Percorrer por autor "Santos, Pedro M.P."
A mostrar 1 - 10 de 24
Resultados por página
Opções de ordenação
- Absorbed dose and effective dose in food irradiation: measurement and validation with different phantomsPublication . Antonio, Amilcar L.; Santos, Pedro M.P.; Bento, Albino; Quintana, BegoñaFood products are processed by different technologies in order to increase its safety and shelflife. Food irradiation is regulated in European Union by the Directive 1999/2/EC, approved by international organizations of food (FAO – Food and Agriculture Organization) and health (WHO – World Health Organization) and the demand for post-harvest processed food products without use of chemicals could be an opportunity to boost irradiation technologies, that are already currently used for food preservation, namely for ripening delay, insects’ disinfestation or food decontamination. Before starting an irradiation process a dosimetric study is always performed to characterize the absorbed dose taking in account food product characteristics, namely bulk and volumetric density, in order to guarantee the desired effect, without compromising the main physicochemical parameters. The dose inside the food product can only be assessed indirectly or estimated by computational methods. The effective dose, a concept used more in human radiotherapy, takes in account the type of radiation and tissue. In food irradiation the effective dose could be estimated from the absorbed dose, considering the physical characteristics of the product. The irradiations of food and food phantoms were performed in a Co-60 experimental chamber, with a total activity of 198 TBq (5.33 kCi) in November 2012 (Precisa 22, Graviner Manufacturing Company Ltd, U.K.). The dose was estimated for each fruit in three different positions in the chamber and the values of absorbed dose were obtained by spectrophotometric methods, using previous calibrated routine Amber Perspex dosimeters (batch V, from Harwell Company, U.K.). Using an experimental approach, the estimated absorbed dose for different phantoms are presented and corrected with the physical characteristics, dimensions, density and radiation mass attenuation coefficient of the food product to obtain the effective dose, that could be used to better characterize the irradiation process.
- Aplicação das fórmulas CIELAB e CIEDE2000 na avaliação da cor de folhas vegetais irradiadas por uma fonte de Cobalto-60Publication . Pinela, José; Antonio, Amilcar L.; Santos, Pedro M.P.; Cabo Verde, Sandra; Carvalho, Ana Maria; Ferreira, Isabel C.F.R.A cor dos alimentos está directamente associada à sua aceitação pelo consumidor. A procura de métodos de processamento seguros e eficazes destaca a radiação ionizante, já que permite a desinfecção do alimento e a extensão do seu tempo de prateleira [1]. O espaço de cor CIELAB é comummente utilizado para avaliar diferenças de cor (ΔE*) entre dois objectos. No entanto, a fórmula CIEDE2000 permite atenuar variações entre valores calculados e percepcionados [2]. O impacto da radiação ionizante na cor de um vegetal folhoso foi avaliado durante o tempo de armazenamento e os resultados discutidos utilizando ambas as fórmulas de ΔE*.
- Assessment of gamma radiation effects on antioxidant activity of cork wastewaterPublication . Madureira, Joana; Pimenta, Andreia I.; Dias, Maria Inês; Melo, Rita; Santos, Pedro M.P.; Falcão, António N.; Cabo Verde, Sandra; Ferreira, Isabel C.F.R.; Margaça, Fernanda M.A.Cork cooking wastewater results from the process of boiling cork planks. It is an aqueous and complex dark liquor with high concentration of phenolic compounds such as phenolic acids and tannins [1, 2], which are known for their high antioxidant activity. The aim of this work is to perform a compreensive assessment of the effects of gamma radiation on the antioxidant activity of cork cooking water. The irradiation experiments were carried out at room temperature in a Co-60 experimental equipment (Prescisa 22, Graviner, Lda, UK), with an activity of 140 Tbq (3.77 kCi) and at a dose rate of 1.5 kGy/h, located at the Centro de Ciências e Tecnologias Nucleares (Portugal). Samples of wastewater were irradiated at. three distinct. doses (10, 20 and 50 KGy) and the antioxidant activity was evaluated by in vitro assays based on different mechanisms of action: DPPH radical scavenging activity, reducing power and inhibition of β-carotene bleaching. Antioxidant capacity was compared with the physico-chemical characterization [3) of cork wastewater - Chemical Oxygen Demand (COD), Biochemical Oxygen Demand (BOD), Total Suspended Solids (TSS) and Total Phenolic Content. (TP) - when exposed to gamma radiation. The obtained results point out that gamma radiation induces changes in complex compounds leading to an increase in the antioxidant capacity. These results demonstrate the potential of this technology in order to increase the added value of cork wastewaters.
