Análise de compostos bioativos, grupos ácidos e da atividade antioxidante do café arábica (Coffea arabica) do cerrado e de seus grãos defeituosos (PVA) submetidos a diferentes torras

O presente trabalho estudou os compostos bioativos (ácidos clorogênicos, trigonelina, cafeína, fenóis totais e proantocianidinas), grupos hidroxila ácidos e atividade antioxidante de um café arábica proveniente do Cerrado Mineiro e de seu PVA (grãos pretos, verdes e ardidos). As amostras foram preparadas nas torras clara (180 ± 10 °C; 6,0 ± 1,0 minutos), média (180 ± 10 °C; 8,0 ± 1,0 minutos) e escura (180 ± 10 °C; 10,0 ± 1,0 minutos). Considerando-se a média das três torras do café e do PVA, a diferença observada no teor de todos os constituintes acima não foi significativa (p > 0,05), exceto com o teor de grupos hidroxila ácidos que foi ligeiramente superior no PVA e cafeína calculada pelo método semiquantitativo que foi superior no café. Portanto, dentre esses constituintes, os compostos com grupos ácidos seriam os únicos que poderiam contribuir para explicar a grande diferença de sabor existente entre o café de grãos sadios e o de PVA. Tanto o café como o PVA apresentaram atividade seqüestradora do radical DPPH. nas três torras, sendo a atividade do café sempre superior. Analisando-se as variações dos teores de cafeína, fenóis totais, proantocianidinas, grupos hidroxila ácidos, trigonelina e ácidos clorogênicos, não foi possível explicar a atividade antioxidante superior apresentada pelo café da torra média (CE50 de 2,3 mg.mg-1 de DPPH.).

Avaliação cromatográfica de compostos voláteis de cachaças produzidas com leveduras de diferentes procedências

Procurou-se neste trabalho produzir cachaças em escala de laboratório a partir de leveduras isoladas de alambiques de diferentes regiões de Minas Gerais, avaliando-se e comparando-se a composição química destas em relação a cachaças de marcas comerciais. Os alambiques selecionados para isolamento das leveduras produzem tradicionalmente cachaças com características artesanais, cujos procedimentos as diferenciam sensorial e quimicamente das cachaças industriais. Avaliou-se a cinética de algumas das fermentações com relação ao teor alcoólico e à acidez produzidos durante a fermentação e alguns mostos atingiram concentrações de etanol da ordem de 9 ºGL e acidez de 55 mg.100 mL-1. Os compostos avaliados por cromatografia gasosa foram acetaldeído, acetato de etila, metanol, 1-propanol, álcool isobutílico, álcool isoamílico, furfural e ácido acético. As concentrações mais elevadas foram de alcoóis superiores totais, preponderando o álcool isoamílico, e de ácido acético. A composição mostrou-se bastante variável (40,59 a 671,86 mg de ácido acético.100 mL-1 de álcool anidro e 20,68 a 178,6 mg de acetaldeído.100 mL-1 de álcool anidro), e foi contrastada com os limites legais estabelecidos pela legislação brasileira (Instrução Normativa nº 13, de 30/06/2005, do Ministério da Agricultura, Pecuária e Abastecimento).

Intensidade de pigmentação vermelha em maçãs e sua relação com os teores de compostos fenólicos e capacidade antioxidativa

Os compostos fenólicos influenciam a qualidade de maçãs e seus produtos tanto em termos de aparência e sabor quanto em propriedades nutricionais. O objetivo deste trabalho foi quantificar os teores de compostos fenólicos totais, antocianinas, flavonóis e atividade antioxidante em maçãs da cultivar Gala e de duas mutações somáticas, Royal Gala e Galaxy Gala, com diferentes intensidades de pigmentação vermelha. Os teores de fenóis totais foram semelhantes nas frutas inteiras. A atividade antioxidante apresentou diferença significativa na fruta inteira, sendo que a cultivar Gala foi a que obteve maior valor (17559 µm.g-1) e a cv. Galaxy Gala, com pouca pigmentação, o menor (6160 µg.g-1). A cultivar Royal Gala apresentou valores intermediários de atividade antioxidante de 12050 µm.g-1, para as frutas com muita pigmentação vermelha, e 13546 µm.g-1 para as com pouca pigmentação. O teor de antocianinas na fruta inteira variou de 5,79 a 13,73 mg.100 g-1 e o teor de flavonóis oscilou entre 23,37 e 382,83 mg.100 g-1 nas cvs. Royal Gala e Galaxy Gala, respectivamente. Analisado nas diferentes partes das maçãs, o epicarpo apresentou a maior concentração de fenóis com aproximadamente 57% do conteúdo total e 42% da atividade antioxidante. Os compostos fenólicos e a atividade antioxidante nos sucos oxidados foram significativamente reduzidos com o escurecimento enzimático, com perdas de 69% e 83%, respectivamente. As frutas de mesma cultivar com maior e menor intensidade de cor apresentaram teores de compostos fenólicos e capacidade antioxidante semelhantes, porém as cultivares variaram significativamente.

