Análise de falhas em rolamentos por análise de vibração aplicado a aerogeradores

With the heavy use of bearings in various segments of the industry, there are a large number of necessary interruptions in industrial processes to perform maintenance on these devices, with the case study wind turbines. The growth of the wind energy sector, encouraged to conduct research that helps to solve this problem. To contribute to predictive maintenance has been carried out a signal analysis using techniques which allow detection and location of the problem in order to prevent accidents caused and losses due to unexpected equipment failures, whereas low system rotation complicates the detection of the failure. To work around this problem, there was the indication of standard signals for defects in the bearings, making diagnosis of possible failures. With this diagnosis can be performed predictive maintenance, identifying the failure of the system that were tested, such as the introduction of grains of sand in the bearing, wear on the outer race of the bearing and bearing rust. By processing signals it is possible to construct graphs developing a mapping of defects by different peaks in the frequency band.

Modelagem da degradação de fenol em efluentes aquosos através do processo de foto-fenton

Advanced Oxidation Processes (AOP) are techniques involving the formation of hydroxyl radical (HO•) with high organic matter oxidation rate. These processes application in industry have been increasing due to their capacity of degrading recalcitrant substances that cannot be completely removed by traditional processes of effluent treatment. In the present work, phenol degrading by photo-Fenton process based on addition of H2O2, Fe2+ and luminous radiation was studied. An experimental design was developed to analyze the effect of phenol, H2O2 and Fe2+ concentration on the fraction of total organic carbon (TOC) degraded. The experiments were performed in a batch photochemical parabolic reactor with 1.5 L of capacity. Samples of the reactional medium were collected at different reaction times and analyzed in a TOC measurement instrument from Shimadzu (TOC-VWP). The results showed a negative effect of phenol concentration and a positive effect of the two other variables in the TOC degraded fraction. A statistical analysis of the experimental design showed that the hydrogen peroxide concentration was the most influent variable in the TOC degraded fraction at 45 minutes and generated a model with R² = 0.82, which predicted the experimental data with low precision. The Visual Basic for Application (VBA) tool was used to generate a neural networks model and a photochemical database. The aforementioned model presented R² = 0.96 and precisely predicted the response data used for testing. The results found indicate the possible application of the developed tool for industry, mainly for its simplicity, low cost and easy access to the program.

Modelagem da degradação de fenol em efluentes aquosos através do processo de foto-fenton

Advanced Oxidation Processes (AOP) are techniques involving the formation of hydroxyl radical (HO•) with high organic matter oxidation rate. These processes application in industry have been increasing due to their capacity of degrading recalcitrant substances that cannot be completely removed by traditional processes of effluent treatment. In the present work, phenol degrading by photo-Fenton process based on addition of H2O2, Fe2+ and luminous radiation was studied. An experimental design was developed to analyze the effect of phenol, H2O2 and Fe2+ concentration on the fraction of total organic carbon (TOC) degraded. The experiments were performed in a batch photochemical parabolic reactor with 1.5 L of capacity. Samples of the reactional medium were collected at different reaction times and analyzed in a TOC measurement instrument from Shimadzu (TOC-VWP). The results showed a negative effect of phenol concentration and a positive effect of the two other variables in the TOC degraded fraction. A statistical analysis of the experimental design showed that the hydrogen peroxide concentration was the most influent variable in the TOC degraded fraction at 45 minutes and generated a model with R² = 0.82, which predicted the experimental data with low precision. The Visual Basic for Application (VBA) tool was used to generate a neural networks model and a photochemical database. The aforementioned model presented R² = 0.96 and precisely predicted the response data used for testing. The results found indicate the possible application of the developed tool for industry, mainly for its simplicity, low cost and easy access to the program.

