Ashim Datta | Cornell University (original) (raw)

Papers by Ashim Datta

Journal of Food Engineering, 2007

Physical properties of breads during baking were measured using three different heating modes of ... more Physical properties of breads during baking were measured using three different heating modes of microwave plus infrared (MIR), microwave plus jet impingement (MJET) and jet impingement (JET) in two different commercially available microwave combination ovens. Breads baked in JET oven were significantly different from the breads baked in other ovens with respect to their specific volume and moisture content. Transient values of dielectric constant, dielectric loss factor, specific bulk volume, porosity, thermal conductivity and moisture content were determined. For all heating modes, thermal conductivity and dielectric properties of breads decreased sharply within the first 2-3 min of baking and then remained constant. Regression equations were developed to relate these properties to moisture content and porosity changes during baking.

Journal of Food Engineering, 2007

The nature of pore spaces in breads baked using various heating modes (microwave-infrared (MIR), ... more The nature of pore spaces in breads baked using various heating modes (microwave-infrared (MIR), microwave-jet impingement (MJET) and jet impingement (JET)) were characterized in terms of total porosity, fraction of closed, blind and flow-through pores, and pore size distributions using several novel and old techniques (liquid extrusion porosimetry, scanned image analysis, pycnometry, volume displacement method and scanning electron microscopy or SEM). For the breads studies here, a very significant pore size distribution exists covering diameters of a few microns to several thousand microns. It appears that the pore size distribution is bimodal and only a combination of techniques can provide comprehensive information, i.e., any one technique cannot cover the large range of pore size, total porosity and flow-through vs. closed pores. A significant fraction of the pores was found to be closed. Breads baked in JET had the highest total porosity followed by MJET and MIR. Other measurements on breads baked in JET also lay on one end of the spectrum (either smallest or largest), which is consistent with SEM pictures where JET baked breads looked quite different from the ones baked in other ovens.

Transport in Porous Media, 2010

... In many practical applications, swelling systems can be unsatu-rated, eg, in the case of dryi... more ... In many practical applications, swelling systems can be unsatu-rated, eg, in the case of drying of wood and food materials (Datta 2007; Perre and Turner 1999), and transport in soils (Carminati et al. 2008; Purandara et al. 2008). ...

Food and Bioproducts Processing, 1999

A multiphase porous media model has been developed to predict the moisture migration, oil uptake ... more A multiphase porous media model has been developed to predict the moisture migration, oil uptake and energy transport in a food material such as a semi-dry potato during deep-fat frying. The model predictions are validated using experimental data from the literature. Spatial moisture pro les show two distinctive regions (dry or crust region near the surface and wet region in most of the core) with a sharp interface which can be referred to as the evaporation front. Spatial temperature pro les show two distinctive regions -higher but constant temperature gradient region near the surface, and lower temperature gradient region in the core. In the crust region, vapour diffusional ux is comparable with vapour convective ux. In the more moist core region, capillary ux of liquid water is comparable to the convective ux of liquid water. Therefore, all three modes of transport -diffusional, capillarity, and pressure driven (Darcy) ow are found to be important. Sensitivity of the nal product moisture and temperature to changes in oil temperature, initial moisture content of the sample, thickness of the sample, and the surface heat and mass transfer coef cients are discussed.

Transport in Porous Media, 2010

A thermomechanical theory for multiphase transport in unsaturated swelling porous media is develo... more A thermomechanical theory for multiphase transport in unsaturated swelling porous media is developed on the basis of Hybrid Mixture Theory (saturated systems can also be modeled as a special case of this general theory). The aim is to comprehensively and non-empirically describe the effect of viscoelastic deformation on fluid transport (and vice versa) for swelling porous materials. Three phases are considered in the system: the swelling solid matrix s, liquid l, and air a. The Coleman–Noll procedure is used to obtain the restrictions on the form of the constitutive equations. The form of Darcy’s law for the fluid phase, which takes into account both Fickian and non-Fickian transport, is slightly different from the forms obtained by other researchers though all the terms have been included. When the fluid phases interact with the swelling solid porous matrix, deformation occurs. Viscoelastic large deformation of the solid matrix is investigated. A simple form of differential-integral equation is obtained for the fluid transport under isothermal conditions, which can be coupled with the deformation of the solid matrix to solve for transport in an unsaturated system. The modeling theory thus developed, which involves two-way coupling of the viscoelastic solid deformation and fluid transport, can be applied to study the processing of biopolymers, for example, soaking of foodstuffs and stress-crack predictions. Moreover, extension and modification of this modeling theory can be applied to study a vast variety of problems, such as drying of gels, consolidation of clays, drug delivery, and absorption of liquids in diapers.

