The Experts below are selected from a list of 288 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.
J.d Kalenga Saka - One of the best experts on this subject based on the ideXlab platform.
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A solar air heater with composite-absorber systems for Food Dehydration
Renewable Energy, 2002Co-Authors: Amos Madhlopa, S.a Jones, J.d Kalenga SakaAbstract:Development of appropriate technologies for conversion of solar radiation to thermal energy is essential for Food preservation. A solar air heater, comprising two absorber systems in a single flat-plate collector, was designed on the principles of psychrometry. The heater was integrated to a drying chamber for Food Dehydration. This collector design offered flexibility in manual adjustment of the thermal characteristics of the solar dryer. The performance of the dryer was evaluated by drying fresh samples of mango (Mangifera indicus). Both fresh and dried mango samples were analysed for moisture content (MC), pH and ascorbic acid. During the Dehydration period, meteorological measurements were made. The air heater converted up to 21.3% of solar radiation to thermal power, and raised the temperature of the drying air from about 31.7 °C to 40.1 °C around noon. The dryer reduced the MC of sliced fresh mangoes from about 85% (w/w) to 13% (w/w) on wet basis, and retained 74% of ascorbic acid. It was found that the dryer was suitable for preservation of mangoes and other fresh Foods.
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A solar air heater with composite–absorber systems for Food Dehydration
Renewable Energy, 2002Co-Authors: Amos Madhlopa, S.a Jones, J.d Kalenga SakaAbstract:Development of appropriate technologies for conversion of solar radiation to thermal energy is essential for Food preservation. A solar air heater, comprising two absorber systems in a single flat-plate collector, was designed on the principles of psychrometry. The heater was integrated to a drying chamber for Food Dehydration. This collector design offered flexibility in manual adjustment of the thermal characteristics of the solar dryer. The performance of the dryer was evaluated by drying fresh samples of mango (Mangifera indicus). Both fresh and dried mango samples were analysed for moisture content (MC), pH and ascorbic acid. During the Dehydration period, meteorological measurements were made. The air heater converted up to 21.3% of solar radiation to thermal power, and raised the temperature of the drying air from about 31.7 °C to 40.1 °C around noon. The dryer reduced the MC of sliced fresh mangoes from about 85% (w/w) to 13% (w/w) on wet basis, and retained 74% of ascorbic acid. It was found that the dryer was suitable for preservation of mangoes and other fresh Foods.
D. Marinos-kouris - One of the best experts on this subject based on the ideXlab platform.
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Heat of sorption of water in dried fruits
International Journal of Food Science & Technology, 2007Co-Authors: Eleni Tsami, D. Marinos-kouris, Zacharias B. Maroulis, George SaravacosAbstract:Summary The heats of moisture adsorption and desorption in four dried fruits (sultana raisins, figs, prunes and apricots) were estimated from equilibrium sorption data, using the Clausius-Clapeyron equation in the temperature range 15–60°C. The net isosteric heat of sorption (qst) decreased sharply from about 20 kJ mol−1 water to near zero when the moisture content was increased from 0.05 to 0.50kg water kg−1 dry matter. An exponential function was fitted to the experimental qst values at various moisture contents (X), yielding two characteristic constants (q0 and X0) for each fruit. Mean and total heats of sorption were calculated from the proposed empirical equation, which are useful for enthalpy prediction in Food Dehydration. The heats of desorption were higher than the heats of adsorption, indicating significant hysteresis in the sorption of water, especially in dried apricots.
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Design of tray dryers for Food Dehydration
Journal of Food Engineering, 1997Co-Authors: Chris T. Kiranoudis, Zacharias B. Maroulis, D. Marinos-kouris, Michael TsamparlisAbstract:Abstract A mathematical model for the semi-batch operation of industrial dryers with trucks and trays is presented and analysed. Design aspects are discussed concerning problems involving both single dryer and systems of parallel dryers. In both cases, optimum flowsheet configuration and operation conditions are sought and verified by appropriate formulation of design and optimization strategies. The optimization objective is the total annual cost of the plant, subjected to constraints imposed by the operation of the dryer, thermodynamics, and construction reasoning. The decision variables were the number of trucks and the drying air stream humidity for each dryer involved, as well as the total number of dryers. The MINLP nature of the design problem required mathematical programming techniques for its solution. The optimization was carried out for a wide range of production capacities, and the optimal points, where a new truck or a new dryer is introduced, were evaluated. The effect of market economic figures on the design results is illustrated. The analysis focused on the design of two commercial agricultural products — namely, raisins and currants. A characteristic case study is presented in order to demonstrate the effectiveness of the proposed approach.
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Drying of solids: Selection of some continuous operation dryer types
Computers & Chemical Engineering, 1996Co-Authors: Chris T. Kiranoudis, Zacharias B. Maroulis, D. Marinos-kourisAbstract:Abstract Design and study of operational performance of convective industrial dryers are a strong indicator in the last stages of the selection procedure. This problem is addressed in a straightforward way for the three most popular types; conveyor-belt, fluidized bed and rotary dryers. Design was carried out by appropriately optimizing the total annual cost of each configuration for a given production capacity. All dryer types were compared explicitely by evaluating optimal configurations for a wide range of production capacity values. Once the dryer configuration is specified, its optimal operational performance was evaluated by comparing the optimum operational cost versus production capacity for predefined optimal designed structures. Rotary dryers turned to be rather expensive compared to fluidized bed dryers, regarding design. On operational grounds, however, it is the other way around due to the understandably favored heat transfer achieved in rotary dryers. Conveyor-belt dryers, when utilized, lie somewhere in between producing satisfactory results both on design and on operational grounds. A characteristic example of Food Dehydration process is included, to demonstrate the effectiveness of the proposed approach.
