KINETICS OF THE LIQUID-PHASE HYDRATION OF ACETYLENE CATALIZED BY A PARTIALLY MERCURIZED, SULFONIC ION-EXCHANGE RESIN

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Evaluation of water and sucrose diffusion coefficients in potato tissue during osmotic concentration

The water and sucrose effective diffusion coefficients behavior were studied in potato tubers immersed in aqueous sucrose solution, 50% (w/,A), at 27 degreesC. Water and sucrose concentration profiles were measured as function of the position for 3, 6 and 12 h of immersion. These were adjusted to a mathematical model for three components that take into account the bulk flow in a shrinking tissue and the concentration dependence of the diffusion coefficients. The binary effective coefficients were an order of magnitude lower than those for pure solutions of sucrose. These coefficients show an unusual concentration dependence. Analysis of these coefficients as functions of the concentration and position demonstrates that, cellular tissue promotes high resistance to diffusion in the tuber and also the elastic contraction of material influences the species diffusion. (C) 2003 Elsevier Science Ltd. All rights reserved.57436737

Experimental study of fluidized bed agglomeration of acerola powder

The aim of this work was to study the main effects of acerola powder on fluidized bed agglomeration. A 2(4-1) fractional factoring design was used to evaluate the main operating conditions (fluidizing air temperature, fluidizing air velocity, atomizing air flow and height of nozzle in the bed). The mechanical and physicochemical product changes were determined by analysis of particle diameter, moisture content, wetting time and bed porosity. The particle enlargement by agglomeration occurred when the relative humidity in the bed increased and, thus, the moisture of the product increased. However, the excessive increase in relative humidity resulted in a decrease in yield, caused by caking and product incrustation. The consolidation of small granules resulted in an increase in the instant properties, decreasing the wetting time and increasing the solubility in a short period of agitation.251515

Image analysis: Statistical study of particle size distribution and shape characterization

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Image analysis can serve as a fast and convenient approach for the analysis of particle size and shape. However, there is no consensus as to the minimum number of particles required for such analysis and the statistical methodology to be used in its evaluation. Four methodologies for determination of this minimum number for particle size distribution analysis and two for that of particle shape were tested using particles of guava juice powder and guava juice powder granulated in a fluidized bed. The Chi-Square test proved to be a robust and efficient mean for determination of particle size distribution and particle shape characterization. 550 particles was found to be the minimum number of particles necessary for the determination of the particle size distributions, with 100 particles required for determination of the shape descriptors for this specific material. (c) 2011 Elsevier B.V. All rights reserved.21415763Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Experimental study and optimization of the agglomeration of acerola powder in a conical fluid bed

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)The aim of this work was to study the physical property modifications of acerola powder produced by a wet-agglomeration process in a fluid bed, A 2(2) full experimental design was used to evaluate The influence of the main operational conditions and to optimize the agglomeration process. The product transformations were determined by an analysis of the particle diameter, size distribution, morphology, moisture content and solubility. The agglomeration of small granules results in an increase in the instant properties, increasing particle solubility. (c) 2008 Elsevier B.V. All rights reserved.1883187194The National Counsel of Technological and Scientific DevelopmentConselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

EVALUATION OF DIFFUSION-COEFFICIENTS IN OSMOTIC CONCENTRATION OF BANANAS (MUSA-CAVENDISH LAMBERT)

The effect of time of exposure, solution concentration and temperature on the osmotic concentration of banana (slices of 11 mm thickness) was studied in aqueous sucrose solutions. The selectivity of the cellular tissues was reduced by steam blanching the banana slices before osmotic treatment. Effective diffusion coefficients for the loss of water and the increase in sucrose content were determined according to Fick's Law applied to a two-dimensional body; calculated on the basis of the concentration of various components in the liquid phase impenetrating the fruit. These coefficients revealed values similar to binary diffusion coefficients for pure sucrose solutions.30219921

Amaranthus cruentus flour edible films: Influence of stearic acid addition, plasticizer concentration, and emulsion stirring speed on water vapor permeability and mechanical properties