Degradação de paracetamol empregando tecnologia oxidativa avançada baseada em fotocatálise heterogênea usando irradiação artificial e solar

In this work, the oxidation and mineralization of paracetamol, based in an advanced oxidative process promoted by heterogeneous photocatalysis, was evaluated. The action of two photocatalysts (titanium dioxide, and a composite based on the association between titanium dioxide and zinc phthalocyanine dye) was studied. First of all, experiments in laboratory scale were performed using as radiation font a 400 W high pressure mercury lamp. The mineralization of paracetamol, promoted by both photocatalysts, was evaluated working with 4L of solution containing 10 mg L-1 of paracetamol and 100 mg L-1 of photocatalyst. To find the best experimental conditions, the influence of hydrogen peroxide concentration and pH was evaluated for the reactions. The best results for the reactions in laboratory scale was obtained using 33,00 mg L-1 of hydrogen peroxide in natural pH (6,80). Under these conditions, 100% oxidation was reached in just 40 minutes of reaction using TiO2 P25, while the mineralization was 78%. Using the composite, the mineralization was 63% in 2 hours of reaction and a oxidation of almost 100% was reached after 60 minutes. A CPC reactor (compound parabolic concentrator) was employed in the expanded work scale, using the sun as irradiation source. In this case the experiments were performed using 50 L of aqueous solution containing 10 mg L-1 of paracetamol and 100 mg L-1 of photocatalyst. The assays were done at pH 3,00 and natural pH (6,80). The used concentration of hydrogen peroxide was 33,00 mg L-1, adopted after laboratory scale studies. The reaction at pH 3,00 shows to be more advantageous, since under natural pH (6,80), the use of deionized water was necessary to prepare the solutions, probably because the deleterious action of carbonate ions, known hydroxyl radical scavengers. Using solar irradiation, the reaction mediated by the composite was more efficient when compared with the assays under laboratory scale since the composite presents the advantage of promoting a better use of visible radiation. Under these conditions, the mineralization increased from 40% to 56% under pH 3,00. At natural pH the oxidation occurred more slowly and the mineralization decreased from 56% to 50%. Thus, the use of pH 3,00 will be more interesting in real scale applications, even if it is necessary the pH correction before the discard of the treated effluent to the environment.

Estudo fitoquímico e biológico das folhas de Banisteriopsis argyrophylla (A. Juss.) B. Gates (Malpighiaceae)

With the increasing fungi resistance compared with existing drugs on the market and the side effects reported by some compounds with antioxidant properties and enzymatic inhibitors, in particular against α-amylase and α-glucosidase, the discovery of new compounds with biological potential, becomes a need. In this context, natural products can be an important source for the discovery of new active molecular architectures. Then, this study aimed to evaluate the antioxidant activity, the enzymatic inhibitory activity of α-amylase and α-glucosidase, the antifungal and cytotoxic activities of ethanolic extract (EE) the leaves of Banisteriopsis argyrophylla (Malpighiaceae) and their fractions, obtained by liquid-liquid extraction using solvents of increasing polarity. The antioxidant activity was evaluated by the free radical DPPH scavenging method (2,2-diphenyl-1-picrylhydrazyl) and the ethyl acetate fractions (FAE) and n-butanol (FB) were the most active, confirmed by the peak current and the oxidation potential obtained by differential pulse voltammetry (DPV). The inhibitory activity of the α-amylase and α-glucosidase was analyzed considering the reactions between substrates α-(2-chloro-4-nitrophenyl)-β-1,4-galactopiranosilmaltoside (Gal-α-G2-CNP) and 4-nitrophenyl-α-D-glucopyranoside (p-NPG), respectively. Initially, it was found that the EE showed considerable activity against α-amylase (EC50 = 2.89±0.1 μg m L–1) compared to the acarbose used as positive control (EC50 = 0.08±0.1 μg mL–1) and that did not showed promising activity against the α-glucosidase. After this observation we evaluated the inhibitory activity of α-amylase fractions, with FAE (EC50 = 2.33±0.1 μg mL–1) and FB (EC50 = 2.57 ± 0.1 μg mL–1) showing the best inhibitions. The antifungal activity was evaluated against Candida species, and the FAE had better antifungal potential (MIC's between 93.75 and 11.72 μg mL–1) compared with amphotericin as positive standard (MIC = 1.00 and 2.00 μg L–1 for C. parapsilosis and C. krusei used as controls, respectively). The EE (CC50 = 360.00 ± 12 μg mL–1) and fractions (CC50's> 270.00 μg mL–1) were considerably less toxic to Vero cells than the cisplatin used as positive control (CC50 = 7.01 ± 0 6 μg mL–1). The FAE showed the best results for the activities studied, this fraction was submitted to ultra performance liquid chromatography coupled with mass spectrometry (UPLC-MS)), and the following flavonoids have been identified: (±)-catechin, quercetin-3-O-β-D-Glc/ quercetin-3-O-β-D-Gal, quercetin-3-O-β-L-Ara, quercetin-3-O-β-D-Xyl, quercetin-3-O-α-L-Rha, kaempferol-3-O-α-L-Rha, quercetin-3-O-(2''-galoil)-α-L-Rha, quercetin-3-O-(3''-galoil)-α-L-Rha and kaempferol-3-O-(3''-galoil)-α-L-Rha,. FAE was submitted to column chromatography using C18 phase, and (±)-catechin was isolated (FAE-A1, 73 mg) and three fractions consisting of a mixture of flavonoids were obtained (FAE-A2, FAE-A3 and FAE-A4). These compounds were identified by thin layer chromatography (TLC) and (–)-ESI-MS. The (±)-catechin fraction showed an MIC = 2.83 μg ml–1 in assay using C. glabrata, with amphotericin as positive control. The fractions FAE-A2, FAE-A3, FAE-A4, showed less antifungal potential in tested concentrations. The identified flavonoids are described in the literature, regarding their antioxidant capacity and (±)-catechin, quercetin-3-O-Rha and kaempferol-3-O-Rha are described as α-amylase inhibitors. Thus, B. argyrophylla is an important species that produces compounds with antioxidant potential that can be related to the traditional use as anti-inflammatory and also has antifungal compounds and inhibitors of α-amylase. Therefore, these leaves are promising resources for the production of new drugs.