Avaliação da eficiência de extração de compostos nitrogenados da polpa de anchoíta (Engraulis anchoita)

Este trabalho teve como objetivo avaliar a eficiência da extração de compostos nitrogenados, como proteínas solúveis (PS), nitrogênio total (NT), nitrogênio não proteico (NNP) e nitrogênio proteico (NP) da polpa de anchoíta (Engraulis anchoita), bem como obter informações a respeito de sua composição proximal e do frescor em relação ao seu local de captura. A polpa de anchoíta foi submetida a tratamento de extração de nitrogenados utilizando como soluções NaHCO3 (0,1; 0,2; 0,3 e 0,5%), NaCl 0,3% e água destilada. O ciclo de lavagem da polpa utilizando 0,1% de NaHCO3, dois ciclos de água destilada e um ciclo de NaCl 0,3% demonstrou maior eficiência na extração dos compostos nitrogenados, assim como das proteínas sarcoplasmáticas. Na determinação da composição proximal, a anchoíta in natura apresentou valores de umidade de 77,2%, proteína 16,8%, lipídios 3,4% e cinzas 2,4% e, para a polpa de anchoíta, foram encontrados valores de umidade de 78,1%, proteína 17,5%, lipídios 2,4% e cinzas 2,0%. A avaliação do frescor foi determinada através do pH, bases voláteis totais (N-BVT) e trimetilamina (N-TMA), encontrando-se valores de 6,3; 11,5 mg.100 g-1 e 2,8 mg.100 g-1 para a anchoíta in natura e 6,7; 20,2 mg.100 g-1; 3,1 mg.100 g-1 para a polpa, respectivamente.

Influência dos compostos nitrogenados na concentração de proteína da cianobactéria Aphanothece microscopica Nägeli

O trabalho teve como objetivo avaliar a influência dos compostos nitrogenados na concentração de proteína da cianobactéria Aphanothece microscopica Nägeli quando cultivada em meio de cultivo padrão BG11 e no efluente do processamento de pescado. As condições experimentais foram inóculo de 200 mg.L-1, 30 °C, pH 7,6 e razão C/N 20. As amostras foram retiradas no início, meio e fim da fase logarítmica e da fase estacionária e analisadas quanto à concentração de nitrogênio total, nitrogênio não proteico, amônio, nitrato, nitrito e ácidos nucleicos. Ficou demonstrado em todas as culturas que o íon amônio, juntamente com os ácidos nucleicos, representa uma importante fração do nitrogênio não proteico presente na biomassa. Os resultados mostraram que o meio de cultivo influencia a concentração de nitrogênio e que a determinação de proteína pelo método de Kjeldahl superestima a concentração proteica em cianobactérias.

A method to determine volatile contaminants in polyethylene terephthalate (PET) packages by HDC-GC-FID and its application to post-consumer materials

A simple and low cost method to determine volatile contaminants in post-consumer recycled PET flakes was developed and validated by Headspace Dynamic Concentration and Gas Chromatography-Flame Ionization Detection (HDC-GC-FID). The analytical parameters evaluated by using surrogates include: correlation coefficient, detection limit, quantification limit, accuracy, intra-assay precision, and inter-assay precision. In order to compare the efficiency of the proposed method to recognized automated techniques, post-consumer PET packaging samples collected in Brazil were used. GC-MS was used to confirm the identity of the substances identified in the PET packaging. Some of the identified contaminants were estimated in the post-consumer material at concentrations higher than 220 ng.g-1. The findings in this work corroborate data available in the scientific literature pointing out the suitability of the proposed analytical method.

