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Search Results: 1 - 10 of 180659 matches for " Resende Jaime Vilela de "
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Medidas da condutividade térmica efetiva de modelos de polpas de frutas no estado congelado
Resende, Jaime Vilela de;Silveira Jr, Vivaldo;
Ciência e Tecnologia de Alimentos , 2002, DOI: 10.1590/S0101-20612002000200013
Abstract: the thermo physical properties of foods required in the simulation of freezing processes include density, conductivity and specific heat. in this work, thermal diffusivities and thermal conductivities of fruit pulp models were measured using the hot wire probe method. experiments were carried out from 0 to -25oc with food models constituted by 0,5% k-carrageenan + 10% sucrose (weight/volume in water). structural models were used for evaluating heat conduction combined with ice fraction predicted from the heldman models for the samples, and were compared with the measurement of effective thermal conductivity. the structural models used were: series, parallel and maxwell-eucken models with ice as the dispersed phase. with all the samples tested, the model, which was composed of the dispersed ice phase, showed the best results (underestimated on 6,13% when compared with experimental measurements) and was chosen for predicting the effective thermal conductivity of frozen fruit pulp model-solutions. the values calculated for the thermal conductivity were fitted in terms of polynomial functions of temperature, divided into four temperature ranges and could be used in the resolution of heat transfer problems in the freezing process.
Medidas da condutividade térmica efetiva de modelos de polpas de frutas no estado congelado
Resende Jaime Vilela de,Silveira Jr Vivaldo
Ciência e Tecnologia de Alimentos , 2002,
Abstract: As propriedades termofísicas de alimentos, necessárias nas simula es e cálculos do processo de congelamento, incluem principalmente a densidade, condutividade térmica e calor específico. Neste trabalho, as difusividades e condutividades térmicas da solu o, usadas como modelo para o congelamento de polpas de frutas, foram medidas pelo método da sonda com aquecimento. Os experimentos foram conduzidos na faixa de -25 a 0masculineC com modelos alimentícios constituídos de 0,5% de K- carrageenan + 10% de sacarose (massa/volume de água). Modelos estruturais foram usados para as avalia es da condu o de calor, combinada com a fra o de gelo predita para as amostras a partir dos modelos de Heldman e foram comparados com os valores das condutividades térmicas efetivas medidas. Os modelos estruturais empregados foram: em série, paralelo e Maxwell-Eucken, com o gelo considerado como a fase dispersa. Em todos os ensaios, o modelo de Maxwell-Eucken apresentou os melhores resultados (erro máximo de 6,13% quando comparado com os valores experimentais medidos) e foi escolhido para a predi o da condutividade térmica efetiva de solu es-modelo de polpas de frutas congeladas. Os valores calculados da condutividade térmica foram ajustados em termos de fun es polinomiais, divididas em quatro faixas de temperatura e podem ser usadas na resolu o dos problemas de transferência de calor, nos processos de congelamento.
Sele??o precoce intensiva: uma nova estratégia para o programa de melhoramento genético do cajueiro
Cavalcanti, José Jaime Vasconcelos;Resende, Marcos Deon Vilela de;
Revista Brasileira de Fruticultura , 2010, DOI: 10.1590/S0100-29452010000400043
Abstract: most breeding programs of perennial crops have great limitation on land availability for experimental plots. the purpose of this work is to introduce a new method here called "intensive early selection" (ies), to be used in the cashew breeding with the aim of increasing the genetic gain per area and time. it is a simple method that uses a density of plants four times higher than the traditional system and an early selection based on characters with high heritability, when the plants reach two years old. the analysis results demonstrate greater effectiveness and feasibility of applying this approach over the conventional system of breeding in this crop.
