Mostrando recursos 1 - 20 de 131

  1. Metastability of Multi-Lamellar Vesicles in a Nonionic System

    Filippelli, L.; Rossi, C. O.; Miguel, Maria Graça; Olsson, U.
    Nuclear magnetic resonance spectroscopy and rheological analysis have been used to investigate the stability of mechanically induced tri-ethylene-glycol-mono-n-decyl-ether (C(10)E(3))/deuterium oxide (D(2)O) multi-lamellar vesicles (MLVs) and the transition from MLVs to planar lamellae. It was found that MLVs prepared by vortex stirring, relax back to the lamellar phase in a few hours while the relaxation of the shear induced MLVs takes days. Pulsed gradient spin echo and water self-diffusion coefficient experiments, revealed that the MLVs texture, obtained by vortex stirring, is composed of large size structures. These data indicate that the kinetics of lamellar re-formation depend on the MLVs number density.

  2. Reversible size of shear-induced multi-lamellar vesicles

    Fujii, S; Richtering, W; Miguel, Maria Graça; Olsson, U
    We have investigated the reversibility in the shear-induced multi-lamellar vesicle (MLV) size during stepwise cycling of the shear rate by employing common rheometry, polarized light microscopy and rheo-optic techniques. We thus address the question whether there is a true MLV steady state, irrespective of history. The system studied, was the nonionic surfactant triethylene glycol decyl ether (C(10)E(3)) with a concentration of 40 wt.% in D(2)O and a constant temperature of 25 degrees C. It was found that the MLV size varies reversibly with varying shear rate, and hence there exists a true steady state in the presence of shear flow....

  3. How does a non-ionic hydrophobically modified telechelic polymer interact with a non-ionic vesicle? Rheological aspects

    Dos Santos, T; Antunes, Fe; Lindman, B; Miguel, Maria Graça
    The association between hydrophobically modified polyethylene glycol, HM-PEG, and non-ionic vesicles of tetraethylene glycol monododecyl ether, C12E4, was investigated. HM-PEG is in a triblock form, with an alkyl chain attached to each hydrophilic polymer-end. Such polymer structure is denoted as telechelic. The vesicle average radius was measured by self-diffusion measurements. The system exhibits both a monophasic gel and biphasic regions. The monophasic region was characterized from a theological point of view. We argue that the gel formation is due to the presence. of polymer crosslinks between different surfactant aggregates, once the polymer's hydrophobic moieties may adsorb into the vesicle bilayer....

  4. Effect of storage time at low temperature on the volatile compound composition of Sevillana and Maravilla raspberries

    Morales, M. L.; Callejon, R. M.; Ubeda, C.; Guerreiro, A. C.; Gago, C. M. L.; Miguel, Maria Graça; Antunes, Maria Dulce
    In this study, the effect of storage time at low temperature on volatile compounds in two cultivars of raspberry, Rubus idaeus L. cv. Sevillana and Maravilla, was determined. A total of 28 compounds were identified in both cultivars and showed quantitative differences between the cultivars. The Sevillana cultivar was richer in volatile compounds than the Maravilla cultivar. beta-Ionone had the highest concentration in both cultivars. We observed opposing trends in the volatile compound composition for the cultivars during storage at low temperature, in which 'Sevillana' lost compounds and 'Maravilla' was enriched. Therefore, storage at low temperature causes important changes in...

  5. Refrigeration needs for sustainable preservation of horticultural products

    Sousa, A. R.; Juliao, M.; Miguel, Maria Graça; Antunes, Maria Dulce; Panagopoulos, Thomas
    Fresh horticultural products are highly perishable and need refrigeration for further preservation. Refrigeration needs energy consumption with consequent economical cost and damage for the environment. The objective of the present work was to use efficiently the refrigeration according to the product needs and time for consumption. Salicornia ramosissima and Sarcocornia perennis fresh branch tips, which are used for fresh salads, were stored at 1, 4 and 9 °C for up to 21 days. In both species, fresh tips were of good consumer acceptability for up to 14 days at 9°C. At 1 and 4 °C fresh tips could be stored...