Avaliação da estabilidade físico-química de óleo alimentar suplementado com extrato de carqueja

A prevenção da oxidação lipídica, uma das principais causas de degradação de óleos alimentares, pode ser efetuada pela adição de antioxidantes. A preocupação pelo consumo de alimentos mais saudáveis e isentos de aditivos sintéticos tem contribuído para a crescente procura de antioxidantes naturais provenientes de plantas, que possam substituir os antioxidantes sintéticos em óleos e gorduras alimentares. O presente estudo teve como objetivo avaliar o efeito da adição de extrato de carqueja (Pterospartum tridentatum), em concentrações diferentes (500 mg/kg e 1000 mg/kg), na estabilidade físico-química de óleo alimentar submetido a três ciclos de aquecimento (9 horas cada) a 180ºC e de óleo armazenado à temperatura ambiente durante 30 dias. O extrato de carqueja foi obtido por extração em etanol, tendo-se alcançado um rendimento de 60,2%±0,225. Determinou-se a capacidade antioxidante do extrato de carqueja por avaliação da capacidade de redução do radical 1,1-difenil-2-picrilhidrazil (DPPH) e pelo método de Folin-Ciocalteu. Os resultados demonstraram que o extrato tem uma atividade antioxidante de 61,7%±0,38 e um teor de compostos fenólicos de 22,4 mg de equivalentes de ácido gálico /g de extrato. A estabilidade físico-química do óleo alimentar foi estudada através da análise de diversos parâmetros, nomeadamente acidez, índice de peróxidos, índice de p-anisidina, absorvância no UV, índice de refração, cor e densidade. Os resultados evidenciaram um aumento de todos os parâmetros, com exceção da cor, ao longo do aquecimento do óleo bem como no seu armazenamento à temperatura ambiente. Este aumento foi mais relevante no óleo em processo de aquecimento uma vez que a 180ºC as reações de oxidação ocorrem mais rapidamente do que à temperatura ambiente. Observaram-se alterações mais acentuadas dos parâmetros físico-químicos no óleo sem extrato de carqueja comparativamente ao óleo suplementado com 500mg/kg e 1000mg/kg de extrato, comprovando-se o efeito do extrato de carqueja na redução da oxidação e, consequentemente, no aumento da estabilidade físico-química do óleo alimentar. O óleo suplementado com 1000mg/kg de extrato de carqueja revelou-se o mais estável à oxidação.

