Centro de Ciências Exatas e Tecnológicas
URI permanente desta comunidadehttps://locus.ufv.br/handle/123456789/9791
Navegar
1244 resultados
Filtros
Configurações
Resultados da Pesquisa
Item Hunter color dimensions, sugar content and volatile compounds in pasteurized yellow passion fruit juice (Passiflora edulis var. flavicarpa) during storage(Brazilian Archives of Biology and Technology, 2004-06) Sandi, Delcio; Chaves, José Benício Paes; Sousa, Antônio Carlos Gomes de; Parreiras, June Ferreira Maia; Silva, Marco Túlio Coelho da; Constant, Patrícia Beltrão LessaChanges in Hunter L, a and b values, glucose, fructose and sucrose contents, concentration of four volatile compounds (ethyl butirate, ethyl caproate, hexyl butirate and hexyl caproate) and furfural, were studied in yellow passion fruit juice (Passiflora edulis var. flavicarpa) pasteurized at 75ºC/60s, 80ºC/41s or 85ºC/27s, during storage at room temperature (25±5ºC) and refrigeration (5±1ºC) for 120 days. While the sucrose content decreased, the glucose and fructose contents increased significantly over storage time. The Hunter L and b values behaved similarly, with a tendency to decrease over time, inversely to Hunter a value. Volatile compound concentrations also decreased over time, inversely to the furfural content. Pasteurization at 85ºC/27s resulted minimum changes in the studied passion fruit characteristics, while that at 75ºC/60s was the most harmful. Storage under refrigeration tended to keep the best quality characteristics of the juice.Item Microbiological air quality of processing areas in a dairy plant as evaluated by the sedimentation technique and a one-stage air sampler(Brazilian Journal of Microbiology, 2003-07) Salustiano, Valéria Costa; Andrade, Nélio José; Brandão, Sebastião César Cardoso; Azeredo, Raquel Monteiro Cordeiro; Lima, Sandra Aparecida KitakawaThe microbiological air quality at processing areas in a dairy plant was evaluated by using a one-stage air sampler, based on Andersen principles (impaction technique) and by culture settling plate technique, also known as sedimentation technique. Among these areas, milk reception, packaging, and pasteurization rooms were included. Rooms where cheese, yogurt, butter and "doce de leite"(Latin American typical treat made of concentrated milk and sugar) are made were also evaluated. For all processing areas, the numbers of mesophilic aerobic bacteria and yeast and molds recovered by air sampler were higher than 90 CFU·m-3 – the maximum value recommended by American Public Health Association (APHA). In four of the six processing areas, the microbial numbers were higher than APHA's standard (30 CFU.cm-2.week-1) according to culture settling plate technique. The results showed a difference (p<0.05) for the Staphylococcus aureus numbers (from <1.0 to 4.3 UFC·m-3) at processing areas. The numbers of microorganisms recovered by impaction technique were about 2 to 10 times higher than by sedimentation technique. The microorganism group determined at processing areas depended mainly on the technique. By the air sampler technique, it was observed the predominance of yeasts and molds and by sedimentation technique, of mesophilic aerobic bacteria. The increase of temperature at processing areas did not seem to affect the numbers of airborne microorganisms. On the other hand, the increase of air humidity showed a relation with the increase of microorganism numbers. The impaction technique should be chosen since it is better to recover airborne microorganisms, including pathogens.Item DLLME-GC/ECD Method for the Residual Analysis of Parathion-Methyl and its Application in the Study of the UV-Photodegradation Process(Journal of the Brazilian Chemical Society, 2017-11) Pimenta, Gustavo G.; Queiroz, Maria E. L. R. de; Victor, Raquel P. D.; Noronha, Luiz M.; Neves, Antônio A.; Oliveira, André F. de; Heleno, Fernanda F.A new method has been developed to determine trace levels of organophosphorus pesticide parathion-methyl in water samples by using dispersive liquid-liquid microextraction (DLLME), followed by gas chromatograph coupled with electron capture detector (GC/ECD) analysis. The optimized and validated method showed high extraction recovery (101.1%), high enrichment factor (57.3), low limits of detection and quantification, 0.083 and 0.250 µg L-1, respectively. The established DLLME-GC/ECD method has been successfully applied for the evaluation of the photodegradation of the parathion-methyl by UV254nm radiation in different conditions of pH and temperature. The parathion-methyl photodegradation at pH 3 and 35 °C achieved > 99.5% after 120 min of exposition. For this condition, it was observed the kinetic rate of 0.0515 min-1, the quantum yield of 1.22 × 10-5 mol Einstein-1 and a half-life time of 13.46 min. All experimental conditions tested proved to be strongly influenced by pH and temperature. The application of the optimized process in distilled and drinking water spiked with parathion-methyl provided residues of this pesticide at levels below the maximum permitted by Brazilian