  6. Stability of Fried Olive and Sunflower Oils Enriched with Thymbra capitata Essential Oil

    Miguel, Maria Graça; Antunes, Maria Dulce; Rohaim, A.; Figueiredo, A. C.; Pedro, L. G.; Barroso, J. G.
    The stability of olive and sunflower oils for domestic uses after frying cow steak or only heating were evaluated in the presence or absence of the carvacrol-rich essential oil of Thymbra capitata. The treatments consisted of sunflower and olive oils either enriched with 200 mg/l of T. capitata oil or without it, heating at 180°C for 20 min, or frying 100 g cow steak at the same temperature and for the same period of time. In all assays, acid, peroxide, and p-anisidine values were followed over time. The fatty acid profile was estimated before heating or frying as well as...

  7. Antioxidant, anti-inflammatory and anti-acetylcholinesterase activities of eleven extracts of Moroccan plants

    Miguel, Maria Graça; Bouchmaa, N.; Aazza, S.; Gaamoussi, F.; Lyoussi, B.
    The capacity of ethanolic extracts of wHaloxylon scoparium Pomel, Corrigiola telephiifolia Pourr., Ammodaucus leucotrichus Cosson & Durieu subsp. leucotrichus, Chamaerops humilis L., Sideritis arborescens Salzm. ex Benth., Ammi visnaga (L.) Lam., Vitex agnus castus L., Retama raetam (Forssk.) Webb & Berthel., Berberis vulgaris L., Viscum album L., and Equisetum arvense L. from Morocco to prevent lipid peroxidation, scavenging free radicals, inhibiting lipoxygenase and acetylcholinesterase activities, were evaluated and compared to those reported in the literature. As far as we know, the present work was the first reporting on the antioxidant ability of S. arborescens. The results showed that Equisetum arvense...

  8. Composition of the essential oils of Thymus and Origanum species from Algeria and their antioxidant and antimicrobial activities

    Hazzit, M.; Baaliouamer, A.; Faleiro, Leonor; Miguel, Maria Graça
    The composition of the essential oils of Origanum and Thymus species restricted to Algeria and the North Africa region was determined. Antioxidant and antibacterial activities of the isolated essential oils were also determined. The oils of oregano plants were strongly characterized by p-cymene (16.8-24.9%), gamma-terpinene (16.8-24.9%), thymol (8.4-36.0%), and carvacrol (1.1-29.7%), a thymol chemotype for Origanum floribundum and a R-terpineol chemotype for Thymus numidicus being described for the first time. The strains of Listeria monocytogenes tested were relatively resistant to the action of essential oils of either Origanum or Thymus species. All essential oils possessed antioxidant activity, but this was...

  9. Antioxidant activity of thymbra capitata essential oil in meat-treated oil

    Mohammed, A. D.; Miguel, Maria Graça; Antunes, Maria Dulce; Figueiredo, A. C.; Pedro, L. G.; Barroso, J. G.
    Several synthetic antioxidants such as butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), and tertiary butyl hydroquinone (TBHQ), have been used to preserve meat. Nevertheless they are considered toxic and to have carcinogenic effects. Natural products, such as those present in essential oils, have been the target of studies as alternative antioxidants, showing promising results. In addition, these natural compounds have the advantage of having consumer's acceptance. Thymbra capitata is a perennial, herbaceous shrub commonly used as a spicy herb. The essential oils isolated from this plant showed antimicrobial and antioxidant activities. The main goal of the present work was to evaluate...

  10. Strawberry recovers from iron chlorosis after foliar application of a grass-clipping extract

    Pestana, M.; Domingos, I.; Gama, F.; Dandlen, S. A.; Miguel, Maria Graça; Pinto, J. C.; De Varennes, A.; Correia, P. J.
    Bare-root transplants of strawberry (Fragaria x ananassa Duch. cv. Selva) were transferred to nutrient solutions with or without iron. After 35 d of growth, plants in the solution without iron became chlorotic and had morphological changes in roots typical of iron-deficiency chlorosis (IDC). Acidification of the nutrient solution was also observed. We tested a grass-clipping extract to correct IDC in strawberry plants by foliar application to some chlorotic plants. We also assessed the effects of this product on plant growth, Fe allocation, as well as morphological and physiological parameters related with IDC. After the second spray, leaf chlorophyll increased in...