Influência da fermentação e secagem de amêndoas de cacau no teor de compostos fenólicos e na aceitação sensorial

Devido à importância das etapas de fermentação e secagem das sementes de cacau para as características sensoriais dos produtos finais obtidos, bem como para os teores de compostos fenólicos presentes, objetivou-se avaliar a influência do tempo de fermentação e do tipo de secagem de sementes de cacaueiro nos teores de compostos fenólicos, bem como nas características físicas, físico-químicas e sensoriais dos produtos obtidos. Os tempos de fermentação avaliados foram 3 e 7 dias e a secagem foi realizada naturalmente (ao sol) e artificialmente (estufa com circulação de ar a 35 °C). Os teores de compostos fenólicos totais, flavan-3-óis e procianidinas foram quantificados durante a fermentação e ao término da secagem. Constatou-se que grande parte dos compostos fenólicos foi perdida durante a fermentação, sendo que as amêndoas fermentadas por 3 dias apresentaram teores maiores dos compostos fenólicos avaliados. Contudo, observou-se nessa condição uma significativa perda na qualidade sensorial. A secagem natural das amêndoas fermentadas permitiu maior retenção de polifenóis e também melhores resultados sensoriais em relação à secagem artificial. A avaliação sensorial realizada com uma bebida formulada com o liquor obtido dos diferentes tratamentos demonstrou que a amostra fermentada durante 7 dias apresentou as melhores notas sensoriais, sendo que o produto seco naturalmente foi o mais bem avaliado em relação aos demais.

Effect of adding unconventional raw materials on the technological properties of rice fresh pasta

The aim of this study was to develop fettuccini type rice fresh pasta by cold extrusion. To produce the pasta, a 2² Central Composite Rotational Design was used, in which the effects of the addition of pre-gelatinized rice flour - PGRF (0-60%) and modified egg albumin - MEA (0-10%) were studied. The dependent variables were the results of the cooking test and of the instrumental texture. The optimum cooking time for all of the formulations of rice fresh pasta was 3 minutes. MEA had a greater effect on increasing the weight of the pasta when compared to that of PGRF. It was found that with the addition of PGRF increase in loss of solids in cooking water, whereas MEA exerted the opposite effect on this parameter. Moreover, the maximum value of MEA (10%) had an optimum effect on pasta firmness, while PGRF had a negative effect on this parameter. The maximum values of PGRF and MEA reduced the stickiness of the pasta. Based on these results and on the parameters considered as most important, the rice pasta with the best technological characteristics was that with the maximum levels of MEA (10%) and no addition of PGRF (0%). This product was submitted to sensory and microbiological analyses, with good results.

Characterization of new sources of derivative starches as wall materials of essential oil by spray drying

Starch derivatives of taro (Colocasia esculenta L. Schott) and rice were characterized as wall materials of orange oil (d-limonene) by spray drying. Native starches were initially hydrolyzed with HCl and then esterified. Succinylated starches were modified using a conventional method in a slurry and were extruded; whereas, the phosphorylated starches were modified using the extrusion process. Viscosity and solubility of starches reduced after acid hydrolysis, derivatization, and extrusion. The particle size of the wall materials ranged between 20.05 and 31.81 µm. The encapsulation efficiency of the phosphorylated taro, rice, and waxy corn starches was 96.9, 96.8 and 97.1% respectively, and 98.6, 98.1, and 98.8% for succynilated taro, rice, and waxy corn starches, respectively. Starch derivatives of taro and rice could potentially be used as wall materials of orange oil d-limonene.

Effect of different covering materials used during the pre-harvest stage on the quality and storage life of 'Sultana Seedless' grapes

Covering the grapevine rows to delay the maturity and harvest date became widely practiced in 'Sultana Seedless' vineyards. The research work was conducted to test different cover materials (polypropylene cross-stitch, life pack, mogul and transparent polyethylene) in respect to their effects on grape quality and storability. Harvest was delayed for one month in covered plots. Harvested grapes were packed and transferred to storage rooms after pre-cooling. During packing, the grape clusters were sealed in PE bags with sulphur dioxide pads. The grapes were stored for 90 days in the first year and 120 days in the second year, at -0.5ºC and 90% RH. All the grape clusters were healthy and of marketable quality after 90 days of storage period. In the first year, at the end of the storage, only those grapes harvested from the rows covered with polypropylene cross-stitch showed fungal growth. The sensory quality scores revealed a lower level of preference after 120 days of storage. The effects of the covering materials tested were similar regarding grape quality and storage performance except the transparent polyethylene that damaged the grapevine leaves.

