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Vacuum Drying (vacuum + drying)
Selected AbstractsImproving Grape Quality Using Microwave Vacuum Drying Associated with Temperature ControlJOURNAL OF FOOD SCIENCE, Issue 1 2007C. D. Clary ABSTRACT:, Microwave (MW) vacuum dehydration using temperature to control the level of MW power demonstrated potential in improving the performance of the process. Product surface temperature measured by an infrared temperature sensor was used to control MW power at any level between 0 and 3 kW. Multiple linear regression analysis indicated an r2= 0.942 for prediction of final moisture content and r2= 0.985 for prediction of puffed character of grapes based on product temperature, time, specific energy, fresh fruit sugar, and fresh fruit moisture content. Temperature was found to be the most significant predictor. The elemental and compound contents of grapes dried using MW vacuum was compared to sun-dried raisins. The grapes dried using MW vacuum exhibited better preservation. Vitamin A was found in the MW-vacuum-dried grapes but none was detected in the raisins, and Vitamin C, thiamine, and riboflavin were also higher in the MW-vacuum-dried grapes than in the raisins. [source] A new technique for foaming submicron size poly(methyl methacrylate) particlesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2007Hiroyuki Ogawa Abstract About 0.7,2 ,m diameter poly (methyl methacrylate) (PMMA) foamed particles were prepared via thermally induced phase separation (TIPS) from a PMMA/ethanol mixture and vacuum dried. It was found that ethanol, known to be a poor solvent to PMMA, could dissolve PMMA when the temperature was over 60°C. The solubility of PMMA (Mw = 15,000 and Mw = 120,000) in ethanol was measured and was found to increase as the temperature increased. PMMA particles on the scale of submicron and single micron diameter could be precipitated from the PMMA/ethanol solution by temperature quenching. Then, since the precipitated particles contained a certain amount of ethanol, the precipitated particles could be foamed using the ethanol as a foaming agent in a vacuum drying process. Vacuum drying at temperatures slightly below the glass transition temperature of the polymer could make the particles foam. The effects of foaming temperature and the molecular weight of the polymer on the size of foamed particles were investigated. The experimental results showed that the vapor pressure and the molecular weight of the polymer are key factors determining the expandability of the micro particles. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 [source] Vacuum drying of wood with radiative heating: I. Experimental procedureAICHE JOURNAL, Issue 1 2004Patrick Perré Abstract Experimental results for the vacuum drying of wood with radiative heating are presented. In particular, the temperature and pressure measurements at different locations within the board are provided, as are the overall drying curves. The heat source is such that the temperature at the end of the process remains low (,150°C), and under these conditions, the drying process resembles convective drying with superheated steam. Further important details concerning the internal transfer mechanisms that are induced by this drying process can be pointed out by comparing results for sapwood and heartwood of different species (Picea abies, Abies alba and Fagus silvatica). These extensive experimental data sets will be used in Part II of this work for the purposes of assessing the accuracy and predictive ability of two different drying models and for analyzing the vacuum drying process further at a fundamental level. © 2004 American Institute of Chemical Engineers AIChE J, 50:97,107, 2004 [source] Vacuum drying of wood with radiative heating: II.AICHE JOURNAL, Issue 1 2004Comparison between theory, experiment Abstract In part I of this work extensive experimental data sets for the vacuum drying of wood with radiative heating were presented for sapwood and heartwood of different species (Picea abies, Abies alba, and Fagus silvatica). These data sets are used here to validate two previously developed drying models. The first drying model, which is known as TransPore, is a comprehensive model able to capture the intricately coupled heat- and mass-transfer mechanisms that evolve throughout the drying process. The second model, which is known as Front_2D, uses a number of simplifying assumptions to reduce the complexity of the comprehensive model to a system that enables a semianalytical approach to be exploited for its solution. Although the first model provides a more accurate description of the entire process, the second model is able to produce representative solutions very efficiently in terms of overall computational times, making it a viable option for on-line control purposes. The comparison with experimental data highlights that both models are able to capture all of the observed trends, allowing them to be used with confidence for investigating the vacuum drying process at a fundamental level. The new contribution of this work lies in the fact that both models are used here for the first time to simulate drying at a reduced external pressure. © 2004 American Institute of Chemical Engineers AIChE J, 50: 108,118, 2004 [source] Studies on different combined microwave drying of carrot piecesINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 10 2010Wei-Qiang Yan Summary Three different combined microwave (MW) drying methods were compared, namely microwave-assisted vacuum drying (MWVD), microwave-assisted freeze drying (MWFD), microwave-enhanced spouted bed drying (MWSD), in