legislation, which is 9.0 µg L-1.Item Multivariate calibration to determine phorbol esters in seeds of Jatropha curcas l. Using near infrared and ultraviolet spectroscopies(Journal of the Brazilian Chemical Society, 2017-08) Roque, Jussara V.; Dias, Luiz A. S.; Teófilo, Reinaldo F.The building of partial least squares (PLS) regression models using near infrared (NIR) and ultraviolet (UV) spectroscopies to estimate the concentrations of phorbol esters (PEs) in Jatropha curcas L. is presented. The models were built using two algorithms for variable selection, ordered predictors selection (OPS) and genetic algorithm (GA). Chromatographic analyses were performed to determine the concentrations of PEs. Spectral data were obtained from seeds and oil extract. The results of PLS models were performed by analyzing statistical parameters of quality such as root mean square error of prediction (RMSEP) and correlation coefficient of external predictions (Rp). The parameters obtained for NIR-PLS and UV-PLS models with OPS were respectively: RMSEP 0.48 and 0.22 mg g-1 and Rp 0.49 and 0.96. For GA were obtained, respectively: RMSEP 0.52 and 0.28 mg g-1 and Rp 0.12 and 0.95. The models built from seeds and oil extracts can be used respectively for screening and to accurately predict the PEs content. The OPS method provided simpler and more predictive models compared to those obtained by the selection of variables using the GA. Thus, the UV-PLS-OPS model can be used as an alternative method to quantification of PEs.Item Desenvolvimento de um inquérito para avaliação da ingestão alimentar de grupos populacionais(Revista de Nutrição, 2006-09) Sales, Regiane Lopes de; Silva, Margarida Maria Santana; Costa, Neuza Maria Brunoro; Euclydes, Marilene Pinheiro; Tinôco, Adelson Luiz Araújo; Eckhardt, Vivian Fernandes; Rodrigues, Cláudia Márcia AntunesEste trabalho procurou desenvolver um instrumento para obtenção de dados relativos ao consumo alimentar, de caráter qualitativo e quantitativo, para avaliar a ingestão dietética em estudos populacionais. Inicialmente foram coletados dados sobre a ingestão alimentar de uma amostra representativa de moradores da cidade de Viçosa (n=119). Para conhecer os alimentos mais consumidos e seus porcionamentos, foram utilizados os métodos recordatório de 24h e pesagem direta. A entrevista ocorreu no horário do almoço ou jantar, com pesagem de todos os alimentos constantes na refeição e de porções referidas como consumidas nas últimas 24h, usou-se também álbum fotográfico como auxiliar na estimativa do peso da porção. A partir dos 60 alimentos mais consumidos e dos porcionamentos identificados, foi desenvolvido um inquérito baseado no método Freqüência de Consumo Alimentar semi-quantitativo, com 65 itens e um álbum fotográfico de alimentos. Realizou-se um estudo piloto para avaliação desta metodologia em uma sub-amostra (n=34). Para comparação entre os dois métodos, avaliaram-se o valor energético e os macronutrientes, utilizando o coeficiente de Pearson e o teste "t" de Student, tendo-se obtido: r=0,53 para energia, r=0,43 para proteína,r=0,58 para lipídeos e r=0,21 para carboidratos. Não foi detectada diferença significante entre os dois métodos para proteína e lipídeos, pelo teste "t" (a=0,05). O inquérito desenvolvido mostrou-se um instrumento promissor para inquéritos populacionais, no entanto, são necessários maiores estudos para averiguar as limitações e os possíveis desdobramentos do inquérito para atingir toda a populaçãoItem Removal of beta-lactams antibiotics through zero-valent copper nanoparticles(Journal of the Brazilian Chemical Society, 2018) Oliveira, Lucas M. F.; Nascimento, Mayra A.; Guimarães, Yuri M.; Oliveira, André F.; Silva, Antônio A.; Lopes, Renata P.The removal of the beta-lactam antibiotics (ceftriaxone and cefadroxil) through zero-valent copper nanoparticle (nZVC) was studied in this work. Excellent removal degrees (> 85%) were obtained for both analytes in only 20 min of reaction. Studies were performed in both oxic and anoxic conditions, and in the presence of t-butyl alcohol (TBA), an inhibitor of radicals. The results did not show significant changes. Therefore, the hydroxyl radicals are not the main species responsible for the removal. Total organic carbon cefadroxil analysis indicated a removal of 57% after 180 min of reaction. Studies involving Cu+ indicated that probably these are the principal species responsible for the removal of antibiotics. Kinetic studies have shown that two-phase reaction occurred in the antibiotics removal process and both phases followed pseudo-first order kinetic model. The first mechanism is related to the antibiotics degradation by Cu+ species and the second mechanism is related to the antibiotics adsorption by hydroxides/oxides of Cu2+ species.Item Applicability of a voltammetric assay based on the electroreduction of oxygen to evaluate the antioxidant capacity of Pequi (Caryocar brasiliense Camb.) Pulp(Journal of the Brazilian Chemical Society, 2018) Pinheiro, Flávia A.; Okumura, Leonardo L.; Silva, Astréa F. S.; Silva, Júnio