Structural and magnetic properties of CoFe2O4 thin films deposited by laser ablation on Si (001) substrates

Cobalt ferrite (CoFe(2)O(4)) thin films have been deposited on Si (001) substrates, with different substrate ternperatures (Td,p = 25 degrees C - 600 degrees C). The films were prepared by pulsed laser ablation with a KrF excimer laser (wavelength lambda = 248 nm). The oxygen pressure during deposition was 2 x 10(-2) mbar. The films structure was studied by X-ray diffraction (XRD) and their surface was examined by scanning electron microscopy (SEM). The magnetic properties were measured with a vibrating sample magnetometer (VSM). For low deposition temperatures, the films presented a mixture ofa CoFe(2)O(4) phase, with the cubic spinel structure, and cobalt and iron antiferromagnet oxides with CoO and FeO stoichiometries. As the deposition temperature increased, the CoO and FeO relative content strongly decreased, so that for Tdep = 600 degrees C the films were composed mainly by polycrystalline CoFe(2)O(4). The magnetic hysteresis cycles measured in the films were horizontally shifted due to an exchange coupling field (H(exch)) originated by the presence of the antiferromagnetic phases. The exchange field decreased with increasing deposition temperature, and was accompanied by a corresponding increase of the coercivity and remanence ratio of the cycles. This behavior was due to the strong reduction of the CoO and FeO content, and to the corresponding dominance of the CoFe(2)O(4) phase on the magnetic properties of the thin films.This work has been financially supported by the Portuguese Foundation for Science and Technology (FCT), through the project POCI/CTM/60181/2004

Atividade enzimática de leveduras isoladas na fase final de fermentação natural de azeitonas de mesa da região de Trás-os-Montes

Projeto SUB-IOC-TEC 11/12 “Table olives from the northeast of Portugal: Contribution for their characterization and promotion”As leveduras estão activamente envolvidas no processo de fermentação da azeitona produzindo compostos com atributos organolépticos importantes e que são fundamentais na qualidade e sabor do produto final. A título de exemplo refere-se a associação de algumas espécies à hidrólise da oleuropeina catalisada pela enzima β– glucosidase. A dominância de leveduras na fase final de fermentação de azeitonas de mesa pode ser explicada pela sua tolerância aos compostos fenólicos e às concentrações de NaCl usadas no processamento de azeitona. O presente trabalho pretendeu avaliar a atividade enzimática de diferentes isolados de leveduras obtidas na fase final de fermentação natural de azeitonas de mesa, da região de Trás-os-Montes. As amostras obtidas de três produtores artesanais foram subdivididas em duas subamostras (salmoura e azeitonas) e os isolados foram identificadas por sequenciação da região D1-D2 do gene 26S rDNA. Posteriormente foi efetuado o screening dos isolados de leveduras através de métodos qualitativos para a presença das enzimas catalase, β-glucosidase, protease, amílase e lípases. No seu conjunto foram identificadas sete espécies de leveduras, nomeadamente Candida ishiwadae, C. boidinii, Pichia membranifaciens, P. manshurica, Saccharomyces paradoxus, Sporobolomyces roseus e Wickerhamomyces anomalus. As espécies C. ishiwadae, W. anomalus e P. manshurica, estiveram presentes nos dois substractos, S. paradoxus apenas foi observada na polpa, enquanto as restantes ocorreram na salmoura. A atividade da catalase foi observada em todas as espécies isoladas. Candida ishiwadae e W. anomalus apresentaram capacidade de produzir β-glucosidase e proteases, tendo sido também detetada a produção de amilases por W. anomalus. Das espécies avaliadas, S. roseus foi aquela que apresentou maior potencial biotecnológico, visto produzir todas as enzimas testadas. Porém, para uma melhor caraterização destes isolados serão ainda necessários testes adicionais que possibilitarão avaliar inequivocamente as propriedades tecnológicas destas leveduras

Qualidade microbiológica de azeitonas de mesa provenientes de produtores artesanais de Trás-os-Montes

As azeitonas de mesa são um alimento importante da dieta Mediterrânica, e devido à sua composição química, um elevado teor em compostos fenólicos, algumas vitaminas e uma gordura maioritariamente monoinsaturada, são-lhe atríbuidos diferentes benefícios para a saúde. Em Portugal, a elaboração de azeitonas de mesa tem uma larga tradição, sobretudo nas regiões do interior, onde Trás-os-Montes se insere, representando uma fonte económica importante para os produtores tradicionais. Nestes produtores, as azeitonas são geralmente comercializados a granel e por isso sujeitas a contaminações microbianas, podendo constituir um risco para a saúde dos consumidores. O presente trabalho pretendeu avaliar a qualidade microbiológica de azeitonas de mesa obtida de produtores artesanais da região. Para o efeito, recolheram-se 8 amostras em condições de assepsia de diferentes produtores e avaliaram-se os seguintes parâmetros microbiológicos: microrganismos mesófilos totais, leveduras, coliformes totais, Escherichia coli, Staphylococcus aureus, Salmonella spp. e esporos de clostrídios sulfito redutores. Na polpa de azeitona a população de mesófilos variou de 1×102 a 6×104 e a de leveduras de 2×102 a 6×105 UFC/g; enquanto na salmoura oscilou de 9×102 a 2×105 e de 8×102 a 1×106 UFC/mL, respectivamente. Nenhuma das amostras analisadas revelou a presença de microrganismos indicadores de contaminação fecal, bem como microrganismos patogénicos, como sejam S. aureus e Salmonella spp.. Estes resultados sugerem que as azeitonas de mesa da região de Trás-os-Montes são processadas em boas condições de higiene não apresentando perigos microbiológicos para a segurança do consumidor.Projeto SUB-IOC-TEC 11/12 “Table olives from the northeast of Portugal: Contribution for their characterization and promotion