Aiche Journal, 2009

The 3D nongray radiative heat exchange in a near-infrared commercial oven is modeled. The spectru... more The 3D nongray radiative heat exchange in a near-infrared commercial oven is modeled. The spectrum is divided into into four gray bands to model the narrow wavelength range in which the halogen heat source radiates, the wavelength dependence of the food surface emittance, and the absorption coefficient of the heat source cover glass. The model is used to estimate the heating of a cuboidal food sample for 1 min at different cyclic settings of a halogen radiant heat source. The model predictions agree with the experimental data, and capture the cover-glass and the food-surface temperature and heat flux histories very well. The band-wise distribution of energy absorption by the food reveals the separate contributions from the source and the oven walls. Comparison of the heating rates between the measured non-gray food-surface and the different gray food-surface emittance values establishes the necessity of the nongray treatment. © 2009 American Institute of Chemical Engineers AIChE J, 2009

Journal of Biomechanical Engineering-transactions of The Asme, 2008

Computational model for airflow through the upper airway of a horse was developed. Previous flow ... more Computational model for airflow through the upper airway of a horse was developed. Previous flow models for human airway do not hold true for horses due to significant differences in anatomy and the high Reynolds number of flow in the equine airway. Moreover, models that simulate the entire respiratory cycle and emphasize on pressures inside the airway in relation to various anatomical diseases are lacking. The geometry of the airway was created by reconstructing images obtained from computed tomography scans of a thoroughbred racehorse. Different geometries for inhalation and exhalation were used for the model based on the difference in the nasopharynx size during the two phases of respiration. The Reynolds averaged Navier-Stokes equations were solved for the isothermal flow with the standard k-epsilon model for turbulence. Transient pressure boundary conditions for the entire breathing cycle were obtained from past experimental studies on live horses. The flow equations were solved in a commercial finite volume solver. The flow rates, computed based on the applied pressure conditions, were compared to experimentally measured flow rates for model validation. Detailed analysis of velocity, pressure, and turbulence characteristics of the flow was done. Velocity magnitudes at various slices during inhalation were found to be higher than corresponding velocity magnitudes during exhalation. The front and middle parts of the nasopharynx were found to have minimum intraluminal pressure in the airway during inhalation. During exhalation, the pressures in the soft palate were higher compared to those in the larynx, epiglottis, and nasopharynx. Turbulent kinetic energy was found to be maximum at the entry to the airway and gradually decreased as the flow moved inside the airway. However, turbulent kinetic energy increased in regions of the airway with abrupt change in area. Based on the analysis of pressure distribution at different sections of the airway, it was concluded that the front part of the nasopharynx requires maximum muscular activity to support it during inhalation. During exhalation, the soft palate is susceptible to displacements due to presence of high pressures. These can serve as critical information for diagnosis and treatment planning of diseases known to affect the soft palate and nasopharynx in horses, and can potentially be useful for human beings.

Journal of Physical Chemistry B, 2008

Many microorganisms such as bacteria and fungi possess so-called capsules made of polysaccharides... more Many microorganisms such as bacteria and fungi possess so-called capsules made of polysaccharides which protect these microorganisms from environmental insults and host immune defenses. The polysaccharide capsule of C. neoformans, a human pathogenic yeast, is capable of self assembly, composed mostly of glucuronoxylomannan (GXM), a polysaccharide with molecular weight of approximately 2,000,000 Da and has several layers with different densities. The objective of this study was to model pore-hindered diffusion and binding of the GXM-specific antibody within the C. neoformans capsule. Using the finite element method (FEM), we created a model which represents the in vivo binding of GXM-specific antibody to a C. neoformans cell taking into account the intravenous infusion time of antibody, antibody diffusion through capsular pores, and Michaelis-Menten kinetics of antibody binding to capsular GXM. The model predicted rapid diffusion of antibody to all regions of the capsule where pore size was greater than the Stokes diameter of the antibody. Binding occurred primarily at intermediate regions of the capsule. The GXM concentration in each capsular region was the principal determinant of the steady-state antibody-GXM complex concentration, while the forward binding rate constant influenced the rate of complex formation in each region. The concentration profiles predicted by the model closely matched experimental immunofluorescence data. Inclusion of different antibody isotypes (IgG, IgA and IgM) into the modeling algorithm resulted in similar complex formation in outer capsular regions, but different depth of binding at inner regions. These results have implications for the development of new antibody-based therapies.