Escoamento de ar através de embalagens de polapa de frutas em caixas comerciais: efeito sobre os perfis de velocidade em túneis de congelamento
Resende, Jaime Vilela de;Neves Filho, Lincoln de Camargo;Silveira Jr., Vivaldo;
Ciência e Tecnologia de Alimentos , 2002, DOI: 10.1590/S0101-20612002000200014
Abstract: the changes in air velocity, as a function of stacking of fruit pulp packages (100g), offering a resistance to air flow in commercial boxes were evaluated and the air flow rates estimated during blast freezing operations. velocities were initially measured prior to passing the air through the multi-layer stacks of boxes in the chamber. processing of the data was accomplished by applying a non-linear regression routine. air flow rates were determined by numerical integration from adjusted air flow velocity profiles and appeared to be 10% higher than those obtained by the traditional procedure. under constant operating conditions of the fan, the results for the 7-layer arrays of boxed products exhibited a 62% reduction in the flux of chilling air, in relation to the 3-layer arrays, and 50.9% decrease with respect to the 5-layer array. these values were directly proportional to the void space available for air flow.
Air blast freezing of fruit pulp models in commercial boxes: influence of preferential channels in the bed on freezing times estimating
Resende, Jaime Vilela de;Silveira Jr., Vivaldo;Neves Filho, Lincoln de C.;
Ciência e Tecnologia de Alimentos , 2002, DOI: 10.1590/S0101-20612002000300021
Abstract: the freezing times of fruit pulp models packed and conditioned in multi-layered boxes were evaluated under conditions similar to those employed commercially. estimating the freezing time is a difficult practice due to the presence of significant voids in the boxes, whose influence may be analyzed by means of various methods. in this study, a procedure for estimating freezing time by using the models described in the literature was compared with experimental measurements by collecting time/temperature data. the following results show that the airflow through packages is a significant parameter for freezing time estimation. when the presence of preferential channels was considered, the predicted freezing time in the models could be 10% lower than the experimental values, depending on the method. the isotherms traced as a function of the location of the samples inside the boxes showed the displacement of the thermal center in relation to the geometric center of the product.
Air blast freezing of fruit pulp models in commercial boxes: influence of preferential channels in the bed on freezing times estimating
Resende Jaime Vilela de,Silveira Jr. Vivaldo,Neves Filho Lincoln de C.
Ciência e Tecnologia de Alimentos , 2002,
Abstract: The freezing times of fruit pulp models packed and conditioned in multi-layered boxes were evaluated under conditions similar to those employed commercially. Estimating the freezing time is a difficult practice due to the presence of significant voids in the boxes, whose influence may be analyzed by means of various methods. In this study, a procedure for estimating freezing time by using the models described in the literature was compared with experimental measurements by collecting time/temperature data. The following results show that the airflow through packages is a significant parameter for freezing time estimation. When the presence of preferential channels was considered, the predicted freezing time in the models could be 10% lower than the experimental values, depending on the method. The isotherms traced as a function of the location of the samples inside the boxes showed the displacement of the thermal center in relation to the geometric center of the product.
Escoamento de ar através de embalagens de polapa de frutas em caixas comerciais: efeito sobre os perfis de velocidade em túneis de congelamento
Resende Jaime Vilela de,Neves Filho Lincoln de Camargo,Silveira Jr. Vivaldo
Ciência e Tecnologia de Alimentos , 2002,
Abstract: As varia es nas velocidades do ar causadas pela resistência ao escoamento em fun o da quantidade de embalagens de polpa de frutas (100g), acondicionadas em caixas comerciais durante o processo de congelamento, foram avaliadas e as vaz es estimadas, com base em um método de tratamento dos dados experimentais. As velocidades foram medidas antes da passagem do ar pelo empilhamento de caixas na camara. As medi es foram analisadas utilizando-se uma rotina de regress o n o linear e as vaz es determinadas pelo método de integra o numérica dos perfis das velocidades ajustadas. O método apresentou estima o 10% superior à encontrada pelo método tradicional. Mantendo as condi es operacionais do ventilador constantes, a vaz o para arranjos de sete camadas resultou ser 62% inferior à de três camadas e, 50,9% inferior à de cinco camadas. Estes valores foram proporcionais à redu o do espa o livre para escoamento do ar.