- Combined effects of irradiation and storage time on the nutritional and chemical parameters of dried Agaricus bisporus Portobello mushroom flourPublication . Cardoso, Rossana V.C.; Carocho, Márcio; Fernandes, Ângela; Barreira, João C.M.; Cabo Verde, Sandra; Santos, Pedro M.P.; Antonio, Amilcar L.; Gonzaléz-Paramás, Ana M.; Barros, Lillian; Ferreira, Isabel C.F.R.Abstract: Portobello variety of Agaricus bisporus mushrooms, appreciated for its taste, makes it desirable to be eaten fresh and also as flour in soups and gravies. Gamma and electron-beam radiation at four doses (1, 2, 5, and 10 kGy) were used to analyze its preservation effect on Portobello mushroom flour. A proximate analysis, as well as the impact on fatty acids, tocopherols, soluble sugars, organic acids, and ergosterol profiles, were performed every 3 months, during a storage period of 1 year. Gamma rays preserved mannitol (most abundant soluble sugar) over the 12 months, while electron beam radiation preserved organic acids. No significant changes were sought for any radiation type, and the slight changes extracted from the estimated marginal means reveal a tendency for irradiation as having preserving effects of nutrients and other important molecules. Thus, both irradiation types, up to 10 kGy are suitable for preservation of A. bisporus Portobello flour.
- Combined effects of irradiation and storage time on the nutritional and chemical parameters of dried Agaricus bisporus Portobello mushroom flourPublication . Cardoso, Rossana V.C.; Carocho, Marcio; Fernandes, Ângela; Barreira, João C.M.; Cabo Verde, Sandra; Santos, Pedro M.P.; Antonio, Amilcar L.; Gonzaléz‐Paramás, Ana M.; Barros, Lillian; Ferreira, Isabel C.F.R.Portobello variety of Agaricus bisporus mushrooms, appreciated for its taste, makes it desirable to be eaten fresh and also as flour in soups and gravies. Gamma and electron-beam radiation at four doses (1, 2, 5, and 10 kGy) were used to analyze its preservation effect on Portobello mushroom flour. A proximate analysis, as well as the impact on fatty acids, tocopherols, soluble sugars, organic acids, and ergosterol profiles, were performed every 3 months, during a storage period of 1 year. Gamma rays preserved mannitol (most abundant soluble sugar) over the 12 months, while electron beam radiation preserved organic acids. No significant changes were sought for any radiation type, and the slight changes extracted from the estimated marginal means reveal a tendency for irradiation as having preserving effects of nutrients and other important molecules. Thus, both irradiation types, up to 10 kGy are suitable for preservation of A. bisporus Portobello flour.