Journal of Food Engineering, 2007

Physical properties of breads during baking were measured using three different heating modes of ... more Physical properties of breads during baking were measured using three different heating modes of microwave plus infrared (MIR), microwave plus jet impingement (MJET) and jet impingement (JET) in two different commercially available microwave combination ovens. Breads baked in JET oven were significantly different from the breads baked in other ovens with respect to their specific volume and moisture content. Transient values of dielectric constant, dielectric loss factor, specific bulk volume, porosity, thermal conductivity and moisture content were determined. For all heating modes, thermal conductivity and dielectric properties of breads decreased sharply within the first 2-3 min of baking and then remained constant. Regression equations were developed to relate these properties to moisture content and porosity changes during baking.

Journal of Food Engineering, 2007

The nature of pore spaces in breads baked using various heating modes (microwave-infrared (MIR), ... more The nature of pore spaces in breads baked using various heating modes (microwave-infrared (MIR), microwave-jet impingement (MJET) and jet impingement (JET)) were characterized in terms of total porosity, fraction of closed, blind and flow-through pores, and pore size distributions using several novel and old techniques (liquid extrusion porosimetry, scanned image analysis, pycnometry, volume displacement method and scanning electron microscopy or SEM). For the breads studies here, a very significant pore size distribution exists covering diameters of a few microns to several thousand microns. It appears that the pore size distribution is bimodal and only a combination of techniques can provide comprehensive information, i.e., any one technique cannot cover the large range of pore size, total porosity and flow-through vs. closed pores. A significant fraction of the pores was found to be closed. Breads baked in JET had the highest total porosity followed by MJET and MIR. Other measurements on breads baked in JET also lay on one end of the spectrum (either smallest or largest), which is consistent with SEM pictures where JET baked breads looked quite different from the ones baked in other ovens.

Chemical Engineering Science, 2011

A comprehensive poromechanics-based modeling framework that can be used to model transport and de... more A comprehensive poromechanics-based modeling framework that can be used to model transport and deformation in food materials under a variety of processing conditions and states (rubbery or glassy) has been developed. Simplifications to the model equations have been developed, based on driving forces for deformation (moisture change and gas pressure development) and on the state of food material for transport. The framework is applied to two completely different food processes (contact heating of hamburger patties and drying of potatoes). The modeling framework is implemented using total Lagrangian mesh for solid momentum balance and Eulerian mesh for transport equations, and validated using experimental data. Transport in liquid phase dominates for both the processes, with hamburger patty shrinking with moisture loss for all moisture contents, while shrinkage in potato stops below a critical moisture content.

Drying Technology, 2012

Multiphase transport model to simulate drying of honeycomb ceramic substrates in a conventional (... more Multiphase transport model to simulate drying of honeycomb ceramic substrates in a conventional (hot air) drier is developed. Heat and moisture transport in the honeycomb walls as well as channels is modeled. The model predictions are validated against experiments done for drying of cylinder-shaped substrates by comparing histories and axial profiles of moisture loss and point temperature histories at various locations. Drying experiments are performed at two different values of air temperature, 103°C and 137°C, at a relative humidity value of 5%. Sensitivity analysis reveals that the drying process is controlled by heat and water vapor transport. External heat transfer is the dominant resistance mechanism for energy transport, whereas internal convection and binary diffusion dominate the resistance to vapor transport.