Armazenamento de mel?o 'Orange Flesh' minimamente processado sob atmosfera modificada
Prado, M?nica Elisabeth Torres;Chitarra, Adimilson Bosco;Resende, Jaime Vilela de;
Ciência e Agrotecnologia , 2005, DOI: 10.1590/S1413-70542005000200011
Abstract: the increase of the demand for products minimally processed brings a great challenge for the food science and technology, considering the shortage of information about the maintenance of the quality of those products. the storage of those products in appropriate conditions is a fundamental point for the success of such technology. the objective of this work was to evaluate the effect of the active modified atmosphere on the quality and conservation of the 'orange flesh' melons processed minimally. the fruits, after the processing, were wrapped under modified atmosphere (passive ma - control, active ma- with 5% of co2 and 5% of o2 and active ma with 10% of co2 and 2% of o2), stored in a cold chamber (6 ± 1 oc and 85 ± 5% rh) during 8 days and sampled for analyses of ph, total soluble solids, tritable acidity, total soluble sugars, firmness, total pectin, soluble pectin and pectinametylesterase and polygalacturonase activities every 2 days of storage. the variables firmness, total acidity and total pectin were not affected by the active modified atmosphere. however, smaller solubilization of pectins were detected in melons under atmosphere with 10% of co2 and 2% of o2. enzymatic activity was not detected in fruits from all treatments.
Avalia??o do processo de impregna??o a vácuo em mel?o, utilizando diferentes substancias
Reno, Marciu José;Resende, Jaime Vilela de;Prado, M?nica Elisabeth Torres;
Ciência e Agrotecnologia , 2010, DOI: 10.1590/S1413-70542010000500027
Abstract: cylindrical cuts of melon (cucumis melo var inodorus naudin, yellow type) were submitted to impregnation with calcium chloride solutions (0.5 g.100 ml-1 of solution) added with gelatinized starch (0. 5 and 10 g.100 ml-1 of solution) and glucose (0. 10 and 20 g.100 ml-1 of solution) with controlled vacuum pressure (84.4; 50.5 and 16.6 kpa). measurements of the total soluble solids, incorporation or loss components (turgidity) and texture of melon slices were made before and after vacuum impregnation. quality parameter variations were calculated in relation to the original fruit. alterations in the viscosity of the solutions during the processing had been also quantified. the existence of synergistic processes between the solute flows from the fruit and from the solution was evident and could be analyzed using response surfaces for the different pressures as a function of the glucose and gelatinized starch concentrations in the solutions. the molecular mobility of components of the fruit and the solution related to viscosity was discussed.
Microstructural changes of frozen strawberries submitted to pre-treatments with additives and vacuum impregnation
Reno, Marciu José;Prado, M?nica Elisabeth Torres;Resende, Jaime Vilela de;
Ciência e Tecnologia de Alimentos , 2011, DOI: 10.1590/S0101-20612011000100038
Abstract: strawberries were submitted to freezing after pre-treatments with hydrocolloid and calcium salts (pectin and calcium chloride) at different concentrations, in the attempt to establish a correlation of the effects of these substances and their processing, on the physical and microstructural characteristics of fruits after thawing. strawberry halves were submitted to impregnation with controlled vacuum pressure of 84.4, 50.5 and 16.6 kpa; comprising pectin at concentrations of 0, 1.5 and 3%; with the addition of calcium chloride at concentrations of 0, 3 and 6%; and glucose at 20%, for 4 hours. measurements were made of the total soluble solid contents, cellular fluid loss, texture and viscosity of the solution, before and after the freezing/thawing. images of the tissue cuts during the freezing, in function of time, were taken in an optic microscope coupled to a cold-stage and controlled temperature system, where the reduction of the cellular area was quantified using an image analyzing software. the pectin concentration had an influence on and demonstrated a potential for protection of the frozen tissue samples. the photomicrographs showed that the loss of cellular fluid occurs during the growth of ice formed in the intercellular spaces and it is retarded through treatments with high pectin concentrations.
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