The Experts below are selected from a list of 309 Experts worldwide ranked by ideXlab platform
Athanasios I Liapis - One of the best experts on this subject based on the ideXlab platform.
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molecular based modeling and simulation studies of water water and water Macromolecule interactions in food and their effects on food dehydration
2013Co-Authors: Jee-ching Wang, Athanasios I LiapisAbstract:A molecular dynamics (MD) modeling and simulation approach has been developed to study porous food systems constructed with amylose chains. The results indicate that food Macromolecules form porous structures and can make the adjacent water molecules strongly bound with reduced water activity and removal rate by providing additional water–Macromolecule interactions that can significantly outweigh the reduction of the water–water interactions. These effects of pore structures are greater in systems with higher densities of food Macromolecules and smaller in size pores. During dehydration, water molecules can develop concave menisci in large pores and nonplanar interfaces between the dried and hydrated sections of the food, and thus water removal can be considered to start from the largest pores and, in particular, from the middle of the pores. Dehydration in general results in reduced pore sizes, a decreased number of pore openings, increased water–Macromolecule interactions, and reduced overall thermal conductivity, so that more heat and longer times are needed to further dehydrate the porous materials. Additionally, the average minimum entropy requirement for food dehydration is greater in food systems with higher densities of food Macromolecules and lower water content.
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Molecular-Based Modeling and Simulation Studies of Water–Water and Water–Macromolecule Interactions in Food and Their Effects on Food Dehydration
Food Engineering Series, 2013Co-Authors: Jee-ching Wang, Athanasios I LiapisAbstract:A molecular dynamics (MD) modeling and simulation approach has been developed to study porous food systems constructed with amylose chains. The results indicate that food Macromolecules form porous structures and can make the adjacent water molecules strongly bound with reduced water activity and removal rate by providing additional water–Macromolecule interactions that can significantly outweigh the reduction of the water–water interactions. These effects of pore structures are greater in systems with higher densities of food Macromolecules and smaller in size pores. During dehydration, water molecules can develop concave menisci in large pores and nonplanar interfaces between the dried and hydrated sections of the food, and thus water removal can be considered to start from the largest pores and, in particular, from the middle of the pores. Dehydration in general results in reduced pore sizes, a decreased number of pore openings, increased water–Macromolecule interactions, and reduced overall thermal conductivity, so that more heat and longer times are needed to further dehydrate the porous materials. Additionally, the average minimum entropy requirement for food dehydration is greater in food systems with higher densities of food Macromolecules and lower water content.
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Water–water and water–Macromolecule interactions in food dehydration and the effects of the pore structures of food on the energetics of the interactions
Journal of Food Engineering, 2012Co-Authors: Jee-ching Wang, Athanasios I LiapisAbstract:Abstract A molecular dynamics (MD) modeling and simulations approach has been rationally built and developed to study porous food systems constructed with amylose and dextran chains. The findings from our MD studies indicate that the presence of food Macromolecules decreases the energetics of the water–water interactions for the nearby water molecules in the pore space, but provides additional water–Macromolecule interactions that can significantly outweigh the partial loss of water–water interactions to make the adjacent water molecules strongly bound to the food Macromolecules so that the water activity and water removal rate are decreased as dehydration proceeds and, thus, the dehydration energy requirement would be increased. The effects of pore structures are greater in systems with higher densities of food Macromolecules, smaller in size pores, and stronger water–Macromolecule interactions. Dehydration of food materials can thus be reasonably expected to start from the largest pores and from the middle of the pores, and to have non-uniform water removal rates and non-planar water–vapor interfaces inside individual pores as well as across sections of the food materials. The food porous structures are found to have good pore connectivity for water molecules. As dehydration proceeds, water content and the support from water–water and water–Macromolecule interactions both decrease, causing the food porous structures to adopt more compact conformations and their main body to decrease in size. Dehydration in general also reduces pore sizes and the number of pore openings, increases the water–Macromolecule interactions, and leads to the reduction of the overall thermal conductivity of the system, so that more energy (heat), longer times, and/or greater temperature gradients are needed in order to further dehydrate the porous materials. Our thermodynamic analysis also shows that the average minimum entropy requirement for food dehydration is greater when the water–Macromolecule interactions are stronger and the food macromolecular density is higher. The importance of the physicochemical affinity of food molecules for water and of the compatibility of the resultant porous structures with water configurational structures in determining food properties and food processing through the water–Macromolecule interactions, is clearly and fundamentally verified by the results and discussion presented in this work.