- Degradation of compounds present in cork boiling water by gamma radiationPublication . Madureira, Joana; Barros, Lillian; Melo, Rita; Santos, Pedro M.P.; Falcão, António N.; Cabo Verde, Sandra; Ferreira, Isabel C.F.R.; Margaça, Fernanda M.A.Cork boiling water is an aqueous and complex dark liquor with high concentration of phenolic compounds such as phenolic acids and tannins [1, 2], which are considered biorecalcitrants [2]. Ionizing radiation has been widely studied as an alternative technology for the degradation of organic contaminants without the addition of any other (e.g.: Fenton technologies). The aim of this work was to identify the compounds present in cork boiling water and further evaluate the resulting stable degradation products after gamma irradiation. The irradiation experiments of standard solutions were carried out at room temperature using a Co-60 experimental equipment. The applied absorbed doses were 20 and 50 kGy at a dose rate of 1.5 kGy/h, determined by routine dosimeters [3]. The identification of radiolytic products was carried out by HPLC-DAD-ESI/MS. The phenolic compounds were identified by comparing their retention times and UV–vis and mass spectra with those obtained from standard compounds, when available, as well as by comparing the obtained information with available data reported in the literature. Concerning the obtained results and the literature review, the main cork wastewater components are: quinic, gallic, protocatechuic, vanillic, syringic and ellagic acids. Based on this, we used protocatechuic, vanillic and syringic acids as model compounds to study their degradation by gamma radiation in order to identify the corresponding radiolytic products. Standard aqueous solutions were irradiated and the derivatives of each model compound are represented in figure 1. The obtained results seem to demonstrate that the derivatives of the parent compounds could also be phenolic acids, since it was observed the loss of 44 u (CO2) from the [M-H]- ions. Gallic and protocatechuic acids are identified as derivatives of vanillic and syringic acids, and gallic acid as a protocatechuic acid derivative. Compound 5 ([M-H]- at m/z 169) was tentatively identified as 2,4,6-trihydroxybenzoic acid, since its fragmentation pattern (m/z 151, 125 and 107) is similar to that previously reported in literature [4]. The structure of compound 7 was proposed based on the molecular ion and its fragmentation and compound 6 remains unknown.
- Dosimetric characterization of a multipurpose experimental Gamma chamberPublication . Antonio, Amilcar L.; Carocho, Márcio; Santos, Pedro M.P.; Cabo Verde, Sandra; Bento, Albino; Botelho, M. Luísa; Quintana, BegoñaIonizing radiation is used as an industrial process for different purposes: sterilization, disinfestation, increase food products shelf life or for materials modification. Each industrial use is preceded by a validation process, to study the impact of the radiation on the product characteristics. At Nuclear and Technological Campus, Portugal, an experimental gamma chamber with four Co-60 sources, with a total activity of 4.79 kCi (in Nov. 2012) and four levels for irradiation, is used for different research studies in food irradiation, waste water treatment, polymerization and sterilization. Recently, in 2009, the experimental chamber was re-charged with new sources, and since then a continuous work has been done for the complete characterization of the different irradiation positions and levels. In the present study, the dose rate for each level and position was estimated using an Ionization Chamber (from IBA-dosimetry corporation). The estimated doses and a three dimensional dose mapping is presented for the four levels of the chamber. This dose mapping allows an enhanced optimization and implementation of irradiation processes, namely for food irradiation.
- Effects of Electron Beam Radiation on the Phenolic Composition and Bioactive Properties of Olive Pomace ExtractsPublication . Madureira, Joana; Gonçalves, Inês; Cardoso, Jéssica; Dias, Maria Inês; Santos, Pedro M.P.; Margaça, Fernanda M.A.; Santos-Buelga, Celestino; Barros, Lillian; Cabo Verde, SandraOlive pomace is an agro-industrial waste product generated from the olive oil industry and constituted by bioactive compounds with potential applications in several industrial sectors. The purpose of this work was to evaluate the effects of electron beam (e-beam) radiation on olive pomace, specifically on phenolic compounds (by HPLC-DAD-ESI/MS) and the bioactive properties (antioxidant, antiproliferative, and antimicrobial activities) of crude olive pomace (COP) and extracted olive pomace (EOP) extracts. The amount of total flavonoid content and the reducing power of COP extracts were higher than those obtained for EOP extracts. The results suggested that e-beam radiation at 6 kGy increased both total phenolic and total flavonoid contents as well as the reducing power of COP extracts, due to the higher extractability (>2.5-fold) of phenolic compounds from these samples, while decreasing the scavenging activity of extracts. The extracts of both olive pomaces showed antibacterial potential, and COP extracts at 400 mu g/mL also presented antiproliferative activity against A549, Caco-2, 293T, and RAW264.7 cell lines, with both properties preserved with the e-beam treatment. All in all, e-beam radiation at 6 kGy appears to be a promising technology to valorize the pollutant wastes of the olive oil industry through enhancing phenolic extractability and bioactive properties, and, furthermore, to contribute to the environmental and economical sustainability of the olive oil industry.