Melhoria do processo de lavação das rolhas de cortiça

O presente trabalho, realizado na empresa Amorim & Irmãos, S.A. teve como principal objetivo a avaliação e otimização da lavação de rolhas de cortiça técnicas, designadas por Twin Top®, em termos do perfil de consumo de reagentes químicos e do desenvolvimento da sua brancura. Para tal foi desenvolvida uma metodologia de análise de brancura de rolhas Twin Top® que serviu de base para a determinação de uma gama de brancuras aceitável. Para além disto, efetuou-se a avaliação do processo de lavação atualmente praticado e apartir do qual se realizaram os ensaios de otimização a nível laboratorial e piloto. Foram aplicados diferentes métodos de análise tais como, UV-Vis, FTIR-ATR, RMN e brancura ISO. Tendo como base de análise os espetros de refletância difusa de espetroscopia de UV-Vis foi proposta uma metodologia de determinação da brancura de rolhas Twin Top® a 457nm, adoptando as condições da Norma ISO 3688, aplicada na indústria da pasta e papel. De seguida, aplicando o método anteriormente definido, analisaram-se 1000 rolhas Twin Top® de lavação branca. Sendo que os resultados demonstraram que para rolhas dentro de especificação a brancura ISO deve estar entre os 30 e 35%. Foram ainda analisadas rolhas de diferentes classes visuais e provenientes de várias máquinas de lavação da fábrica para determinar possíveis diferenças. Para proceder à avaliação da lavação existente analisaram-se as colas usadas na produção das rolhas, um grânulo de cortiça e a matéria seca do efluente de lavação por FTIR-ATR e RMN. Desta avaliação resultou a presença de compostos de cortiça e cola degradada no efluente de lavação. Determinou-se a concentração dos reagentes intervenientes no processo que se mostraram de acordo com as especificações indicadas pelos fornecedores. Para a otimização da lavação combinou-se o peróxido de hidrogénio e hidróxido de sódio em diferentes quantidades, concentrações e diferentes tempos de reação o que permitiu identificar a melhor alternativa à lavação convencional. Assim existem duas propostas que devem ser tidas em consideração: uma em que a lavação mantém a mesma sequência da convencional e em que se altera o local de adição dos reagentes, que deve ser o mais próxima e direta possível das rolhas, e a outra em que se reduz o tempo do processo em 29,3 min, que compreende apenas uma oxidação e em que a quantidade de reagentes aplicada corresponde à soma dos volumes de reagentes das três oxidações do processo convencional.

Aproveitamento de subprodutos da indústria de carne suína: caracterização físico-química do queijo de porco

Headcheese is a meat sausage originated from Europe made from hog slaughter by-products. It is a much appreciated product in the South of Brazil which is increasingly established in the market, however it does not have official regulations yet. This study aimed to present the physicochemical characterization of headcheese in a western Santa Catarina industry supervised by Companhia Integrada de Desenvolvimento Agrícola de Santa Catarina and assess 10 different brands to find the relationship between chemical composition and texture profile analysis (TPA). Thus, the chemical composition, energy value, total nitrite, lipid oxidation and physical parameters (color and texture) were evaluated. The product exhibited great variability in moisture content, lipid and protein because the different formulations, processing and intrinsic and extrinsic characteristics of raw material. The utilization of offal provided higher cholesterol and iron levels, and the high content of collagen was accountable for the shear force responses (7.84 ± 1.68 N). The product showed higher amount of sodium, due to the use of additives, but calcium levels were compatible with other sausages. There was a predominance of polyunsaturated fatty acids and polyunsaturated fatty acids/saturated fatty acids ratio was more favorable than other sausage in the same category. Nitrite assured preservation effects and thus lower product levels of oxidation were observed. The high Water Activity and pH 6.5 showed that the product is susceptible to growth of pathogens and requires cooling for preservation. Its brownish occurred due to cooking and production of metmyoglobin. There was a strong positive correlation between collagen and attributes of TPA, especially for chewiness (r = 0.855). The use of Hierarchical Cluster Analysis and Principal Component Analysis were able to separate three groups based on the amount of collagen and texture attributes, especially hardness, gumminess and chewiness.