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water water and water Macromolecule interactions in food dehydration and the effects of the pore structures of food on the energetics of the interactions
Journal of Food Engineering, 2012Co-Authors: Jee-ching Wang, Athanasios I LiapisAbstract:Abstract A molecular dynamics (MD) modeling and simulations approach has been rationally built and developed to study porous food systems constructed with amylose and dextran chains. The findings from our MD studies indicate that the presence of food Macromolecules decreases the energetics of the water–water interactions for the nearby water molecules in the pore space, but provides additional water–Macromolecule interactions that can significantly outweigh the partial loss of water–water interactions to make the adjacent water molecules strongly bound to the food Macromolecules so that the water activity and water removal rate are decreased as dehydration proceeds and, thus, the dehydration energy requirement would be increased. The effects of pore structures are greater in systems with higher densities of food Macromolecules, smaller in size pores, and stronger water–Macromolecule interactions. Dehydration of food materials can thus be reasonably expected to start from the largest pores and from the middle of the pores, and to have non-uniform water removal rates and non-planar water–vapor interfaces inside individual pores as well as across sections of the food materials. The food porous structures are found to have good pore connectivity for water molecules. As dehydration proceeds, water content and the support from water–water and water–Macromolecule interactions both decrease, causing the food porous structures to adopt more compact conformations and their main body to decrease in size. Dehydration in general also reduces pore sizes and the number of pore openings, increases the water–Macromolecule interactions, and leads to the reduction of the overall thermal conductivity of the system, so that more energy (heat), longer times, and/or greater temperature gradients are needed in order to further dehydrate the porous materials. Our thermodynamic analysis also shows that the average minimum entropy requirement for food dehydration is greater when the water–Macromolecule interactions are stronger and the food macromolecular density is higher. The importance of the physicochemical affinity of food molecules for water and of the compatibility of the resultant porous structures with water configurational structures in determining food properties and food processing through the water–Macromolecule interactions, is clearly and fundamentally verified by the results and discussion presented in this work.
Jee-ching Wang - One of the best experts on this subject based on the ideXlab platform.
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molecular based modeling and simulation studies of water water and water Macromolecule interactions in food and their effects on food dehydration
2013Co-Authors: Jee-ching Wang, Athanasios I LiapisAbstract:A molecular dynamics (MD) modeling and simulation approach has been developed to study porous food systems constructed with amylose chains. The results indicate that food Macromolecules form porous structures and can make the adjacent water molecules strongly bound with reduced water activity and removal rate by providing additional water–Macromolecule interactions that can significantly outweigh the reduction of the water–water interactions. These effects of pore structures are greater in systems with higher densities of food Macromolecules and smaller in size pores. During dehydration, water molecules can develop concave menisci in large pores and nonplanar interfaces between the dried and hydrated sections of the food, and thus water removal can be considered to start from the largest pores and, in particular, from the middle of the pores. Dehydration in general results in reduced pore sizes, a decreased number of pore openings, increased water–Macromolecule interactions, and reduced overall thermal conductivity, so that more heat and longer times are needed to further dehydrate the porous materials. Additionally, the average minimum entropy requirement for food dehydration is greater in food systems with higher densities of food Macromolecules and lower water content.
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Molecular-Based Modeling and Simulation Studies of Water–Water and Water–Macromolecule Interactions in Food and Their Effects on Food Dehydration
Food Engineering Series, 2013Co-Authors: Jee-ching Wang, Athanasios I LiapisAbstract:A molecular dynamics (MD) modeling and simulation approach has been developed to study porous food systems constructed with amylose chains. The results indicate that food Macromolecules form porous structures and can make the adjacent water molecules strongly bound with reduced water activity and removal rate by providing additional water–Macromolecule interactions that can significantly outweigh the reduction of the water–water interactions. These effects of pore structures are greater in systems with higher densities of food Macromolecules and smaller in size pores. During dehydration, water molecules can develop concave menisci in large pores and nonplanar interfaces between the dried and hydrated sections of the food, and thus water removal can be considered to start from the largest pores and, in particular, from the middle of the pores. Dehydration in general results in reduced pore sizes, a decreased number of pore openings, increased water–Macromolecule interactions, and reduced overall thermal conductivity, so that more heat and longer times are needed to further dehydrate the porous materials. Additionally, the average minimum entropy requirement for food dehydration is greater in food systems with higher densities of food Macromolecules and lower water content.