Food and Bioproducts Processing

Multiphase transport models of food processes require surface heat and mass transfer coefficients... more Multiphase transport models of food processes require surface heat and mass transfer coefficients as boundary conditions that are traditionally assumed. A conjugate heat and mass transfer model is solved for simple microwave heating of food as a porous medium (from which vapor blows out) with air flow over it, such that there is no need to provide the boundary conditions at the food-air interface. Surface fluxes due to diffusion and flow (blowing) are computed for both vapor and heat from which transfer coefficients are obtained. As evaporation increases with heating, vapor flux due to pressure-driven flow increases but remains small compared with diffusive flux. Vapor accumulation at the interface increases the diffusive flux, leading to an 8% increase in mass transfer coefficient.

Journal of Food Engineering, 2011

Computer-aided engineering tools can help speed up food product, process and equipment design by ... more Computer-aided engineering tools can help speed up food product, process and equipment design by making it easier to check ''what if'' scenarios, much as such tools have improved productivity in other industries. In particular, food safety is a critical area where such predictive tools can have great impact. A realistic, integrated and comprehensive software has been developed that can simulate a food process and its safety by combining a fundamental, physics-based model of the process with the kinetics of microbiological and chemical changes during processing to provide needed information at any time and at any location in the food during processing. Compositions for a large number of foods are integrated into the software, and therefore, composition-based prediction of thermophysical properties, needed for the model, can be obtained. Microbiological and chemical kinetic databases that are also built-in can cover many practical situations, based on the grouping of foods. An intuitive graphical user interface has been built with those in the food sector in mind.

Journal of Food Safety, 2000

Journal of Food Science, 2010

Abstract: The objective of this study was to use an existing database of food products and their... more Abstract: The objective of this study was to use an existing database of food products and their associated processes, link it with a list of the foodborne pathogenic microorganisms associated with those products and finally identify growth and inactivation kinetic parameters associated with those pathogens. The database was to be used as a part of the development of comprehensive software which could predict food safety and quality for any food product. The main issues in building such a predictive system included selection of predictive models, associations of different food types with pathogens (as determined from outbreak histories), and variability in data from different experiments. More than 1000 data sets from published literature were analyzed and grouped according to microorganisms and food types. Final grouping of data consisted of the 8 most prevalent pathogens for 14 different food groups, covering all of the foods (>7000) listed in the USDA Natl. Nutrient Database. Data for each group were analyzed in terms of 1st-order inactivation, 1st-order growth, and sigmoidal growth models, and their kinetic response for growth and inactivation as a function of temperature were reported. Means and 95% confidence intervals were calculated for prediction equations. The primary advantage in obtaining group-specific kinetic data is the ability to extend microbiological growth and death simulation to a large array of product and process possibilities, while still being reasonably accurate. Such simulation capability could provide vital ‘‘what if’’ scenarios for industry, Extension, and academia in food safety.

Comprehensive Reviews in Food Science and Food Safety, 2008

This article is part of a collection entitled “Models for Safety, Quality, and Competitiveness of... more This article is part of a collection entitled “Models for Safety, Quality, and Competitiveness of the Food Processing Sector,” published in Comprehensive Reviews in Food Science and Food Safety. It has been peer-reviewed and was written as a follow-up of a pre-IFT workshop, partially funded by the USDA NRI grant 2005-35503-16208.

Journal of Food Engineering, 2007

Physical properties of breads during baking were measured using three different heating modes of ... more Physical properties of breads during baking were measured using three different heating modes of microwave plus infrared (MIR), microwave plus jet impingement (MJET) and jet impingement (JET) in two different commercially available microwave combination ovens. Breads baked in JET oven were significantly different from the breads baked in other ovens with respect to their specific volume and moisture content. Transient values of dielectric constant, dielectric loss factor, specific bulk volume, porosity, thermal conductivity and moisture content were determined. For all heating modes, thermal conductivity and dielectric properties of breads decreased sharply within the first 2-3 min of baking and then remained constant. Regression equations were developed to relate these properties to moisture content and porosity changes during baking.