  11. Essential oil composition of Thymus lotocephallus G. Lopez & R. Morales, collected during flowering and vegetative phases

    Figueiredo, A. C.; Miguel, Maria Graça; Duarte, A. M. F.; Barroso, J. G.; Pedro, L. G.
    The aerial parts of Thymus lotocephalus were collected during the flowering and vegetative phases of the plant in the Algarve, Portugal. The oils were isolated by hydrodistillation and distillation-extraction and analysed by GC and GC-MS. The oil isolated from the flowers was obtained in a yield of 0.9%, whereas those isolated from the leaves during flowering and vegetative phases showed lower yields, 0.7% and 0.2% (v/w), respectively. The oils isolated from both the flowers and the leaves were dominated by the oxygen-containing monoterpenes (57-64%). The monoterpene hydrocarbons (11-22%) and the oxygen-containing sesquiterpenes (7-14%) were the two other main fractions of...

  12. Composition and antioxidant activities of the essential oils of Thymus caespititius, Thymus camphoratus and Thymus mastichina

    Miguel, Maria Graça; Simões, M.; Figueiredo, A. C.; Barroso, J. G.; Pedro, L. G.; Carvalho, L. M.
    The essential oils, isolated by hydrodistillation, from the aerial parts of Thymus caespititius, Thymus camphoratus and Thymus mastichina, collected during the vegetative phase, were analysed by gas chromatography (GC) and gas chromatography coupled to mass spectrometry (GC-MS). The antioxidant property of these oils was tested, with and without peroxidation inducer, by the egg yolk-based thiobarbituric acid-reactive substances assay, in the concentrations of 62.5, 125, 250 and 500 mg l(-1). alpha-Terpineol (32%) dominated Th. caespititius essential oil and 1,8-cineole (58%) that of Th. mastichina. Linalool (17%), linalyl acetate (15%) and 1,8-cineole (11%) were the main components of Th. camphoratus oil. The...

  13. Volatile-Oils Composition, and Bioactivity of the Essential Oils of Plectranthus barbatus, P. neochilus, and P. ornatus Grown in Portugal

    Mota, L.; Figueiredo, A. C.; Pedro, L. G.; Barroso, J. G.; Miguel, Maria Graça; Faleiro, Leonor; Ascensão, L.
    Volatile-oils chemical composition and bioactivity of the essentail oils from Plectranthus barbatus, P. neochilus, and P. ornatus (Lamiaceae) were assessed. Aerial parts from these three related Plectranthus species were collected from cultivated plants grown in Portugal, during vegetative and flowering phases. Volatiles, isolated by distillationextraction, were analyzed by GC and GC/MS. Monoterpene hydrocarbons (12-74%) and sesquiterpene hydrocarbons (4-45%) constituted the main fractions in all volatiles. -Pinene (3; 12-67%), oct-1-en-3-ol (6; traces-28%), -pinene (7; 0.1-22%), and -caryophyllene (50; 7-12%) dominated P. barbatus volatiles. P. neochilus major volatile components were -terpenyl acetate (41; traces-48%), -thujone (2; 2-28%), -caryophyllene (50; 2-28%), -pinene (7;...

  14. Essential oils from anethum graveolens, Levisticum officinale and pimpinella anisum hairy root cultures: Composition, antibacterial and antioxidant activities

    Costa, Mm; Bounatirou, S; Miguel, Maria Graça; Faleiro, Ml; Figueiredo, Ac; Barroso, Jg; Pedro, Lg; Deans, Sg; Scheffer, Jjc

  15. Effect of 1-Methylcyclopropene Application Prior to Storage on Fresh-Cut Kiwifruit Quality

    Antunes, Maria Dulce; Miguel, Maria Graça; Metelo, S; Dandlen, Sa
    Kiwifruit is commercially important as fresh-cut. The purpose of this work was to study the effect of 1-methylcyclopropene (1-MCP) applied after harvest, before storage, on the posterior behaviour of ripe fruit prepared as fresh-cut. Harvested fruit where treated with 1 mu l L(-1) 1-MCP for 20 hours at room temperature, then stored at 0 C. After 3 months, fruit were removed from storage, peeled and cut longitudinally in quarters, then stored at 2 C for 8 days. Measurements of flesh colour, firmness, soluble solids content (SSC), electrolyte leakage and ascorbic acid were performed after 0, 4 and 8 days. Kiwifruit...