Compostos fenólicos inibidores da germinação em sementes de mamão (Carica papaya)

Sementes de mamão germinam lenta e irregularmente, o que tem sido atribuído à presença da sarcotesta. O trabalho teve como objetivos avaliar o efeito inibitório de extratos de sarcotesta na germinação de sementes de alface e quantificar compostos fenólicos em sementes de mamão. Foram utilizados frutos de mamão do grupo Formosa, híbrido Tainung 01, colhidos em Maio e Setembro/2005, obtendo-se sementes com e sem sarcotesta que foram avaliadas quanto à germinação aos 15 e 30 dias após a semeadura. Realizou-se um bioensaio com sementes de alface, que foram colocadas para germinar em substrato umedecido com água e com soluções obtidas a partir de extrato da sarcotesta de sementes de mamão. Determinou-se, também, o conteúdo de compostos fenólicos nas diferentes estruturas destas (sarcotesta, esclerotesta, endosperma e embrião), utilizando-se o ácido tânico como padrão e para reação de coloração, o reagente Folin-Ciacalteau, com leitura em espectrofotômetro a 765 nm. Verificou-se que o extrato de sarcotesta inibe a germinação e o crescimento da raiz primária das plântulas de alface, devido à presença de compostos fenólicos. Maior quantidade destes compostos foi observada na esclerotesta das sementes de mamão, seguida da sarcotesta, sendo praticamente nula a presença de tais compostos no embrião e no endosperma. Sementes oriundas da colheita de Maio/2005 exibiram dormência, apresentando maior conteúdo de fenóis na sarcotesta quando comparadas às sementes obtidas de frutos colhidos em Setembro/2005, as quais não apresentaram dormência.

Study on the properties of piezoelectric materials and manganese-based oxide perovskites /

Perovskite type piezoelectric and manganese oxide materials have gained a lot of attention in the field of device engineering. Lead zirconium titananium oxide (PbZri.iTiiOa or PZT) is a piezoelectric material widely used as sensors and actuators. Miniaturization of PZTbased devices will not only perfect many existing products, but also opens doors to new applications. Lanthanum manganese oxides Lai-iAiMnOa (A-divalent alkaline earth such as Sr, Ca or Ba) have been intensively studied for their colossal magnetoresistance (CMR) properties that make them applicable in memory cells, magnetic and pressure sensors. In this study, we fabricate PZT and LSMO(LCMO) heterostructures on SrTiOa substrates and investigate their temperature dependency of resistivity and magnetization as a function of the thickness of LSMO(LCMO) layer. The microstructure of the samples is analysed through TEM. In another set of samples, we study the effect of application of an electric field across the PZT layer that acts as an external pressure on the manganite layer. This verifies the correlation of lattice distortion with transport and magnetic properties of the CMR materials.

The design, synthesis and characterization of new building blocks for the preparation of molecule-based magnetic materials /

Two new families of building blocks have been prepared and fully characterized and their coordination chemistry exploited for the preparation of molecule-based magnetic materials. The first class of compounds were prepared by exploiting the chemistry of 3,3'-diamino-2,2'-bipyridine together with 2-pyridine carbonyl chloride or 2-pyridine aldehyde. Two new ligands, 2,2'-bipyridine-3,3'-[2-pyridinecarboxamide] (Li, 2.3) and N'-6/s(2-pyridylmethyl) [2,2'bipyridine]-3,3'-diimine (L2, 2.7), were prepared and characterized. For ligand L4, two copper(II) coordination compounds were isolated with stoichiometrics [Cu2(Li)(hfac)2] (2.4) and [Cu(Li)Cl2] (2.5). The molecular structures of both complexes were determined by X-ray crystallography. In both complexes the ligand is in the dianionic form and coordinates the divalent Cu(II) ions via one amido and two pyridine nitrogen donor atoms. In (2.4), the coordination geometry around both Cu11 ions is best described as distorted trigonal bipyramidal where the remaining two coordination sites are satisfied by hfac counterions. In (2.5), both Cu(II) ions adopt a (4+1) distorted square pyramidal geometry. One copper forms a longer apical bond to an adjacent carbonyl oxygen atom, whereas the second copper is chelated to a neighboring Cu-Cl chloride ion to afford chloride bridged linear [Cu2(Li)Cl2]2 tetramers that run along the c-axis of the unit cell. The magnetic susceptibility data for (2.4) reveal the occurrence of weak antiferromagnetic interactions between the copper(II) ions. In contrast, variable temperature magnetic susceptibility measurements for (2.5) reveal more complex magnetic properties with the presence of ferromagnetic exchange between the central dimeric pair of copper atoms and weak antiferromagnetic exchange between the outer pairs of copper atoms. The Schiff-base bis-imine ligand (L2, 2.7) was found to be highly reactive; single crystals grown from dry methanol afforded compound (2.14) for which two methanol molecules had added across the imine double bond. The susceptibility of this ligand to nucleophilic attack at its imine functionality assisted via chelation to Lewis acidic metal ions adds an interesting dimension to its coordination chemistry. In this respect, a Co(II) quaterpyridine-type complex was prepared via a one-pot transformation of ligand L2 in the presence of a Lewis acidic metal salt. The rearranged complex was characterized by X-ray crystallography and a reaction mechanism for its formation has been proposed. Three additional rearranged complexes (2.13), (2.17) and (2.19) were also isolated when ligand (L2, 2.7) was reacted with transition metal ions. The molecular structures of all three complexes have been determined by X-ray crystallography. The second class of compounds that are reported in this thesis, are the two diacetyl pyridine derivatives, 4-pyridyl-2,6-diacetylpyridine (5.5) and 2,2'-6,6'-tetraacetyl-4,4'-bipyridine (5.15). Both of these compounds have been designed as intermediates for the metal templated assembly of a Schiff-base N3O2 macrocycle. From compound (5.15), a covalently tethered dimeric Mn(II) macrocyclic compound of general formula {[Mn^C^XJCl-FkO^Cl-lO.SFbO (5.16) was prepared and characterized. The X-ray analysis of (5.16) reveals that the two manganese ions assume a pentagonal-bipyramidal geometry with the macrocycle occupying the pentagonal plane and the axial positions being filled by a halide ion and a H2O molecule. Magnetic susceptibility data reveal the occurrence of antiferromagnetic interactions between covalently tethered Mn(II)-Mn(II) dimeric units. Following this methodology a Co(II) analogue (5.17) has also been prepared which is isostructural with (5.16).