Journal of Food Engineering, 2007

The nature of pore spaces in breads baked using various heating modes (microwave-infrared (MIR), ... more The nature of pore spaces in breads baked using various heating modes (microwave-infrared (MIR), microwave-jet impingement (MJET) and jet impingement (JET)) were characterized in terms of total porosity, fraction of closed, blind and flow-through pores, and pore size distributions using several novel and old techniques (liquid extrusion porosimetry, scanned image analysis, pycnometry, volume displacement method and scanning electron microscopy or SEM). For the breads studies here, a very significant pore size distribution exists covering diameters of a few microns to several thousand microns. It appears that the pore size distribution is bimodal and only a combination of techniques can provide comprehensive information, i.e., any one technique cannot cover the large range of pore size, total porosity and flow-through vs. closed pores. A significant fraction of the pores was found to be closed. Breads baked in JET had the highest total porosity followed by MJET and MIR. Other measurements on breads baked in JET also lay on one end of the spectrum (either smallest or largest), which is consistent with SEM pictures where JET baked breads looked quite different from the ones baked in other ovens.

Transport in Porous Media, 2010

... In many practical applications, swelling systems can be unsatu-rated, eg, in the case of dryi... more ... In many practical applications, swelling systems can be unsatu-rated, eg, in the case of drying of wood and food materials (Datta 2007; Perre and Turner 1999), and transport in soils (Carminati et al. 2008; Purandara et al. 2008). ...

Food and Bioproducts Processing, 1999

A multiphase porous media model has been developed to predict the moisture migration, oil uptake ... more A multiphase porous media model has been developed to predict the moisture migration, oil uptake and energy transport in a food material such as a semi-dry potato during deep-fat frying. The model predictions are validated using experimental data from the literature. Spatial moisture pro les show two distinctive regions (dry or crust region near the surface and wet region in most of the core) with a sharp interface which can be referred to as the evaporation front. Spatial temperature pro les show two distinctive regions -higher but constant temperature gradient region near the surface, and lower temperature gradient region in the core. In the crust region, vapour diffusional ux is comparable with vapour convective ux. In the more moist core region, capillary ux of liquid water is comparable to the convective ux of liquid water. Therefore, all three modes of transport -diffusional, capillarity, and pressure driven (Darcy) ow are found to be important. Sensitivity of the nal product moisture and temperature to changes in oil temperature, initial moisture content of the sample, thickness of the sample, and the surface heat and mass transfer coef cients are discussed.

Transport in Porous Media, 2010

A thermomechanical theory for multiphase transport in unsaturated swelling porous media is develo... more A thermomechanical theory for multiphase transport in unsaturated swelling porous media is developed on the basis of Hybrid Mixture Theory (saturated systems can also be modeled as a special case of this general theory). The aim is to comprehensively and non-empirically describe the effect of viscoelastic deformation on fluid transport (and vice versa) for swelling porous materials. Three phases are considered in the system: the swelling solid matrix s, liquid l, and air a. The Coleman–Noll procedure is used to obtain the restrictions on the form of the constitutive equations. The form of Darcy’s law for the fluid phase, which takes into account both Fickian and non-Fickian transport, is slightly different from the forms obtained by other researchers though all the terms have been included. When the fluid phases interact with the swelling solid porous matrix, deformation occurs. Viscoelastic large deformation of the solid matrix is investigated. A simple form of differential-integral equation is obtained for the fluid transport under isothermal conditions, which can be coupled with the deformation of the solid matrix to solve for transport in an unsaturated system. The modeling theory thus developed, which involves two-way coupling of the viscoelastic solid deformation and fluid transport, can be applied to study the processing of biopolymers, for example, soaking of foodstuffs and stress-crack predictions. Moreover, extension and modification of this modeling theory can be applied to study a vast variety of problems, such as drying of gels, consolidation of clays, drug delivery, and absorption of liquids in diapers.

Aiche Journal, 2009

The 3D nongray radiative heat exchange in a near-infrared commercial oven is modeled. The spectru... more The 3D nongray radiative heat exchange in a near-infrared commercial oven is modeled. The spectrum is divided into into four gray bands to model the narrow wavelength range in which the halogen heat source radiates, the wavelength dependence of the food surface emittance, and the absorption coefficient of the heat source cover glass. The model is used to estimate the heating of a cuboidal food sample for 1 min at different cyclic settings of a halogen radiant heat source. The model predictions agree with the experimental data, and capture the cover-glass and the food-surface temperature and heat flux histories very well. The band-wise distribution of energy absorption by the food reveals the separate contributions from the source and the oven walls. Comparison of the heating rates between the measured non-gray food-surface and the different gray food-surface emittance values establishes the necessity of the nongray treatment. © 2009 American Institute of Chemical Engineers AIChE J, 2009