Films forming solutions composed of Amaranth (Amaranthus cruentus) flour (4.0 g/100 mL), stearic acid (5-15 g/100 g of flour), and glycerol (25-35 g/100 g of flour) were prepared by an emulsification process, with varying stirring speed values (6640-13360 rpm). The influence of these parameters ( stearic acid and glycerol concentrations and stirring speed) on the water vapor barrier and mechanical properties of films was evaluated using the response surface methodology (RSM). Other characterizations, including microstructure, water solubility, and oxygen permeability, were performed in optimized films. According to statistical analysis results, the optimized conditions corresponded to 10 g of stearic acid/100 g of flour, 26 g of glycerol/100 g of flour, and a stirring speed of 12 000 rpm. The films produced under these conditions exhibited superior mechanical properties (2.5 N puncture force, 2.6 MPa tensile strength, and 148% elongation at break) in comparison to those of other protein and polysaccharide composite films, low solubility (15.2%), and optimal barrier properties (WVP of 8.9 x 10(-11) g m(-1) s(-1) Pa-1 and oxygen permeability of 2.36 x 10(-13) cm(3) m(-1) s(-1) Pa-1).54186645665

Simulation and Optimization of Semicontinuous Industrial Tunnel Dryers for Fruits

Semicontinuous industrial tunnel dryers were simulated and optimized for concurrent and countercurrent configurations. Mass and energy balances for the solid and gas phase were used to describe the operation of the dryer and a semi-empirical model for the mass transfer rate; the drying rate equation parameters were fitted using experimental data for Italy grapes. The simulation programs coded in Fortran 90 calculate the moisture and temperature profiles for grapes and humidity and temperature for air throughout the tunnel, cycle time, recirculation ratio, thermal load, and fresh air flow rate. The optimization minimizes the energy input considering the degradation of ascorbic acid in the fruit as the main constraint.27342843

Isolation and characterization of cellulose nanofibers from banana peels

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Cellulose nanofibers were isolated from banana peel using a combination of chemical treatments, such as alkaline treatment, bleaching, and acid hydrolysis. The suspensions of chemically treated fibers were then passed through a high-pressure homogenizer 3, 5, and 7 times, to investigate the effect of the number of passages on the properties of the resulting cellulose nanofibers. The cellulose nanofibers isolated in this study had a dry basis yield of 5.1 %. Transmission electron microscopy showed that all treatments effectively isolated banana fibers in the nanometer scale. The micrographs of the process steps used to isolate the nanofibers revealed gradual removal of amorphous components. Increasing number of passages in the homogenizer shortened the cellulose nanofibers while furnishing more stable aqueous suspensions with zeta potential values ranging from -16.1 to -44.1 mV. All the samples presented aspect ratio in the range of long nanofibers, hence being potentially applicable as reinforcing agents in composites. X-ray diffraction studies revealed that homogenized nanofiber suspensions were more crystalline than non-homogenized suspensions. Fourier transform infrared spectroscopy confirmed that alkaline treatment and bleaching removed most of the hemicellulose and lignin components present in the banana fibers. Thermal analyses revealed that the developed nanofibers exhibit enhanced thermal properties. In general, the nanoparticles isolated from the banana peel have potential application as reinforcing elements in a variety of polymer composite systems.211417432Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Behavior of plant tissue in osmotic solutions

The effect of the concentration of sucrose solutions on the cellular structure of potato tissue in equilibrium at 27 degreesC was Studied. Two different methods of investigation were used to determine the volume of the different phases composing the cellular tissue of the potato when in equilibrium with the solutions. one based on data of the concentration itself and the overall volume of 2 mm slices after 48 h at equilibrium, and the other on microscopic images of cells in thin slices of fresh tissue stained with neutral red after an hour in equilibrium to show protoplasts, vacuoles and plasmolysis spaces. The results of these methods were compared with those obtained by a predictive thermodynamic approach considering the semipermeability of cell membranes. Phase volume data obtained from microscopic analysis were more similar to what was predicted by the theoretical model than those obtained by means of composition measurement. where the long equilibrium time apparently led to the loss of semi permeability of the cell membranes, since total volumes calculated without consideration of the cell membranes were similar to those measured. This suggests that the length of time of osmotic dehydration brings about a change in cell structure and the consequent involvement of a different mechanism in mass transfer. (C) 2002 Elsevier Science Ltd. All rights reserved.56111