Melhoria da qualidade de jerked beef pela substituição de nitrito de sódio por extratos naturais de própolis e erva mate como agente antioxidante

Jerked beef, an industrial meat product obtained from beef with the addition of sodium chloride and curing salts and subjected to a maturing and drying process is a typical Brazilian product which has been gradually discovered by the consumer. The replacement of synthetic antioxidants by natural substances with antioxidant potential due to possible side effects discovered by lab tests, consumer health, is being implemented by the meat industry. This study aimed to evaluate the lipid oxidation of jerked beef throughout the storage period by replacing the sodium nitrite by natural extracts of propolis and Yerba Mate. For jerked beef processing brisket was used as raw material processed in 6 different formulations: formulation 1 (control - in nature), formulation 2 (sodium nitrite - NO), formulation 3 (Yerba Mate - EM), formulation 4 (propolis extract - PRO), formulation 5 (sodium nitrite + Yerba Mate - MS + NO), formulation 6 (propolis extract + sodium nitrite - PRO + NO). The raw material was subjected to wet salting, dry salting (tombos), drying at 25°C, packaging and storage in BOD 25°C. Samples of each formulation were taken every 7 days for analysis of lipid oxidation by the TBARS method. In all formulations, were carried out analysis of chemical composition at time zero and sixty days of storage. The water activity analysis and color (L *, a *, b *) was monitored at time zero, thirty and sixty days of storage. The Salmonella spp count, Coliform bacteria, Termotolerant coliforms and coagulase positive staphylococci were taken at time zero and sixty days. The activity of natural antioxidants evaluated shows the decline of lipid oxidation up to 2.5 times compared with the product in natura and presented values with no significant differences between treatments NO and EM, confirming the potential in minimize lipid oxidation of Jerked beef throughout the 60 days of storage. The results also showed that yerba mate has a higher antioxidant capacity compared to the propolis except the PRO + NO formulation. When associated with yerba mate with sodium nitrate, TBARS values become close to values obtained only for the control samples with the addition of sodium nitrite. The proximal composition of the formulations remained within the standards required in the IN nº22/2000 for jerked beef. Samples that differ significantly at 5% are directly related to the established type of formulation. The count of microorganisms was within the standards of the DRC nº12/2001 required for matured meat products. The intensity of the red (a*) decreased with storage time and increase the intensity of yellow (b*) indicates a darkening of the product despite L* also have been increased. These results suggest that yerba mate is a good alternative to meat industry in reducing healing addition salts when associated with another antioxidant.

Coupling of magnetic, strain and electric polarization fields in the structure of multiferroic material

The comprehensive study on the coupling of magnetism, electrical polarization and the crystalline lattice with the off-stoichiometric effects in self-doped multiferroic hexagonal h-LuMnxO3±δ (0.92≤x≤1.12) ceramic oxides was carried out for the PhD work. There is a complex coupling of the three ferroic degrees. The cancelation of the magnetic moments of ions in the antiferromagnetic order, electric polarization with specific vortex/antivortex topology and lattice properties have pushed researchers to find out ways to disclose the underlying physics and chemistry of magneto-electric and magneto-elastic couplings of h-RMnO3 multiferroic materials. In this research work, self-doping of Lu-sites or Mn-sites of h-LuMnxO3±δ ceramics prepared via solid state route was done to pave a way for deeper understanding of the antiferromagnetic transition, the weak ferromagnetism often reported in the same crystalline lattices and the ferroelectric properties coupled to the imposed lattice changes. Accordingly to the aim of the PhD thesis, the objectives set for the sintering study in the first chapter on experimental results were two. First, study of sintering off-stoichiometric samples within conditions reported in the bibliography and also extracted from the phase diagrams of the LuMnxO3±δ, with a multiple firings ending with a last high temperature step at 1300ºC for 24 hours. Second, explore longer annealing times of up to 240 hours at the fixed temperature of 1300 ºC in a search for improving the properties of the solid solution under study. All series of LuMnxO3±δ ceramics for each annealing time were characterized to tentatively build a framework enabling comparison of measured properties with results of others available in literature. XRD and Rietveld refinement of data give the evolution the lattice parameters as a function to x. Shrinkage of the lattice parameters with increasing x values was observed, the stability limit of the solid solution being determined by analysis of lattice parameters. The evolution of grain size and presence of secondary phases have been investigated by means of TEM, SEM, EDS and EBSD techniques. The dependencies of grain growth and regression of secondary phases on composition x and time were further characterized. Magnetic susceptibility of samples and magnetic irreversibility were extensively examined in the present work. The dependency of magnetic susceptibility, Neel ordering transition and important magnetic parameters are determined and compared to observation in other multiferroics in the following chapter of the thesis. As a tool of high sensitivity to detect minor traces of the secondary phase hausmannite, magnetic measurements are suggested for cross-checking of phase diagrams. Difficulty of previous studies on interpreting the magnetic anomaly below 43 K in h-RMnO3 oxides was discussed and assigned to the Mn3O4 phase, with supported of the electron microscopy. Magneto-electric coupling where AFM ordering is coupled to dielectric polarization is investigated as a function of x and of sintering condition via frequency and temperature dependent complex dielectric constant measurements in the final chapter of the thesis. Within the limits of solid solubility, the crystalline lattice of off-stoichiometric ceramics was shown to preserve the magneto-electric coupling at TN. It represents the first research work on magneto-electric coupling modified by vacancy doping to author’s knowledge. Studied lattices would reveal distortions at the atomic scale imposed by local changes of x dependent on sintering conditions which were widely inspected by using TEM/STEM methods, complemented with EDS and EELS spectroscopy all together to provide comprehensive information on cross coupling of distortions, inhomogeneity and electronic structure assembled and discussed in a specific chapter. Internal interfaces inside crystalline grains were examined. Qualitative explanations of the measured magnetic and ferroelectric properties were established in relation to observed nanoscale features of h-LuMnxO3±δ ceramics. Ferroelectric domains and topological defects are displayed both in TEM and AFM/PFM images, the later technique being used to look at size, distribution and switching of ferroelectric domains influenced by vacancy doping at the micron scale bridging to complementary TEM studies on the atomic structure of ferroelectric domains. In support to experimental study, DFT simulations using Wien2K code have been carried out in order to interpret the results of EELS spectra of O K-edge and to obtain information on the cation hybridization to oxygen ions. The L3,2 edges of Mn is used to access the oxidation state of the Mn ions inside crystalline grains. In addition, rehybridization driven ferroelectricity is also evaluated by comparing the partial density of states of the orbitals of all ions of the samples, also the polarization was calculated and correlated to the off-stoichiometric effect.

