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Evaluation of the effect of high pressure on total phenolic content, antioxidant and antimicrobial activity of citrus peels

Publication . Casquete, Rocío; Castro, Sónia Marilia; Martín, Alberto; Ruiz-Moyano, Santiago; Saraiva, Jorge A.; Córdoba, María G.; Teixeira, Paula

This study aimed to assess the effect of high pressure at 300 and 500 MPa for 3 and 10 min on the phenolic compounds, antioxidant capacity and antimicrobial activity of citrus peel extracts. Total phenolic contents (TPC) and antioxidant properties of extracts were determined as free radical-scavenging ability of DPPH and using the ABTS radical cation decolorization assay. Additionally, extracts were tested for antimicrobial activity against twenty different strains of bacteria representing both Gram-positive and Gram-negative types. Citrus peel extracts demonstrated antimicrobial activity against a wide range of bacteria. The maximum level of TPC as well as antioxidant capacity were observed at 300 MPa for 3 min. Citrus peels extracts demonstrated antimicrobial activity against a wide range of microorganisms. The antimicrobial activity of orange peel extract was the highest among the four citrus peels studied. Generally, bacteria Acinetobacter and the strain Listeria innocua were more sensitive to the peel extracts.

2015Journal article

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Influence of the temperature and oxygen exposure in red Port wine: a kinetic approach

Publication . Oliveira, Carla Maria; Barros, António S.; Ferreira, António César Silva; Silva, Artur M. S.

Although phenolics are recognized to be related with health benefits by limiting lipid oxidation, in wine, they are the primary substrates for oxidation resulting in the quinone by-products with the participation of transition metal ions. Nevertheless, high quality Port wines require a period of aging in either bottle or barrels. During this time, a modification of sensory properties of wines such as the decrease of astringency or the stabilization of color is recognized to phenolic compounds, mainly attributed to anthocyanins and derived pigments. The present work aims to illustrate the oxidation of red Port wine based on its phenolic composition by the effect of both thermal and oxygen exposures. A kinetic approach toanthocyanins degradation was also achieved. For this purpose a forced red Port wine aging protocol was performed at four different storage temperatures, respectively, 20, 30, 35 and 40 degrees C, and two adjusted oxygen saturation levels, no oxygen addition (treatment I), and oxygen addition (treatment II). Three hydroxycinnamic esters, three hydroxycinnamic acids, three hydroxybenzoic acids, two flavan-3-ols, and six anthocyanins were quantitated weekly during 63 days, along with oxygen consumption. The most relevant phenolic oxidation markers were anthocyanins and catechin-type flavonoids, which had the highest decreases during the thermal and oxidative red Port wine process. Both temperature and oxygen treatments affected the rate of phenolic degradation. In addition, temperature seems to influence mostly the phenolics kinetic degradation.

2015Journal article

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High pressure extraction of phenolic compounds from citrus peels

Publication . Casquete, R.; Castro, Sónia; Villalobos, M.C.; Serradilla, M.J.; Queirós, R.P.; Saraiva, J.A.; Córdoba, M.G.; Teixeira, Paula

This study evaluated the effect of high pressure processing on the recovery of high added value compounds from citrus peels. Overall, the total phenolic content in orange peel was significantly (P <.05) higher than that in lemon peel, except when pressure treated at 500MPa. However, lemon peel demonstrated more antioxidant activity than orange peel. Pressure-treated samples (300 MPa, 10min; 500 MPa, 3min) demonstrated higher phenolic content and antioxidant activity comparatively to the control samples. For more severe treatments (500MPa, 10min), the phenolic content and antioxidant activity decreased in both lemon and orange peels.

2014Journal article

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Hydrogels containing porphyrin-loaded nanoparticles for topical photodynamic applications

Publication . González-Delgado, José A.; Castro, Pedro M.; Machado, Alexandra; Araújo, Francisca; Rodrigues, Francisca; Korsak, Bárbara; Ferreira, Marta; Tomé, João P.C.; Sarmento, Bruno

5,10,15,20-tetrakis(1-methylpyridinium-4-yl)-porphyrin tetra-iodide (TMPyP), a potent water-soluble photosensitizer (PS) used in antimicrobial applications, was encapsulated into poly(lactic-co-glycolic acid) (PLGA) nanoparticles (TMPyP-PLGA) for topical delivery purposes. Nanoparticles resulted in a mean particle size around 130nm, narrow polydispersity index (PdI), spherical morphology and association efficiency up to 93%. Free TMPyP and TMPyP-PLGA nanoparticles were incorporated into Carbopol(®) hydrogels, resulting in controlled TMPyP release of about 60% and 20% after 4.5h, respectively. Critical properties such as appearance, clarity, viscosity and pH were maintained over time, as hydrogels were stable during 6 months at 4°C, 25°C/60% RH and 40°C/75% RH. For photodynamic applications, the photoproduction of singlet oxygen from these hydrogels was quite efficient being both formulations very photostable after 20min. No TMPyP permeation through pig ear skin was observed after 24h, and histological assays did not show relevant damages in surrounding tissues. All these excellent characteristics make them promising platforms for photodynamic applications through topical clinical use.

2016Journal article

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