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Water–water and water–Macromolecule interactions in food dehydration and the effects of the pore structures of food on the energetics of the interactions
Journal of Food Engineering, 2012Co-Authors: Jee-ching Wang, Athanasios I LiapisAbstract:Abstract A molecular dynamics (MD) modeling and simulations approach has been rationally built and developed to study porous food systems constructed with amylose and dextran chains. The findings from our MD studies indicate that the presence of food Macromolecules decreases the energetics of the water–water interactions for the nearby water molecules in the pore space, but provides additional water–Macromolecule interactions that can significantly outweigh the partial loss of water–water interactions to make the adjacent water molecules strongly bound to the food Macromolecules so that the water activity and water removal rate are decreased as dehydration proceeds and, thus, the dehydration energy requirement would be increased. The effects of pore structures are greater in systems with higher densities of food Macromolecules, smaller in size pores, and stronger water–Macromolecule interactions. Dehydration of food materials can thus be reasonably expected to start from the largest pores and from the middle of the pores, and to have non-uniform water removal rates and non-planar water–vapor interfaces inside individual pores as well as across sections of the food materials. The food porous structures are found to have good pore connectivity for water molecules. As dehydration proceeds, water content and the support from water–water and water–Macromolecule interactions both decrease, causing the food porous structures to adopt more compact conformations and their main body to decrease in size. Dehydration in general also reduces pore sizes and the number of pore openings, increases the water–Macromolecule interactions, and leads to the reduction of the overall thermal conductivity of the system, so that more energy (heat), longer times, and/or greater temperature gradients are needed in order to further dehydrate the porous materials. Our thermodynamic analysis also shows that the average minimum entropy requirement for food dehydration is greater when the water–Macromolecule interactions are stronger and the food macromolecular density is higher. The importance of the physicochemical affinity of food molecules for water and of the compatibility of the resultant porous structures with water configurational structures in determining food properties and food processing through the water–Macromolecule interactions, is clearly and fundamentally verified by the results and discussion presented in this work.
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water water and water Macromolecule interactions in food dehydration and the effects of the pore structures of food on the energetics of the interactions
Journal of Food Engineering, 2012Co-Authors: Jee-ching Wang, Athanasios I LiapisAbstract:Abstract A molecular dynamics (MD) modeling and simulations approach has been rationally built and developed to study porous food systems constructed with amylose and dextran chains. The findings from our MD studies indicate that the presence of food Macromolecules decreases the energetics of the water–water interactions for the nearby water molecules in the pore space, but provides additional water–Macromolecule interactions that can significantly outweigh the partial loss of water–water interactions to make the adjacent water molecules strongly bound to the food Macromolecules so that the water activity and water removal rate are decreased as dehydration proceeds and, thus, the dehydration energy requirement would be increased. The effects of pore structures are greater in systems with higher densities of food Macromolecules, smaller in size pores, and stronger water–Macromolecule interactions. Dehydration of food materials can thus be reasonably expected to start from the largest pores and from the middle of the pores, and to have non-uniform water removal rates and non-planar water–vapor interfaces inside individual pores as well as across sections of the food materials. The food porous structures are found to have good pore connectivity for water molecules. As dehydration proceeds, water content and the support from water–water and water–Macromolecule interactions both decrease, causing the food porous structures to adopt more compact conformations and their main body to decrease in size. Dehydration in general also reduces pore sizes and the number of pore openings, increases the water–Macromolecule interactions, and leads to the reduction of the overall thermal conductivity of the system, so that more energy (heat), longer times, and/or greater temperature gradients are needed in order to further dehydrate the porous materials. Our thermodynamic analysis also shows that the average minimum entropy requirement for food dehydration is greater when the water–Macromolecule interactions are stronger and the food macromolecular density is higher. The importance of the physicochemical affinity of food molecules for water and of the compatibility of the resultant porous structures with water configurational structures in determining food properties and food processing through the water–Macromolecule interactions, is clearly and fundamentally verified by the results and discussion presented in this work.
Stefan O Trach - One of the best experts on this subject based on the ideXlab platform.