Low frequency Raman scattering in amorphous materials: fused quartz, "pyrex" boro-silicate glass and soda-lime silicate glass

Raman scattering in the region 20 to 100 cm -1 for fused quartz, "pyrex" boro-silicate glass, and soft soda-lime silicate glass was investigated. The Raman spectra for the fused quartz and the pyrex glass were obtained at room temperature using the 488 nm exciting line of a Coherent Radiation argon-ion laser at powers up to 550 mW. For the soft soda-lime glass the 514.5 nm exciting line at powers up to 660 mW was used because of a weak fluorescence which masked the Stokes Raman spectrum. In addition it is demonstrated that the low-frequency Raman coupling constant can be described by a model proposed by Martin and Brenig (MB). By fitting the predicted spectra based on the model with a Gaussian, Poisson, and Lorentzian forms of the correlation function, the structural correlation radius (SCR) was determined for each glass. It was found that to achieve the best possible fit· from each of the three correlation functions a value of the SCR between 0.80 and 0.90 nm was required for both quartz and pyrex glass but for the soft soda-lime silicate glass the required value of the SCR. was between 0.50 and 0.60 nm .. Our results support the claim of Malinovsky and Sokolov (1986) that the MB model based on a Poisson correlation function provides a universal fit to the experimental VH (vertical and horizontal polarizations) spectrum for any glass regardless of its chemical composition. The only deficiency of the MB model is its failure to fit the experimental depolarization spectra.

Phonon dispersion curves and atomic mean square displacement for several fcc and bcc materials

The atomic mean square displacement (MSD) and the phonon dispersion curves (PDC's) of a number of face-centred cubic (fcc) and body-centred cubic (bcc) materials have been calclllated from the quasiharmonic (QH) theory, the lowest order (A2 ) perturbation theory (PT) and a recently proposed Green's function (GF) method by Shukla and Hiibschle. The latter method includes certain anharmonic effects to all orders of anharmonicity. In order to determine the effect of the range of the interatomic interaction upon the anharmonic contributions to the MSD we have carried out our calculations for a Lennard-Jones (L-J) solid in the nearest-neighbour (NN) and next-nearest neighbour (NNN) approximations. These results can be presented in dimensionless units but if the NN and NNN results are to be compared with each other they must be converted to that of a real solid. When this is done for Xe, the QH MSD for the NN and NNN approximations are found to differ from each other by about 2%. For the A2 and GF results this difference amounts to 8% and 7% respectively. For the NN case we have also compared our PT results, which have been calculated exactly, with PT results calculated using a frequency-shift approximation. We conclude that this frequency-shift approximation is a poor approximation. We have calculated the MSD of five alkali metals, five bcc transition metals and seven fcc transition metals. The model potentials we have used include the Morse, modified Morse, and Rydberg potentials. In general the results obtained from the Green's function method are in the best agreement with experiment. However, this improvement is mostly qualitative and the values of MSD calculated from the Green's function method are not in much better agreement with the experimental data than those calculated from the QH theory. We have calculated the phonon dispersion curves (PDC's) of Na and Cu, using the 4 parameter modified Morse potential. In the case of Na, our results for the PDC's are in poor agreement with experiment. In the case of eu, the agreement between the tlleory and experiment is much better and in addition the results for the PDC's calclliated from the GF method are in better agreement with experiment that those obtained from the QH theory.