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Desorption and adsorption isotherms and drying characteristics of red kidney beans were studied using static and dynamic methods, respectively. The desorption and adsorption isotherms were determined at 60, 50, 40, 30, 20, and 10°C with 32–91% relative humidity (RH). The constant RHs were generated using six saturated salt solutions at constant temperatures. The drying characteristics were determined using a thin-layer dryer with drying air at 50, 40, and 30°C with 35 and 50% RH. The dimensions of the kidney beans before and after drying were measured and shrinkage and sphericity of the beans were calculated. A new method to evaluate the best-fitted equation to characterize the thin-layer drying data was developed. The best-fitted equations to describe the desorption and adsorption isotherms were the modified Chung–Pfost and modified Guggenheim–Anderson–deBoer. The red kidney beans only experienced a falling rate drying period and had a largest shrinkage in the length direction during drying. The ...

The aim of this work was to determine specifications for spray-drying manufacturing of sustained-release drug-loaded microparticles with potential application in dentistry. Chitosan was used as the microencapsulation polymer and ketoprofen as the model drug. A 1:1 chitosan/ketoprofen suspension was spray-dried under different operating conditions. The size distribution, morphology, total drug load, and release profile of the powders were characterized. In vitro release studies were performed with the powder samples entrapped in cellulose dialysis tubes. The microparticles produced had a narrow size distribution (mean diameter ranging from 2.11 to 3.27 µm), good sphericity, and a smooth surface. In vitro release studies showed a linear drug dissolution behavior.

The influence of the coating suspensions and particle properties on the coating process in a conventional spouted bed is presented. Glass beads were coated at fixed operating conditions with different formulations of aqueous polymeric coating suspensions in a spouted bed of laboratory scale. The wettability of the solids by the liquid was quantified by the contact angle and surface tension of the coating suspensions. The coating efficiency and particle growth were correlated with the adhesion of the coating suspension to the solid particle, which is a function of the solids and liquid characteristics. The physical properties of the coated particles—particle mean diameter, sphericity, bulk, absolute and apparent densities, porosity and flow velocity—were determined and compared to the properties of uncoated particles.

The changes in density and porosity and the microstructural development of apple tissue throughout the equilibration in osmotic treatments were analyzed for different osmotic solution concentrations. The effect of vacuum impregnation of the sample with the osmotic solution, before the osmotic treatment was also studied. Two periods were differentiated in the process. For relatively short term treatments (24–48 h) cell walls shrunk or separated from plasmalemma because of the cell water loss while compositional pseudoequilibrium was achieved. Afterwards for long term treatments, a bulk flux of osmotic solution into the fruit tissue occurred in line with the relaxation of mechanical energy accumulated in the deformed cell wall matrix. So, the true equilibrium (chemical plus mechanical), achieved when no changes either in sample composition or weight occurred, implied cell wall sphericity and sample volume recovery. However, some degree of irreversibility was observed in cell wall recovery, especial...

The concept of a normalized single particle drying curve has been integrated into a generic, heterogeneous fluid bed model in order to describe batch fluid bed drying. Drying curves have been measured for both single particles and fluid beds. Two different coarse-grained materials, aluminum silicate and a technical product, have been used. In general, fluid bed drying curves appear to be predictible on the basis of single particle data and with the help of the model. Dificulties may arise mainly with particles of low sphericity and a large initial moisture content. Model parameters are in the range indicated by general fluidization literature. However, Sherwood numbers for particle-to-fluid mass transfer in the- fluid bed are significantly lower than the values for single particles. This can hardly be attributed to bubbling and bypassing, since these effects have been explicitly accounted for in the model.

The thin-layer drying of corn was analyzed in tern of Fick⢙s second law for diffusion. For spherical kernels (sphericity 0.98) Fick's law for diffusion out of a sphere was found appropriate model experimental drying curves. The diffusion coefficients deter mined by mans of this equation and corrected by the square of the s~hericity were taken as the intrinsic diffusivities of corn grain. Dent kernels were modeled by means of Fick's law assuming three different geometries: sphere, ellipsoid and parallelopiped. It was found that although the “Fickian” model describes reasonably well theexperimntal drying curves in the three cases, the diffusion coefficients obtained from the sphere differ mkedly from those corresponding to the parallelopipd and ellipsoid. For these last two geometries the diffusion coefficients practically agree with the intrinsic diffusivities obtained for spherical kernels