Enrique Riera - One of the best experts on this subject based on the ideXlab platform.
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Airborne power ultrasonic systems for Food Dehydration processes intensification
2018Co-Authors: Roque Rubén Andrés García, Alberto Pinto, Víctor M. Acosta, Enrique RieraAbstract:Process intensification constitutes a high interesting and promising industrial area. It aims to modify conventional processes or develop new technologies in order to reduce energy needs, increase yields and improve product quality. When drying at low temperature, heat degradation is diminish, although long drying times may induce quality losses and involve high operating costs. It has been demonstrated by this research group (CSIC) that power ultrasound have a great potential in Food drying processes. The effects associated with the application of power ultrasound (turbulence, diffusion, acoustic streaming, etc.) can enhance heat and mass transfer and may constitute a way for process intensification. In order to produce the desired effects in the Food samples, the ultrasonic system has to generate an intense ultrasonic field with high amplitude levels. These requirements may lead the system to work in a nonlinear regime, both in the generation process (frequency shifts, hysteresis, etc.) and in the acoustic propagation through the gas medium (shock waves, harmonics, etc.). The ultrasonic system, in charge of the generation this specific acoustic field, has to be designed in order to have a resonant mode behavior with a high quality factor and narrow bandwidth. This system is based on a Langevin-type transducer, a mechanical amplifier and an extensive radiator that allows a good impedance matching with the medium, large amplitude of vibration, and high directional beams for energy concentration. The aim of this work is to introduce an ultrasonic system that fulfils those requirements, considering the whole process composed by the numerical simulation using finite element models (FEM), the dynamic and acoustic characterization
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Modal analysis and nonlinear characterization of an airborne power ultrasonic transducer with rectangular plate radiator.
Ultrasonics, 2017Co-Authors: Roque Rubén Andrés, Víctor M. Acosta, Margaret Lucas, Enrique RieraAbstract:Some industrial processes like particle agglomeration or Food Dehydration among others can be enhanced by the use of power ultrasonic technologies. These technologies are based on an airborne power ultrasonic transducer (APUT) constituted by a pre-stressed Langevin-type transducer, a mechanical amplifier and an extensive plate radiator. In order to produce the desired effects in industrial processing, the transducer has to vibrate in an extensional mode driving an extensive radiator in the desired flexural mode with high amplitude displacements. Due to the generation of these high amplitude displacements in the radiator surfaces, non-linear effects like frequency shifts, hysteresis or modal interactions, among others, may be produced in the transducer behavior. When any nonlinear effect appears, when applying power, the stability and efficiency of this ultrasonic technology decreases, and the transducer may be damaged depending on the excitation power level and the nature of the nonlinearity. In this paper, an APUT with flat rectangular radiator is presented, as the active part of an innovative system with stepped reflectors. The nonlinear behavior of the APUT has been characterized numerically and experimentally in case of the modal analysis and experimentally in the case of dynamic analysis. According to the results obtained after the experiments, no modal interactions are expected, nor do other nonlinear effects.
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Ultrasonic field generated by different airborne power ultrasonic transducers with extensive radiators
2017Co-Authors: Roque R. Andrés, Víctor M. Acosta Rodríguez, Enrique RieraAbstract:Industrial processes like Food Dehydration, particle agglomeration or supercritical oil extraction, among others may be enhanced when assisted by airborne power ultrasound. Currently, there is a wide range of airborne power ultrasonic transducers designed for specific uses in fluids to enhance different industrial applications. The main types of such transducers may be classified as cylindrical, circular and rectangular plate radiators that generate ultrasonic fields suitable for different applications and show different advantages and disadvantages. This work deals with the generation and measurement of acoustic fields of different airborne power ultrasonic systems designed for diverse industrial applications operating under different boundary conditions.
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Description of an ultrasonic technology for Food Dehydration process intensification
2016Co-Authors: Roque R. Andrés, Enrique Riera, Alfonso Blanco Blanco, Ángel GuinotAbstract:Food Dehydration processes assisted by power ultrasound constitute an efficient and green technology. In order to obtain good results with this technology it is necessary to take into account several aspects regarding the ultrasonic generation by a power ultrasonic transducer, the energy propagation in the fluid media and absorption in the samples. Ultrasonic waves produce different effects when propagating through a medium, like an increase in mass transport kinetics, and others related to the so called sponge effect and cavitation. This kind of process needs the whole system to work in a power regime. This may imply the appearance of non-linear effects in the transducer behavior and in the acoustic field generated inside the Dehydration chamber. This paper describes this technology, paying special attention to the numerical design and the dynamic and modal characterization of the power ultrasonic transducer. As a conclusion, neither modal interaction nor any other non-linear effect, apart from a slight ...