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estimation of Macromolecule concentrations and excluded volume effects for the cytoplasm of escherichia coli
Journal of Molecular Biology, 1991Co-Authors: Steven B Zimmerman, Stefan O TrachAbstract:The very high concentration of Macromolecules within cells can potentially have an overwhelming effect on the thermodynamic activity of cellular components because of excluded volume effects. To estimate the magnitudes of such effects, we have made an experimental study of the cytoplasm of Escherichia coli. Parameters from cells and cell extracts are used to calculate approximate activity coefficients for cytoplasmic conditions. These calculations require a representation of the sizes, concentrations and effective specific volumes of the Macromolecules in the extracts. Macromolecule size representations are obtained either by applying a two-phase distribution assay to define a related homogeneous solution or by using the molecular mass distribution of Macromolecules from gel filtration. Macromolecule concentrations in cytoplasm are obtained from analyses of extracts by applying a correction for the dilution that occurs during extraction. That factor is determined from experiments based upon the known impermeability of the cytoplasmic volume to sucrose in intact E. coli. Macromolecule concentrations in the cytoplasm of E. coli in either exponential or stationary growth phase are estimated to be ≈0.3 to 0.4 g/ml. Macromolecule specific volumes are inferred from the composition of close-packed precipitates induced by polyethylene glycol. Several well-characterized proteins which bind to DNA (lac repressor, RNA polymerase) are extremely sensitive to changes in salt concentration in studies in vitro, but are insensitive in studies in vivo. Application of the activity coefficients from the present work indicates that at least part of this discrepancy arises from the difference in excluded volumes in these studies. Applications of the activity coefficients to solubility or to association reactions are also discussed, as are changes associated with cell growth phase and osmotic or other effects. The use of solutions of purified Macromolecules that emulate the crowding conditions inferred for cytoplasm is discussed.
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estimation of Macromolecule concentrations and excluded volume effects for the cytoplasm of escherichia coli
Journal of Molecular Biology, 1991Co-Authors: Steven B Zimmerman, Stefan O TrachAbstract:The very high concentration of Macromolecules within cells can potentially have an overwhelming effect on the thermodynamic activity of cellular components because of excluded volume effects. To estimate the magnitudes of such effects, we have made an experimental study of the cytoplasm of Escherichia coli. Parameters from cells and cell extracts are used to calculate approximate activity coefficients for cytoplasmic conditions. These calculations require a representation of the sizes, concentrations and effective specific volumes of the Macromolecules in the extracts. Macromolecule size representations are obtained either by applying a two-phase distribution assay to define a related homogeneous solution or by using the molecular mass distribution of Macromolecules from gel filtration. Macromolecule concentrations in cytoplasm are obtained from analyses of extracts by applying a correction for the dilution that occurs during extraction. That factor is determined from experiments based upon the known impermeability of the cytoplasmic volume to sucrose in intact E. coli. Macromolecule concentrations in the cytoplasm of E. coli in either exponential or stationary growth phase are estimated to be approximately 0.3 to 0.4 g/ml. Macromolecule specific volumes are inferred from the composition of close-packed precipitates induced by polyethylene glycol. Several well-characterized proteins which bind to DNA (lac repressor, RNA polymerase) are extremely sensitive to changes in salt concentration in studies in vitro, but are insensitive in studies in vivo. Application of the activity coefficients from the present work indicates that at least part of this discrepancy arises from the difference in excluded volumes in these studies. Applications of the activity coefficients to solubility or to association reactions are also discussed, as are changes associated with cell growth phase and osmotic or other effects. The use of solutions of purified Macromolecules that emulate the crowding conditions inferred for cytoplasm is discussed.
Scott A Bradford - One of the best experts on this subject based on the ideXlab platform.
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Macromolecule mediated transport and retention of escherichia coli o157 h7 in saturated porous media
Water Research, 2010Co-Authors: Sharon L Walker, Scott A BradfordAbstract:The role of extracellular Macromolecules on Escherichia coli O157:H7 transport and retention was investigated in saturated porous media. To compare the relative transport and retention of E. coli cells that are Macromolecule rich and deficient, Macromolecules were partially cleaved using a proteolytic enzyme. Characterization of bacterial cell surfaces, cell aggregation, and experiments in a packed sand column were conducted over a range of ionic strength (IS). The results showed that Macromolecule-related interactions contribute to retention of E. coli O157:H7 and are strongly linked to solution IS. Under low IS conditions (IS � 0.1 mM), partial removal of the Macromolecules resulted in a more negative electrophoretic mobility of cells and created more unfavorable conditions for cell‐quartz and cell‐cell interactions as suggested by Derjaguin-Landau-Verwey-Overbeek (DLVO) interaction energy profiles and cell aggregation kinetics. Consequently, less retention was observed for enzyme treated cells in the corresponding column experiments. In addition, a time-dependent deposition process (i.e., ripening) was observed for untreated cells, but not for treated cells, supporting the fact that the Macromolecules enhanced cell‐cell interactions. Additional column experiments for untreated cells under favorable conditions (IS � 1 mM) showed that a significant amount of the cells were reversibly retained in the column, which contradicts predictions of DLVO theory. Furthermore, a non-monotonic cell retention profile was observed under favorable attachment conditions. These observations indicated that the presence of Macromolecules hindered irreversible interactions between the cells and the quartz surface. Published by Elsevier Ltd.
