts of V. vinifera leaves were trans-caffeoyltartaric and trans-coumaroyltartaric acids, myricetin-3-O-glucoside, quercetin-3-O-glucoside, quercetin-3-O-galactoside and kaempferol-3- O-glucoside, the last two compounds being the most predominant....

  13. Characterization of regional Portuguese kitchens for alheiras de Vinhais (PGI) production with respect to the processing conditions, final product quality and legal framing

    Ramalhosa, Elsa; Magalhães, Ana Luísa; Pereira, Ermelinda
    Alheira de Vinhais is a traditional fermented meat product, produced in the North of Portugal, generally in small units called regional kitchens. In the present study, the requisites established by the European and Portuguese normatives and how these are being applied in these kitchens are discussed. In addition, the evaluation of the hygienic, sanitary and environmental conditions in those establishments, as well as, the microbiological quality of the final product are reported. In order to characterize the processing units, a check-list was applied and microbiological analysis of environmental samples and alheiras were performed. The present work allowed verifying that, despite of some...

  14. Establishment of economic thresholds for olive moth, Prays oleae (Bern.) in Tras-os-Montes region

    Bento, Albino; Torres, L.
    A mathematical model is presented which aims to establish the economic thresholds for the flower generation of olive moth, Prays oleae (Bern.) in Tràs-os- Montes (north-eastern Portugal). The model is based on observations taken between 1993 and 1998, on olives of the oil variety Cobrançosa, grown under rain-fed conditions and without pesticide treatments for several years. It takes into account factors such as cost and efficacy of spraying, environmental impact, expected yield, price and crop losses. According to this model the control of the pest is justified when the percent of flower infestation is between 4.0 % and 6.0 % during the years of intermediate and high expected...

  15. Tetrahydroquinazoline-substituted chromones from Diels–Alder reaction of (E)-2-styrylchromones and pyrimidine ortho-quinodimethane

    Patoilo, Diana; Silva, Artur; Pinto, Diana; Santos, Clementina M.M.; Tomé, Augusto; Cavaleiro, José
    The Diels-Alder reaction of (E)-2-styrylchromones with a pyrimidine ortho-quinodimethane is reported for the first time. These cycloaddition reactions afford mixtures of two regioisomeric tetrahydroquinazoline-substituted chromones in moderate to excellent global yields. Irrespectively of the substituents on the 2-styrylchromones, the 2-(7-aryl-4-methoxy-2-methyl-5,6,7,8-tetrahydroquinazolin-6-yl)chromone derivatives are always the major isomers.

  16. Synthesis and structure elucidation of novel pyrazolyl-2-pyrazolines obtained by the reaction of 3-(3-aryl-3-oxopropenyl)chromen-4-ones with phenylhydrazine

    Santos, Clementina M.M.; Silva, Artur; Jeko, József; Lévai, Albert
    Novel 3-aryl-5-{4-[5-(2-hydroxyphenyl)-1-phenylpyrazolyl]}-2-pyrazolines 2a-g have been prepared by the treatment of 3-(3-aryl-3-oxopropenyl)chromen-4-ones 1a-g with phenylhydrazine in refluxing acetic acid. NMR studies on deuteriochloroform solutions of pyrazolyl-2-pyrazolines 2a-g at different temperatures showed that at room temperature a mixture of diastereomers are present. This diastereoselectivity arises from the combination of the pyrazoline C-4 stereocenter and two planar chiral subunits due to internal steric hindrance. The energy barriers of this steric hindrance were overcome in DMSO-d6 solutions at 60oC. The acetylation of some pyrazolyl-2-pyrazoline derivativess 2a-c,e helped to confirm the presence of the referred mixture of diastereomers.

  17. New improved method for fructooligosaccharides production by Aureobasidium pullulans

    Dominguez, Ana; Nobre, Clarisse; Rodrigues, Lígia R.; Peres, António M.; Torres, Duarte; Rocha, Isabel; Lima, Nelson; Teixeira, José A.
    Fructooligosaccharides are prebiotics with numerous health benefits within which the improvement of gut microbiota balance can be highlighted, playing a key role in individual health. In this study, an integrated one-stage method for FOS production via sucrose fermentation by Aureobasidium pullulans was developed and optimized using experimental design tools. Optimization of temperature and agitation speed for maximizing the FOS production was performed using response surface methodology. Temperature was found to be the most significant parameter. The optimum fermentation conditions were found to be 32 ◦C and 385 rpm. Under these conditions, the model predicted a total FOS production yield of...

  18. Effect of cultivar on sensory characteristics, chemical composition, and nutritional value of stoned green table olives

    Malheiro, Ricardo; Casal, Susana; Sousa, Anabela; Pinho, P. Guedes de; Peres, António M.; Dias, L.G.; Bento, Albino; Pereira, J.A.
    The effect of olive cultivar on sensory characteristics, chemical composition, and nutritional value of traditional stoned green table olives “alcaparras” was studied. The most representative cultivars from Trás-os-Montes region, Portugal (Cv. Cobrançosa, Madural, Negrinha de Freixo, Santulhana, and Verdeal Transmontana) were studied. The results showed that, regardless the cultivar, water was the main constituent with values greater than 70%, followed by fat that varied between 12.5% and 20.1%. Carbohydrates amount was greater in Cv. Madural (9.2%) and those produced from Cv. Cobrançosa had higher level of nitrogenous compounds, with 1.4%. Ashes contents of table olives varied from 1.6% to 1.9%,...

  19. Influence of sampling date on soil nitrogen availability indices

    Arrobas, Margarida; Fonseca, Telmo; Parada, M.J.; Rodrigues, M.A.
    In spite of the great effort that has been devoted to the search for a chemical laboratory index to predict nitrogen (N) mineralization capability of soils, the results have not yet been fully satisfactory. A continued effort is still needed to increase the knowledge of the sources of variation that influence potentially available soil N. The time of sampling has received little attention, taking into account its potential to influence N-mineralization patterns. In this work, soil samples from three different agrosystems, consisting of a double-crop sequence of small grains and maize, an intensively grazed pasture, and a rainfed olive orchard, were collected at different dates. Several chemical extractions...

  20. Ionic regulation and shell mineralization in the bivalve Anodonta cygnea following heavy metal exposure

    Lopes-Lima, Manuel; Freitas, Susana; Pereira, Liliana; Gouveia, Eugénia; Hinzmann, M.; Checa, Antonio; Machado, Jorge
    Freshwater mussels are one of the most imperiled faunistic groups in the world and environmental exposure to toxic heavy metals, which result in deregulation of calcium absorption and deposition in the laboratory, may be a contributing factor in their decline. To address potential effects of heavy-metal exposure on calcium transport and metabolism in freshwater bivalves, adult Anodonta cygnea (L., 1758) were exposed to a sublethal concentration (1.0 × 10−6 mol/L) of essential (Zn2+ and Cu2+) or nonessential (Pb2+ and Cr3+) metal for 30 days in the laboratory. Inorganic composition of extrapallial, haemolymph, heart, and pericardium fluids, and kidney tissue, as...

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