Antioxidant and detoxify genes polymorphisms in colorectal cancer predisposition

Colorectal cancer (CRC) results from histologic and gene alterations can lead to a massive cellular proliferation. Most of the authors assume multifactorial causes to CRC genesis. Low physical activity, a fat diet poor in fibers and smoking habits seems to have an important role in CRC. However, there are also genetic causes associated with CRC risk. It has been described that oxidative stress levels could influence CRC development. Thus, cellular balance reactive species and defense enzymes involved in oxidative stress are crucial to maintain a good tissue function and avoid neoplasic process. Therefore, genome variations on these defense enzymes, such as MNSOD, SOD3, GSTP1, GSTT1 and GSTM1, could be important biomarkers to colorectal adenocarcinomas. We intend to determine frequencies distribution of most common polymorphisms involved on oxidative stress regulation (MNSOD, SOD3, GSTP1, GSTT1 and GSTM1) in patients with sporadic colorectal adenocarcinoma (SCA) and in healthy controls, evaluation their possible correlation with SCA risk. Samples common polymorphisms of antioxidant and detoxify genes (MNSOD T175C, SOD3 R213G, GSTP1 A105G, GSTP1 C114T, GSTT1del and GSTM1del) analysis was done by PCR-SSP techniques. In this study we found a higher prevalence of MNSOD 175CC (55% vs 2%; p<0.0001; OR: 58.5; CI 13.3 to 256.7), SOD3 213GG (31% vs 2%; p<0.0001; OR: 21.89; CI 4.93 to 97.29), GSTP1 105GG (46% vs 12%; p<0.0001; OR: 6.14; CI 2.85 to 13.26), GSTP1 114TT (38% vs 0%; p<0.0001; OR: Infinity) and GSTT1 null (75% vs 28%; p<0.0001; OR: 7.71; CI 3.83 to 15.56) mutated genotypes among SCA patients, while the normal genotypes were associated with SCA absence. Furthermore, we found GSTP1 114TT mutated genotype (52% vs 27%; p=0.003; OR: 2.88; CI: 1.41 to 5.89) and GSTT1 null genotype (87% vs 65%; p=0.003; OR: 3.66; CI 1.51 to 8.84) associated with colon samples. These findings suggest a positive association between most of common polymorphisms involved on oxidative stress regulation and SCA prevalence. Dysregulation of MNSOD, SOD3, GSTP1, GSTT1 and GSTM1 genes could be associated with an increase of ROS in colon and rectum tissue and p53 pathway deregulation, induced by oxidative stress on colonic and rectal cells. The present study also provides preliminary evidence that MNSOD 175C, SOD3 213G, GSTP1 105G, GSTP1 114T and GSTT1 null polymorphisms, may be involved in SCA risk and could be useful to clarify this multifactorial disorder.