Steven B Zimmerman - One of the best experts on this subject based on the ideXlab platform.
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estimation of Macromolecule concentrations and excluded volume effects for the cytoplasm of escherichia coli
Journal of Molecular Biology, 1991Co-Authors: Steven B Zimmerman, Stefan O TrachAbstract:The very high concentration of Macromolecules within cells can potentially have an overwhelming effect on the thermodynamic activity of cellular components because of excluded volume effects. To estimate the magnitudes of such effects, we have made an experimental study of the cytoplasm of Escherichia coli. Parameters from cells and cell extracts are used to calculate approximate activity coefficients for cytoplasmic conditions. These calculations require a representation of the sizes, concentrations and effective specific volumes of the Macromolecules in the extracts. Macromolecule size representations are obtained either by applying a two-phase distribution assay to define a related homogeneous solution or by using the molecular mass distribution of Macromolecules from gel filtration. Macromolecule concentrations in cytoplasm are obtained from analyses of extracts by applying a correction for the dilution that occurs during extraction. That factor is determined from experiments based upon the known impermeability of the cytoplasmic volume to sucrose in intact E. coli. Macromolecule concentrations in the cytoplasm of E. coli in either exponential or stationary growth phase are estimated to be ≈0.3 to 0.4 g/ml. Macromolecule specific volumes are inferred from the composition of close-packed precipitates induced by polyethylene glycol. Several well-characterized proteins which bind to DNA (lac repressor, RNA polymerase) are extremely sensitive to changes in salt concentration in studies in vitro, but are insensitive in studies in vivo. Application of the activity coefficients from the present work indicates that at least part of this discrepancy arises from the difference in excluded volumes in these studies. Applications of the activity coefficients to solubility or to association reactions are also discussed, as are changes associated with cell growth phase and osmotic or other effects. The use of solutions of purified Macromolecules that emulate the crowding conditions inferred for cytoplasm is discussed.
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estimation of Macromolecule concentrations and excluded volume effects for the cytoplasm of escherichia coli
Journal of Molecular Biology, 1991Co-Authors: Steven B Zimmerman, Stefan O TrachAbstract:The very high concentration of Macromolecules within cells can potentially have an overwhelming effect on the thermodynamic activity of cellular components because of excluded volume effects. To estimate the magnitudes of such effects, we have made an experimental study of the cytoplasm of Escherichia coli. Parameters from cells and cell extracts are used to calculate approximate activity coefficients for cytoplasmic conditions. These calculations require a representation of the sizes, concentrations and effective specific volumes of the Macromolecules in the extracts. Macromolecule size representations are obtained either by applying a two-phase distribution assay to define a related homogeneous solution or by using the molecular mass distribution of Macromolecules from gel filtration. Macromolecule concentrations in cytoplasm are obtained from analyses of extracts by applying a correction for the dilution that occurs during extraction. That factor is determined from experiments based upon the known impermeability of the cytoplasmic volume to sucrose in intact E. coli. Macromolecule concentrations in the cytoplasm of E. coli in either exponential or stationary growth phase are estimated to be approximately 0.3 to 0.4 g/ml. Macromolecule specific volumes are inferred from the composition of close-packed precipitates induced by polyethylene glycol. Several well-characterized proteins which bind to DNA (lac repressor, RNA polymerase) are extremely sensitive to changes in salt concentration in studies in vitro, but are insensitive in studies in vivo. Application of the activity coefficients from the present work indicates that at least part of this discrepancy arises from the difference in excluded volumes in these studies. Applications of the activity coefficients to solubility or to association reactions are also discussed, as are changes associated with cell growth phase and osmotic or other effects. The use of solutions of purified Macromolecules that emulate the crowding conditions inferred for cytoplasm is discussed.