  16. Influence of Citric Acid, Ascorbic Acid and Calcium Lactate Applications on the Shelf Life of Minimally Processed Horticultural Products

    Rodrigues, Dac; Miguel, Maria Graça; Dandlen, Sa; Nunes, S; Antunes, Maria Dulce
    The market share of minimally processed fruits and vegetables has continuously increased in the past years due to consumer life style. These products have high expectations regarding quality and shelf-life. The objective of the present work was to evaluate the effect of additives applied externally after cutting in fresh-cut kiwifruit, pears, strawberries, tomatoes, and peppers. Fruit were washed in water, cut longitudinally in quarters and dipped in solutions of 2% citric acid, 2% ascorbic acid or 2% calcium lactate. Subsequently, fruit were packed in plastic trays, covered with 15 mu m thick polyethylene film and stored at 4 degrees C...

  17. Antioxidant and Antiacetylcholinesterase Activities of Some Commercial Essential Oils and Their Major Compounds

    Aazza, S.; Lyoussi, B.; Miguel, Maria Graça
    The commercial essential oils of Citrus aurantium L., Cupressus sempervirens L., Eucalyptus globulus Labill., Foeniculum vulgare Mill. and Thymus vulgaris L., isolated by steam distillation by a company of Morocco were evaluated in terms of in vitro antioxidant activity through several methods. In vitro acetylcholinesterase inhibitory activity was also determined. Citrus limon (L.) Burm. f. oil was also studied, but it was obtained by peel expression. The best antioxidant was T. vulgaris oil, independent of the method used, mainly due to the presence of the phenolic monoterpenes thymol and carvacrol, which when studied as single compounds also presented the best...

  18. Foliar treatments as a strategy to control iron chlorosis in orange trees

    Pestana, M.; Correira, P. J.; Miguel, Maria Graça; De Varennes, A.; Abadia, J.; Faria, E. D.
    Different foliar treatments were applied to evaluate the recovery of iron chlorosis of orange trees (Citrus sinensis (L.) Osb. cv. 'Valencia late') grown on a calcareous soil. The treatments were: Fe (II) sulphate (500 mg Fe L-1), sulphuric acid (0.5 mM H2SO4), Fe (III)-chelate (Hampiron 654 GS, 120 mg Fe L-1) and distilled water as a control. The recovery from iron chlorosis was evaluated with the SPAD-502 apparatus and the values converted to total chlorophyll concentration. The effects of treatments on the mineral composition of leaves and flowers, and the size and quality of fruits were evaluated. The residual effect...

  19. Comparison of the main components of the essential oils from flowers and leaves of Thymus mastichina (L.) L. ssp mastichina collected at different regions of Portugal

    Miguel, Maria Graça; Duarte, F.; Venancio, F.; Tavares, R.
    The chemical composition of the essential oils from the leaves and the flowers of Thymus mastichina collected at different regions of Portugal were analyzed by GC and GC/MS. It revealed that fresh flowers produce larger amounts of oils than the leaves. The highest oil yields were obtained from the flowers collected at Arrabida (3.5%, and Mertola (3.0%, v/w). Two types of oils were differentiated according to their main components. Oils rich in 1,8-cineole whose concentrations ranged from 39.4% (in the flower oils collected at Mertola) to 69.2% (in the leaf oils from Arrabida), and an oil rich in linalool (73.5%)...

  20. Evaluation of Fe deficiency effects on strawberry fruit quality

    Gama, F; Saavedra, T; Miguel, Maria Graça; Dandlen, Sa
    The effects of Fe deficiency on the antioxidant properties of strawberry juice was carried out with a day-neutral cultivar 'Selva'. Bare root transplants (without leaves) with approximately 18 cm, were transferred to Hoagland's nutrient solution with (Fe2.5) and without Fe (Fe0), using Fe-EDDHMA as the Fe source: 0 and 2.5 5 μM Fe. Plants were grown in 20 L containers in a glasshouse for 6 weeks (from April 27 to June 5) under natural light and air temperature ≤ 25°C. Twelve transplants were used per treatment, distributed in a complete randomized design. Plants grown in absence of Fe revealed chlorotic...

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