Journal of Biomechanical Engineering-transactions of The Asme, 2008

Computational model for airflow through the upper airway of a horse was developed. Previous flow ... more Computational model for airflow through the upper airway of a horse was developed. Previous flow models for human airway do not hold true for horses due to significant differences in anatomy and the high Reynolds number of flow in the equine airway. Moreover, models that simulate the entire respiratory cycle and emphasize on pressures inside the airway in relation to various anatomical diseases are lacking. The geometry of the airway was created by reconstructing images obtained from computed tomography scans of a thoroughbred racehorse. Different geometries for inhalation and exhalation were used for the model based on the difference in the nasopharynx size during the two phases of respiration. The Reynolds averaged Navier-Stokes equations were solved for the isothermal flow with the standard k-epsilon model for turbulence. Transient pressure boundary conditions for the entire breathing cycle were obtained from past experimental studies on live horses. The flow equations were solved in a commercial finite volume solver. The flow rates, computed based on the applied pressure conditions, were compared to experimentally measured flow rates for model validation. Detailed analysis of velocity, pressure, and turbulence characteristics of the flow was done. Velocity magnitudes at various slices during inhalation were found to be higher than corresponding velocity magnitudes during exhalation. The front and middle parts of the nasopharynx were found to have minimum intraluminal pressure in the airway during inhalation. During exhalation, the pressures in the soft palate were higher compared to those in the larynx, epiglottis, and nasopharynx. Turbulent kinetic energy was found to be maximum at the entry to the airway and gradually decreased as the flow moved inside the airway. However, turbulent kinetic energy increased in regions of the airway with abrupt change in area. Based on the analysis of pressure distribution at different sections of the airway, it was concluded that the front part of the nasopharynx requires maximum muscular activity to support it during inhalation. During exhalation, the soft palate is susceptible to displacements due to presence of high pressures. These can serve as critical information for diagnosis and treatment planning of diseases known to affect the soft palate and nasopharynx in horses, and can potentially be useful for human beings.

Journal of Physical Chemistry B, 2008

Many microorganisms such as bacteria and fungi possess so-called capsules made of polysaccharides... more Many microorganisms such as bacteria and fungi possess so-called capsules made of polysaccharides which protect these microorganisms from environmental insults and host immune defenses. The polysaccharide capsule of C. neoformans, a human pathogenic yeast, is capable of self assembly, composed mostly of glucuronoxylomannan (GXM), a polysaccharide with molecular weight of approximately 2,000,000 Da and has several layers with different densities. The objective of this study was to model pore-hindered diffusion and binding of the GXM-specific antibody within the C. neoformans capsule. Using the finite element method (FEM), we created a model which represents the in vivo binding of GXM-specific antibody to a C. neoformans cell taking into account the intravenous infusion time of antibody, antibody diffusion through capsular pores, and Michaelis-Menten kinetics of antibody binding to capsular GXM. The model predicted rapid diffusion of antibody to all regions of the capsule where pore size was greater than the Stokes diameter of the antibody. Binding occurred primarily at intermediate regions of the capsule. The GXM concentration in each capsular region was the principal determinant of the steady-state antibody-GXM complex concentration, while the forward binding rate constant influenced the rate of complex formation in each region. The concentration profiles predicted by the model closely matched experimental immunofluorescence data. Inclusion of different antibody isotypes (IgG, IgA and IgM) into the modeling algorithm resulted in similar complex formation in outer capsular regions, but different depth of binding at inner regions. These results have implications for the development of new antibody-based therapies.

Journal of Food Engineering, 2007

Physical properties of breads during baking were measured using three different heating modes of ... more Physical properties of breads during baking were measured using three different heating modes of microwave plus infrared (MIR), microwave plus jet impingement (MJET) and jet impingement (JET) in two different commercially available microwave combination ovens. Breads baked in JET oven were significantly different from the breads baked in other ovens with respect to their specific volume and moisture content. Transient values of dielectric constant, dielectric loss factor, specific bulk volume, porosity, thermal conductivity and moisture content were determined. For all heating modes, thermal conductivity and dielectric properties of breads decreased sharply within the first 2-3 min of baking and then remained constant. Regression equations were developed to relate these properties to moisture content and porosity changes during baking.