G.; Ferreira, Letícia R.; Barcellos, Edilton S.; Fontes, Edimar A. F.This study aimed to use a differential pulse voltammetric (DPV) assay, based on the electroreduction of oxygen, to evaluate the antioxidant capacity of pequi pulp. The results were expressed in coefficient of antioxidant capacity (K), at different pH values and in trolox equivalent antioxidant capacity (TEAC), and were compared to the 2,2’-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) spectrophotometric assays. The principal component analysis showed higher K for pequi pulp extract and pH tending to 7.15. The antioxidant capacity was related to the presence of gallic acid in its composition. Regarding the TEAC value, the best result was obtained by the DPV test (53.43 ± 5.14 µmol trolox g-1 pulp). The pequi pulp showed antioxidant capacity, compared to the standard antioxidant compounds evaluated. It was concluded that the voltammetric protocol was efficient to assess the total antioxidant capacity of pequi pulp and can be an alternative to conventional spectrophotometric assays, for the analysis of food matrices.Item Preparation, X-ray structural studies and plant growth regulatory activity of methyl 6a,7b-thiocarbonyldioxyvouacapan-17 b-oate(Journal of the Brazilian Chemical Society, 2004-03) Rubinger, Mayura M. M.; Borges, Eduardo E. L.; Castelo-Branco, Pedro de A.; Guilardi, Silvana; Souza, Elysângela M. R.; Gambardella, Maria T. do P.; Ferreira-Alves, Dalton L.; Piló-Veloso, DorilaThe 6a,7b-dihydroxyvouacapan-17b-oic acid (1) and methyl 6a,7b-dihydroxyvouacapan-17b-oate (2) are natural products isolated from the hexane extract of Pterodon polygalaeflorus Benth fruits. Here we describe the preparation and characterization by infrared and nuclear magnetic resonance spectroscopy, and by elemental analysis of the novel derivative methyl 6a,7b-thiocarbonyldioxyvouacapan-17b-oate (5), from the ester 2. The structure of compound 5 was determined by X-ray diffraction. At the concentration of 100 ppm, this compound inhibited the radicle growth of Sorgum bicolor L. (-28%) and showed no significant effect on Cucumis sativus L..Item Características físico-químicas de ácidos húmicos em diferentes etapas da vermicompostagem(Eclética Química, 2010) Reis, E. L.; Reis, C.; Brighenti, C. R. G.Amostras de materiais coletados em diferentes estádios de vermicompostagem foram submetidas a procedimentos de extração de ácidos húmicos. Técnicas de titulação potenciométrica, termogravimetria (DTG), difração de raios X e espectrofotometria no uv/visível e no infravermelho foram utilizadas no estudo desses materiais. Os dados de titulação foram submetidos ao ajuste por regressão não-linear, determinando-se, assim, cinco valores de pKa característicos de cinco classes de grupos tituláveis. Nas curvas DTG, foram observadas duas etapas, sendo a primeira característica da separação de estruturas alifáticas e, ou, alicíclicas e a segunda, a decomposição de estruturas aromáticas. A difratometria de raios X apresentou diferenças marcantes nos resultados, principalmente nos três primeiros picos onde parecem ocorrer reorganização estrutural e polimerização ao longo do processo de vermicompostagem. Os espectros do infravermelho não apresentaram diferenciação entre os espectros. Os valores da razão E4/E6 encontrados estão de acordo com os característicos dos ácidos húmicos, mas não fornecem informações que possam contribuir para a elucidação da estrutura e formação desses ácidos.Item Evaluation of aerobic and anaerobic biodegradability and toxicity assessment of real pharmaceutical wastewater from industrial production of antibiotics(Brazilian Journal of Chemical Engineering, 2016-07) Marcelino, R. B. P.; Andrade, L. N.; Starling, M. C. V. M.; Amorim, C. C.; Barbosa, M. L. T.; Lopes, R. P.; Reis, B. G.; Leão, M. M. D.This study evaluates aerobic and anaerobic biodegradability and toxicity of a real pharmaceutical wastewater, which focuses on antibiotics production. Zahn-Wellens and Organization for Economic Cooperation and Development (OECD) methodologies were applied in order to verify the wastewater's biodegradability and Microtox® analysis was performed for toxicity tests. Tests achieved more than 89% and 63% of Total Organic Carbon reduction, showing 80% and 50% of antibiotic removal, for aerobic and anaerobic processes, respectively. Moreover, acute ecotoxicological tests revealed that both techniques decreased the toxic character of real pharmaceutical wastewater. Desorption tests showed that the antibiotic was not degraded, but, in fact, adsorbed onto the sludge. Since biological treatment is the most widely used method for industrial wastewater treatment, this study indicates that this kind of treatment is probably unable to mineralize antibiotics present in pharmaceutical wastewaters, which may induce the development of resistant pathogens. Therefore, efforts must be taken to elucidate the main mechanisms of biological antibiotic removal from wastewaters since the presence of antibiotics in the environment is considered to be an emerging environmental issue.