- Effects of gamma radiation on cork wastewater: Antioxidant activity and toxicityPublication . Madureira, Joana; Pimenta, Andreia I.; Popescu, Larisa; Besleaga, Alexandra; Dias, Maria Inês; Santos, Pedro M.P.; Melo, Rita; Ferreira, Isabel C.F.R.; Cabo Verde, Sandra; Margaça, Fernanda M.A.A comprehensive assessment of the toxicity and antioxidant activity of cork boiling wastewater and the effects of gamma radiation on these parameters was performed. Antioxidant activity was evaluated using different methodologies as DPPH radical scavenging activity, reducing power and inhibition of ß-carotene bleaching. The results have shown that gamma radiation can induce an increase on the antioxidant activity of cork boiling wastewater. Toxicity tests were performed to access the potential added value of the irradiated wastewaters and/or minimization of the impact for discharge in the environment. Two different methods for toxicity evaluation were followed, bacterial growth inhibition test and cytotoxicity assay, in order to predict the behavior of different cells (prokaryotic and eukaryotic) in the presence of cork wastewater. Non-treated cork boiling wastewater seemed to be non-toxic for prokaryotic cells (Pseudomonas fluorescens and Bacillus subtilis) but toxic for eukaryotic cells (A549 human cells and RAW264.7 mouse cells). The gamma radiation treatment at doses of 100 kGy appeared to increase the toxicity of cork compounds for all tested cells, which could be related to a toxic effect of radiolytic products of cork compounds in the wastewaters.
- Electron-beam irradiation preserves nutritional profile of Agaricus bisporus PortobelloPublication . Cardoso, Rossana V.C.; Fernandes, Ângela; Barreira, João C.M.; Antonio, Amilcar L.; Santos, Pedro M.P.; Cabo Verde, Sandra; Paramás, Ana M.G.; Barros, Lillian; Ferreira, Isabel C.F.R.All over the world, mushrooms are highly consumed due to their high contents of digestible proteins, carbohydrates, vitamins and fibers. Mushrooms contain about 90% of water, which leads to a faster deterioration due to senescence, browning, water loss and microbial attack. Despite of the immense popularity of this food worldwide, data regarding alternative technologies to increase mushrooms shelf-life are scarce. Ionizing radiation processing is recognized as a safe and effective method for conservation, being widely used to extend the shelf-life of raw foods. The present work reports the effects of storage time (0, 4 and 8 days) and electron-beam irradiation on the nutritional composition (moisture, fat, proteins, ash, carbohydrates and energy) of Agaricus bisporus Portobello samples. The irradiation was performed with a 10 MeV energy irradiator at the doses of 1, 2 and 5 kGy. The proximate composition was evaluated by AOAC official procedures. Storage time (ST) and electron-beam (EB) irradiation showed a significant interaction in all cases (p-value > 0.05), indicating that the effects potentially exerted by ST depended on EB dose and vice-versa. Considering the individual effect of each factor, EB induced more changes than ST, which in fact had a significant effect only for protein and carbohydrates. Among different EB doses, despite the significant differences, it is evident that the nutritional profiles were not greatly changed with any applied dose. Therefore, up to 5 kGy, EB seems to be a suitable conservation treatment for A. bisporus Portobello.
- «
- 1 (current)
- 2
- 3
- »