Based on an observed decrease of effective thermal conductivity of milk during coagulation, a heated thermistor sensor was developed for monitoring curd formation. The thermistor was heated with a constant direct current, and its voltage was measured during milk coagulation, indicating a drop after the enzymatic reaction. The sensor was studied in the laboratory for different milk acidities, rennet concentrations, added calcium chloride, and coagulation temperatures. It was also tested in a commercial cheese plant for more than a month. The cutting time established by the cheesemaker in 16 experiments was compared with a prediction equation, and the standard error of prediction was 1.9 min.
The disposal of industrial effluents into the environment is an issue that has attracted attention of researchers and engineers with particular reference for produced water originating from the petroleum industry. Separation process using ceramic membranes has been an alternative used to obey requirements of environmental agencies in Brazil related to disposal of oil and grease. Accordingly, we have studied numerically the fluid flow into a separation module with tubular membrane. The conservation equations for mass, linear momentum, and mass transport in conjunction with the renormalization group k-e turbulence model were resolved with aid of the ANSYS CFX 12 commercial package. Results of the streamlines, vector velocity, pressure, velocity, and concentration fields are presented and analyzed. It was concluded that the proposed mathematical model predicts the behavior of the flow within the separation module and that increasing the level of turbulence and putting an impermeable section into the inlet region of the membrane reduce the effect of the polarization layer.
O presente trabalho tem como objetivo determinar a composição físico-química e dos compostos bioativos da casca de jabuticaba fresca, realizar a sua cinética de secagem em três diferentes temperaturas de ar de secagem, ajustar modelos matemáticos empíricos e difusivo aos dados experimentais, produzir o pó e avaliar efeito da temperatura de secagem sobre a sua composição. Os frutos foram colhidos, lavados e higienizados com solução de hipoclorito de sódio, em seguida os frutos foram despolpados manualmente e as frações sólidas, polpa, cascas e sementes foram separadas. As cascas de jabuticaba foram secas em estufa com circulação de ar nas temperaturas de 45, 50 e 55 ºC e velocidade de 1.0 m/s. Foram construídas as curvas da cinética de secagem, representadas pela razão do teor de água em função do tempo de secagem em minutos, ajustando aos modelos matemáticos de Handerson e Pabis, Logarítmico, Midilli, Page e Newton aos dados experimentais. Os modelos foram selecionados tomando-se como parâmetro a magnitude do coeficiente de determinação (R2) e a função qui-quadrado (). Logo após a secagem as cascas foram trituradas para obtenção do pó, o qual foi caracterizado antes e após a secagem quanto as características físicas, químicas, compostos bioativos e atividade antioxidante. As cascas frescas de jabuticaba apresentaram altos teores de compostos fenólicos totais e taninos totais. O modelo de Midilli se destacou dos demais por apresentar o maior valor de R2 (>99%) e o menor valor da função qui-quadrado (<0.000327) para as três temperaturas estudadas, em especial para a de 45 ºC. A cinética de secagem das cascas de jabuticaba mostrou que a temperatura influenciou no processo, e que a constante “k” aumentou com a sua elevação, e o tempo do processo diminuiu em função do seu aumento. A temperatura de 45 °C garantiu uma maior preservação dos compostos fenólicos totais, antocianinas totais e flavonoides totais do pó das cascas da jabuticaba, podendo ser uma alternativa como ingrediente na elaboração de vários produtos dentre eles: pão, bolo, biscoito, iogurte e bebida láctea por ter uma quantidade significativa desses compostos bioativos.
A Jabuticabeira (Myrciaria cauliflora) é uma árvore frutífera nativa brasileira, pertencente à família Myrtaceae, seus frutos possuem grande valor nutricional. As cascas de jabuticaba são uma fonte de antocianinas, os quais são poderosos compostos antioxidantes e apresentam atividade antimicrobiana. Contudo, as cascas de jabuticaba são geralmente descartadas, o que além de gerar resíduos poluentes, promove o desperdício de nutrientes e compostos potencialmente bioativos presentes nessa porção. Assim, com o objetivo de minimizar as alterações e perdas de determinados compostos bioativos, e consequentemente indicar o potencial do aproveitamento do resíduo em escala industrial, o presente trabalho tem com objetivo avaliar a cinética de secagem da casca de jabuticaba e ajustar modelos matemáticos aos dados experimentais. Os frutos foram adquiridos no comércio de Campina Grande/PB, selecionados de acordo com o grau de maturação apropriada para o processamento e ausência de danos físicos (injúrias), lavados e higienizados com solução de hipoclorito de sódio, em seguida foram despolpados manualmente para separação das frações sólidas, polpa, casca e sementes. A secagem foi realizada em uma estufa de circulação de ar forçado, na faixa de temperaturas 45, 50 e 55°C. Os dados experimentais da secagem foram ajustados aos modelos de Page, Midili e Henderson e Pabis. A cinética das cascas de Jabuticaba mostrou que a temperatura influenciou no processo de secagem, e constatou-se que a constante de secagem “k” aumentou com a sua elevação. Ademais, o modelo de Midili apresentou um melhor ajuste comparado aos demais métodos.
Fluids in terms of rheological behavior can be classified into Newtonians and non-Newtonians. Newtonians are fluids that have unique and absolute viscosities, because the ratio between shear stress and shear rate is constant. In the oil industry, most fluids, such as microemulsions, oil and polymeric solutions, do not exhibit Newtonian behavior. To understand the behavior of chemical fluids, it is necessary to analyze some parameters to interpret their properties and applicability. In this context, the present work aims to obtain and characterize microemulsion systems containing Alkali, Surfactant, and Polymer, and verify their applicability in advanced oil recovery. Thus, we obtained five microemulsion systems consisting of saponified coconut oil (surfactant), Butan-1-ol (co-surfactant), kerosene (oil phase), Na2CO3 (alkali), water and different percentages of the polymer. The systems were characterized by analyzes of particle diameter, surface tension, viscosity and rheological behavior using mathematical models. Droplet sizes showed characteristic values of micellar aggregates. Surface tension presented a slight elevation when the percentage of polymer in the microemulsion increased. Through the rheological study, it was possible to observe that experimental values were better adjusted to the Ostwald-de Waele “power-law” model. As the percentage of polymer in the system increased, we calculated the apparent viscosity of the systems and observed an increasing change in viscosity values, a result of great interest to enhanced oil recovery studies.
In recent years, attention has been given to the processes controlling the emission of oily effluents and their environmental impact. Many industrial processes generate large volumes of water contaminated with oil, called oily waters. The oily water must be treated before its discard in order to meet the criteria established by environmental agencies (for example in Brazil, 20 mg/L). In present days, the process of separating oil/water with ceramic membranes has attracted the attention of many researchers [1,2]. In this sense, the aim of this study is to evaluate the influence of the tangential inlet shape in the oil/water separation via ceramic membranes. We use a mathematical multiphase flow model to describe the oil-water separation, based on the particle model. Here oil is the dispersed phase while water the continuous phase. To model the turbulence effect we use the RNGk-εmodel. All simulations were carried out using the Ansys CFX ® commercial code. Results of streamlines and velocity, pressure and volume fraction of phase fields are present and analyzed. The numerical results indicate that no significant difference when using a circular or rectangular pipe with the same cross-sectional area.
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