Elaboração de paté de lapa, Patella spp. com adição de medronho, Arbutus unedo: caraterização físico-química, microbiológica e sensorial e avaliação da estabilidade oxidativa

As lapas do género Patella são moluscos gastrópodes em crescente utilização na alimentação humana, sendo um petisco muito apreciado em várias regiões costeiras de Portugal. De acordo com a fileira do pescado, o consumo de produtos da pesca ricos em ácidos gordos polinsaturados têm vindo a substituir os produtos de origem animal terrestre através dos produtos filetados, reestruturados e pré-cozinhados. A oxidação dos alimentos é a causa mais importante na deterioração da qualidade nutricional e sensorial dos produtos da pesca. Assim nos últimos anos, tem-se verificado um interesse crescente na utilização de antioxidantes naturais de origem vegetal (frutas e vegetais) em detrimento de antioxidantes sintéticos, aquando da elaboração de produtos reestruturados de origem animal (hambúrgueres, salsichas e patés). Para além deste efeito antioxidante, existe uma relação benéfica entre o consumo de frutas e vegetais, ricos em compostos fenólicos e a prevenção de certas doenças. Este trabalho pretende produzir e caracterizar ao nível físico-químico, sensorial e microbiológico um paté elaborado a partir de lapas, com adição do fruto silvestre medronho, bem como a valorização destas matérias-primas ao proporcionar uma mais-valia nutricional/funcional e económica com o desenvolvimento de um produto inovador (paté). Por outro lado, avaliou-se a estabilidade oxidativa do paté em armazenamento refrigerado durante 90 dias bem como a aceitabilidade do mesmo. Sendo assim, produziram-se três tipos de patés inovadores: i) paté de lapa com BHT (PCON), ii) paté de lapa com 3% de medronho (PAU3) e iii) paté de lapa com 6% de medronho (PAU6). Os resultados da avaliação da estabilidade oxidativa (PAU6>PAU3>PCON) confirmam a elevada capacidade do extrato de medronho rico em compostos fenólicos como inibidor eficaz na oxidação lipídica do paté de lapa e com boa aceitação sensorial.

Propriedades electroquímicas dos sesquióxidos com estrutura cúbica tipo-C

Doutoramento em Ciência e Engenharia dos Materiais

Comparação da medida de cor de pescado entre sistema de visão computacional e colorímetro convencional no frescor do pescado

A cor da superfície dos alimentos é o primeiro parâmetro de qualidade avaliado pelos consumidores, e é critico para a aceitação do produto, então a medição adequada da cor é uma importante ferramenta. Nesta pesquisa avaliou-se a variação da cor em corvina (Micropogonias furnieri) armazenada em gelo durante 16 dias; os parâmetros de luminosidade (L*), valor cromático a*, valor cromático b*, variação total da cor (ΔE) e croma (C*) foram obtidos por sistema de visão computacional, e por colorímetro Konica Minolta CR-400. O frescor da corvina baseada nas mudanças da cor das brânquias foi avaliado utilizando um sistema de visão computacional. Também se modelou a oxidação da mioglobina em files de burriquete (Pogonias cromis), utilizando os parâmetros de vermelho (valor a* e R). Para registrar as mudanças da cor durante 57,6 h utilizou-se um sistema de visão computacional, a análise química realizou-se determinando a concentração de metamioglobina (%). Na avaliação da cor de corvina armazenada em gelo, o sistema de visão computacional mostrou diferenças significativas para L*, a*, ΔE e C*, enquanto que o colorímetro mostrou diferenças significativas para L* e ΔE, o único parâmetro que não apresentou diferenças entre instrumentos foi ΔE durante a avaliação da corvina armazenada em gelo. O coeficiente de correlação entre os parâmetros da cor (L*, a* e b*) das brânquias da corvina armazenada em gelo pelo tempo de armazenamento foi de 0,9747. O sistema de visão computacional registrou as mudanças da cor em filés de burriquete e se modelaram as mudanças utilizando um modelo exponencial. O sistema de visão computacional mostrou ser mais sensível às mudanças da cor durante a avaliação da cor na corvina armazenada em gelo. É possível prognosticar o tempo de armazenamento da corvina em gelo em função da mudança da cor das brânquias. Assim, foi possível modelar a variação da mioglobina em filés de burriquete utilizando sistemas de visão computacional para registrar ditas mudanças. Os sistemas de visão computacional têm grande capacidade para registrar as mudanças da cor e é possível utiliza-los para avaliar os alimentos em função da cor.