Volatile compounds contribution of Hanseniaspora guilliermondii and Hanseniaspora uvarum during red wine vinifications

This work aims to investigate the contribution of a selected non-Saccharomyces yeast species, Hanseniaspora guilliermondii, to higher alcohols, esters, fatty acids and heavy sulphur compounds composition of red wine. Red grape must vinifications of 100 l were performed and an inoculated fermentation with H. guilliermondii was compared to a spontaneous fermentation. The presence of apiculate yeasts was observed in both fermentations; however, Hanseniaspora uvarum was the only apiculate yeast isolated from the spontaneous fermentation. Apiculate yeasts dominated the fermentation until an ethanol concentration of 6% (v/v) was attained and remained in considerable high levels for an ethanol concentration of 12.5% (v/v). The grape must inoculated with H. guilliermondii led to the production of wine with higher concentrations of 1-propanol, 2-phenylethyl acetate and 3-(methylthio)propionic acid, and lower amounts of ethyl hexanoate, pentanoic acid, free fatty acids, 2-methyltetrahydrothiophen-3- one and acetic acid-3-(methylthio)propyl ester, than wine resulting from the spontaneous fermentation. The present study shows that the use of specific apiculate yeasts in grape must fermentations may lead to the production of wines with different chemical profiles, emphasising the importance of Hanseniaspora yeasts as mixed starter cultures with Saccharomyces cerevisiae, in winemaking.info:eu-repo/semantics/acceptedVersio

Thermal environment in two broiler barns during the first three weeks of age

The objective of this research was to evaluate the internal thermal environment of two broiler barns featuring different ventilation systems representative of Brazilian and South American poultry production industry: (a) a negative-pressure tunnel and (b) a positive- pressure lateral ventilation system. Environmental parameters such as dry bulb temperature, relative humidity and temperature-humidity index were assessed; temperature maps for day and night average conditions were determined for the first three weeks of life. Better uniformity of the thermal environment and comfort conditions inside the negative-pressure tunnel were found

A CFD based approach for determination of ammonia concentration profile and flux from poultry houses with natural ventilation

The understanding of concentration and emissions distribution of gases such as ammonia (NH3) in agricultural installations is of growing importance due to its effect on health and productivity of animals and workers. The objective of this study was to use validated Computational Fluid Dynamics (CFD) model as a tool to predict NH3 concentration distribution and mass fluxes in a non-insulated broiler chicken installation with natural ventilation, typically found in subtropical and tropical contries. Results from this study indicated that simulation with CFD can be used to predict NH3 concentration distribution and mass flux inside similar installations with incident winds from different directions of entrance at the lateral opening of the installation. The most direct application of the proposed mode would be to help improving the existing buildings and also to help in the conception of new ones, and may also apply the model to help in the development of NH3 emission inventories

Bread with stoned table olives – the union of two traditional products of excellence of Trás-os-Montes region, Portugal: preliminary results

The aim of the present work was to conduct a preliminary study on characterization of wheat bread with stoned green table olives, also called “alcaparras”, in order to obtain a produce that join two traditional products of excellence from Trás-os-Montes region, Northeast of Portugal. ”Alcaparras” are processed from healthy green or yellow-green olives, which are broken using a wooden hammer separating the pulp of the core. The pulp is sliced into two approximately equal parts perpendicularly to the major axis of the fruit and placed on water, which is changed three to four times during a week. This treatment has the purpose of removing olive bitterness. Afterwards the product is stored in brine until consumption. Wheat breads were prepared with different percentages of ”alcaparras”: 0, 3, 5 and 7% and stored at 25 °C for 4 days, being analysed every two days, regarding pH, ash, fat and salt contents, as well as mesophiles, moulds and yeasts. The physicochemical determinations were only made at 0 and 2 days because after the fourth day the bread had developed moulds. The breads presented pH values between 5.85-5.96, salt 0.51- 1.01% (d.w.–dry weight), ash 2.13-2.77% (d.w.) and fat 2.00-3.78% (d.w.) contents. The breads with the highest ”alcaparras” percentage presented the lowest pH value and the highest salt and ash contents. As expected the breads with the lowest fat content were those without ”alcaparras”. The mesophiles varied between 1.3-7.4 log UFC/g (f.w.), and moulds and yeasts between <1 to 5 log UFC/g (f.w.), being the highest values obtained at the end of storage. In conclusion, bread with ”alcaparras” is a promising product to be sold in gourmet shops; however, more studies are needed to increase its shelf-life. The inclusion of ”alcaparras” in traditional breads is also an innovative strategy to valorise two different food products at once.This work was performed in collaboration with the TRADEIT project which has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement n° 613776.info:eu-repo/semantics/publishedVersio