terms of drying rate, drying uniformity, product colour, rehydration ratio, retention of , - carotene and vitamin C, and energy consumption. The drying rate of MWVD and MWSD were much faster than that of MWFD. The largest drying rate was obtained in MWSD with 3.5 W g,1. In general, the colour of MWSD products was very uniform. Rehydration ratio of MWFD carrot pieces was almost the same as the freeze-dried (FD) products and better than MWVD and MWSD products. In addition, the highest retention of carotene and vitamin C was observed in MWFD carrot pieces. No significant differences were observed in carotene and vitamin C between MWVD and MWSD products. However, the energy consumption in MWFD was the highest. [source] Carbon dioxide extraction of residual chloroform from biodegradable polymersJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 5 2002Wendy S. Koegler Abstract Biodegradable polymeric devices for drug delivery and tissue engineering are often fabricated with the use of organic solvents and may still contain significant amounts of solvent (> 1 wt%) even after aggressive vacuum drying. This excess solvent can interfere with tissue response and the mechanical properties of the devices. The aim of this article is to demonstrate that liquid CO2 extraction can be used to reduce residual solvent in dense poly(L -lactide-co-glycolide) devices to 50 ppm relatively quickly and with minimal changes in architecture under some conditions. Two liquid CO2 extraction systems were developed to examine the removal of residual solvents from bar-shaped PLGA devices: (1) a low-pressure (1400 psi) batch system, and (2) a high-pressure (5000 psi) continuous-flow system. Eight hours of extraction in the high-pressure system reduced residual chloroform in 3 mm thick bars below the 50-ppm target. A simple Fickian diffusion model was fit to the extraction results. Diffusion coefficients ranged from 1.10×10,6 cm2/s to 2.64×10,6 cm2/s. The model predicts that ,1 h is needed to dry 1-mm bars to chloroform levels below 50 ppm, and 7 h are needed for 3 mm thick bars. The micro- and macroarchitectures of porous PLGA scaffolds created by particulate leaching were not significantly altered by CO2 drying if the salt used to make the pores was not removed before drying. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res (Appl Biomater) 63: 567,576, 2002 [source] Vacuum drying of wood with radiative heating: I. Experimental procedureAICHE JOURNAL, Issue 1 2004Patrick Perré Abstract Experimental results for the vacuum drying of wood with radiative heating are presented. In particular, the temperature and pressure measurements at different locations within the board are provided, as are the overall drying curves. The heat source is such that the temperature at the end of the process remains low (,150°C), and under these conditions, the drying process resembles convective drying with superheated steam. Further important details concerning the internal transfer mechanisms that are induced by this drying process can be pointed out by comparing results for sapwood and heartwood of different species (Picea abies, Abies alba and Fagus silvatica). These extensive experimental data sets will be used in Part II of this work for the purposes of assessing the accuracy and predictive ability of two different drying models and for analyzing the vacuum drying process further at a fundamental level. © 2004 American Institute of Chemical Engineers AIChE J, 50:97,107, 2004 [source] Vacuum drying of wood with radiative heating: II.AICHE JOURNAL, Issue 1 2004Comparison between theory, experiment Abstract In part I of this work extensive experimental data sets for the vacuum drying of wood with radiative heating were presented for sapwood and heartwood of different species (Picea abies, Abies alba, and Fagus silvatica). These data sets are used here to validate two previously developed drying models. The first drying model, which is known as TransPore, is a comprehensive model able to capture the intricately coupled heat- and mass-transfer mechanisms that evolve throughout the drying process. The second model, which is known as Front_2D, uses a number of simplifying assumptions to reduce the complexity of the comprehensive model to a system that enables a semianalytical approach to be exploited for its solution. Although the first model provides a more accurate description of the entire process, the second model is able to produce representative solutions very efficiently in terms of overall computational times, making it a viable option for on-line control purposes. The comparison with experimental data highlights that both models are able to capture all of the observed trends, allowing them to be used with confidence for investigating the vacuum drying process at a fundamental level. The new contribution of this work lies in the fact that both models are used here for the first time to simulate drying at a reduced external pressure. © 2004 American Institute of Chemical Engineers AIChE J, 50: 108,118, 2004 [source] Comparison of single pot and multiphase high shear wet granulation processes related to excipient compositionJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 10 2009K. Giry Abstract At present time, industrial production imperatives can require the transposition of a formulation from one equipment to another. In order to evaluate the impact of such a switch on the properties of granules and tablets, investigations were undertaken on formulations manufactured both in a single pot mixer-granulator-dryer (high shear granulator with in situ double jacket vacuum drying) and in a multiphase equipment (high shear granulator/fluid bed dryer). Principal component analysis highlighted the major contribution of the binder ratio on granule size distribution, flow and packing ability whereas the relative ratio of mannitol and lactose, used as fillers, mainly impacted on compressibility and tablet cohesion. In the studied domain, the lubricant ratio did not explain the considered responses. Statistical analysis (comparison of means, analysis of variance and PCA) showed that both processes led to products with similar characteristics which demonstrated the ability of the processes to produce granules with close quality. However, Fielder®/Niro® granule characteristic data were found to be more dispersed, thus demonstrating a higher sensitivity of the multiphase process to formulation changes. Technological properties of granules and tablets were found to be maintained or improved therefore securing the switch from single pot to multiphase equipments. © 2009 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 98:3761,3775, 2009 [source] Removal of N -methylpyrrolidone hydrogen-bonded to polyaniline free-standing films by protonation,deprotonation cycles or thermal heatingPOLYMER INTERNATIONAL, Issue 11 2001Eduardo A Ponzio Abstract Free-standing films of polyaniline (PANI), in an emeraldine base state, prepared by evaporation of polymer solutions in N -methylpyrrolidone (NMP) retain solvent even under dynamic vacuum drying as indicated by transmission Fourier transform infrared (FTIR) spectroscopy, where a band at 1670,cm,1 is clearly observed. Upon protonation,deprotonation cycles in aqueous media the weight of the dry base film decreases indicating gradual loss of NMP. Transmission FTIR spectra shows also the washing out of NMP with a clear decrease in intensity of the hydrogen-bonded >CO stretching band (1670,cm,1) of NMP. During this process the bands between 3500 and 3200,cm,1, assigned to >NH stretching in the PANI backbone, change intensity suggesting that intermolecular hydrogen-bonded >NH, with carbonyl oxygen of NMP, is replaced by free >NH. This is clear evidence of specific interaction of NMP with the emeraldine base. A similar loss of NMP is observed during heating but evidence of polymer degradation is also present. A mechanism is proposed to account for the loss of hydrogen-bonding ability upon protonation which requires delocalization of the radical cations in the protonated films. © 2001 Society of Chemical Industry [source] Alternative Drying Processes for the Industrial Preservation of Lactic Acid Starter CulturesBIOTECHNOLOGY PROGRESS, Issue 2 2007Chalat Santivarangkna The preservation of lactic acid starter cultures by alternative drying processes has attracted increasing attention due to the high costs and energy consumption of freezing and freeze drying. This review thus aims to provide a survey regarding the state of knowledge of starter culture production at high levels of viability. The results from numerous studies on various drying processes and lactic acid bacteria are summarized. The alternative drying processes considered, such as spray drying, fluidized bed drying, and vacuum drying, are mainly of industrial interest. The features, advantages, and disadvantages of these drying processes are described. In conclusion, the important factors that need to be considered, standardized, or optimized to achieve high levels of viability include intrinsic tolerance of cultures, growth media and conditions, stress induction, cell harvesting conditions, protective agents, rehydration conditions, enumeration of cells, and storage conditions. [source] Anwendungen der Magnetresonanz zur Untersuchung von Wasser-, Temperatur- und Porenverteilung bei lebensmittelverfahrenstechnischen ProzessenCHEMIE-INGENIEUR-TECHNIK (CIT), Issue 4 2004M. Regier Dr.-Ing. Abstract Es werden verschiedene Methoden der kernmagnetischen Resonanz (NMR) und ihrer Anwendung zur Bestimmung von Wasser-, Temperaturverteilungen und Selbstdiffusionskoeffizienten im Verlauf von Prozessen im Bereich der Lebensmittelverfahrenstechnik vorgestellt. Ausgehend von den physikalischen Grundlagen der Magnetresonanz werden verschiedene Anwendungen gezeigt, die das Potenzial besitzen, zum tieferen Verständnis der verfahrenstechnischen Prozesse beizutragen: Beispielhaft wird die Bestimmung von Wasserverteilungen bei der Rehydratation von getrockneten Proben, die Ermittlung von Temperaturverteilungen bei der Mikrowellenerwärmung und von beobachtungszeitabhängigen Selbstdiffusionskoeffizienten bei der Mikrowellen-Vakuumtrocknung gezeigt. Letztere können dazu genutzt werden, um weitere Aussagen über die innere Gewebestruktur wie Tortuosität und Porenradien zu erlangen. Applications of Magnetic Resonance for Investigating Water-, Temperature- and Poredistributions in Food Process Engineering Various methods of nuclear magnetic resonance (NMR) and their application for determinig water- and temperature distributions as well as self diffusion coefficients during food processing operations are presented. Starting from the physical basics of the magnetic resonance, various NMR applications are shown, which may contribute to a more comprehensive understanding of the food processes: Presented examples are the determination of water distributions during the rehydration of dried samples, of temperature distributions during a microwave heating process and of self diffusion coefficients during microwave vacuum drying. These observation time dependent self diffusion coefficients may be used to receive further information about the internal tissue structure, like tortuosity and pore radii. [source] | |||||||||||||||||||||||||