Processos Oxidativos Avançados para Remediação de Águas Contaminadas por Pesticidas

Este trabalho teve como objectivo inicial o estudo de processos oxidativos avançados de forma a remediar e tratar águas contaminadas por pesticidas. No entanto, ao longo do trabalho experimental, constatou-se que os produtos resultantes da degradação de pesticidas são muitas vezes mais tóxicos do que os compostos que lhes deram origem e que, por isso, degradar um composto nem sempre é o melhor para o ambiente. Assim, neste trabalho, procurou-se estudar o processo de degradação com o objectivo de minimizar o impacto ambiental dos pesticidas na água e no ambiente em geral. A parte experimental deste trabalho foi dividida em duas etapas, sendo que, em ambas, a voltametria de onda quadrada e a espectrofotometria de UV/Vis foram os métodos de análise utilizados, para acompanhar o processo de fotodegradação. Na primeira etapa estudou-se a relação entre a estrutura química dos pesticidas MCPA, MCPP, 2.4-D e Dicloroprop e a sua fotodegradação. Soluções aquosas dos pesticidas enunciados foram submetidas a irradiação UV/vis, com incrementos variáveis de tempo de irradiação. Os resultados obtidos, nesta etapa, permitiram constatar diferenças na percentagem de degradação dos diferentes pesticidas. Dos pesticidas estudados verificou-se uma maior fotodegradação para o MCPA e MCPP seguido do Dicloroprop e finalmente o 2.4-D que se degradou menos. Os dados obtidos sugerem que a fotodegradação destes pesticidas está intimamente ligada com a estrutura das moléculas. A presença de um maior número de grupos cloro ligados ao anel aromático nos pesticidas 2,4-D e Dicloroprop faz com que estes sejam mais estáveis e por isso se degradam menos que o MCPA e o MCPP. Por outro lado, o facto de o 2,4-D apresentar um potencial de oxidação mais elevado do que o Dicloroprop, faz com que este seja mais difícil de degradar, o que justifica a diferença entre os dois. Desta forma, foi possível concluir que a estrutura dos pesticidas condiciona o processo de degradação, como esperado. Na segunda etapa, estudou-se a estabilização dos pesticidas MCPA e MCPP após encapsulação, com 2-hidroxipropil-β-ciclodextrina (HP-β-CD), em água desionizada e em água do rio. Para tal, submeteram-se as soluções aquosas dos pesticidas com e sem ciclodextrina, a irradiação UV/vis, também com incrementos variáveis de tempo. No caso do MCPA verificou-se que, tanto para água desionizada como para água do rio, que este herbicida encapsulado se degrada bastante menos do que o MCPA livre. O encapsulamento permitiu reduzir quase para metade a taxa de fotodegradação. Assim, confirmou-se que a HP-β-CD permite estabilizar este pesticida, tornando-o mais resistente à fotodegradação. Desta forma, originam-se menos produtos de degradação, os quais podem ser mais tóxicos, e reduz-se de o impacto ambiental deste herbicida. Verificou-se também que o MCPA livre se degrada mais em água do rio do que em água desionizada, provavelmente devido à matéria orgânica presente nesta água, que promove o processo de degradação. No que respeita ao MCPP também se constatou que este herbicida se degrada menos encapsulado do que livre, em água desionizada e em água do rio. Neste caso, conseguiu-se reduzir pouco a taxa de fotodegradação, mas, ainda assim se verifica uma estabilização deste pesticida através do encapsulamento. No entanto, tornou-se mais evidente a estabilização do MCPP após encapsulação em água do rio, já que apresenta uma taxa de fotodegradação menor. Este facto demonstra que a HP-β-CD permite estabilizar também este pesticida, tornando-o mais resistente à fotodegradação, e reduzindo seu impacto ambiental.