Journal of Food Engineering, 2007

The nature of pore spaces in breads baked using various heating modes (microwave-infrared (MIR), ... more The nature of pore spaces in breads baked using various heating modes (microwave-infrared (MIR), microwave-jet impingement (MJET) and jet impingement (JET)) were characterized in terms of total porosity, fraction of closed, blind and flow-through pores, and pore size distributions using several novel and old techniques (liquid extrusion porosimetry, scanned image analysis, pycnometry, volume displacement method and scanning electron microscopy or SEM). For the breads studies here, a very significant pore size distribution exists covering diameters of a few microns to several thousand microns. It appears that the pore size distribution is bimodal and only a combination of techniques can provide comprehensive information, i.e., any one technique cannot cover the large range of pore size, total porosity and flow-through vs. closed pores. A significant fraction of the pores was found to be closed. Breads baked in JET had the highest total porosity followed by MJET and MIR. Other measurements on breads baked in JET also lay on one end of the spectrum (either smallest or largest), which is consistent with SEM pictures where JET baked breads looked quite different from the ones baked in other ovens.

Chemical Engineering Science, 2011

A comprehensive poromechanics-based modeling framework that can be used to model transport and de... more A comprehensive poromechanics-based modeling framework that can be used to model transport and deformation in food materials under a variety of processing conditions and states (rubbery or glassy) has been developed. Simplifications to the model equations have been developed, based on driving forces for deformation (moisture change and gas pressure development) and on the state of food material for transport. The framework is applied to two completely different food processes (contact heating of hamburger patties and drying of potatoes). The modeling framework is implemented using total Lagrangian mesh for solid momentum balance and Eulerian mesh for transport equations, and validated using experimental data. Transport in liquid phase dominates for both the processes, with hamburger patty shrinking with moisture loss for all moisture contents, while shrinkage in potato stops below a critical moisture content.

Drying Technology, 2012

Multiphase transport model to simulate drying of honeycomb ceramic substrates in a conventional (... more Multiphase transport model to simulate drying of honeycomb ceramic substrates in a conventional (hot air) drier is developed. Heat and moisture transport in the honeycomb walls as well as channels is modeled. The model predictions are validated against experiments done for drying of cylinder-shaped substrates by comparing histories and axial profiles of moisture loss and point temperature histories at various locations. Drying experiments are performed at two different values of air temperature, 103°C and 137°C, at a relative humidity value of 5%. Sensitivity analysis reveals that the drying process is controlled by heat and water vapor transport. External heat transfer is the dominant resistance mechanism for energy transport, whereas internal convection and binary diffusion dominate the resistance to vapor transport.

Food and Bioproducts Processing

Multiphase transport models of food processes require surface heat and mass transfer coefficients... more Multiphase transport models of food processes require surface heat and mass transfer coefficients as boundary conditions that are traditionally assumed. A conjugate heat and mass transfer model is solved for simple microwave heating of food as a porous medium (from which vapor blows out) with air flow over it, such that there is no need to provide the boundary conditions at the food-air interface. Surface fluxes due to diffusion and flow (blowing) are computed for both vapor and heat from which transfer coefficients are obtained. As evaporation increases with heating, vapor flux due to pressure-driven flow increases but remains small compared with diffusive flux. Vapor accumulation at the interface increases the diffusive flux, leading to an 8% increase in mass transfer coefficient.

Journal of Food Engineering, 2011

Computer-aided engineering tools can help speed up food product, process and equipment design by ... more Computer-aided engineering tools can help speed up food product, process and equipment design by making it easier to check ''what if'' scenarios, much as such tools have improved productivity in other industries. In particular, food safety is a critical area where such predictive tools can have great impact. A realistic, integrated and comprehensive software has been developed that can simulate a food process and its safety by combining a fundamental, physics-based model of the process with the kinetics of microbiological and chemical changes during processing to provide needed information at any time and at any location in the food during processing. Compositions for a large number of foods are integrated into the software, and therefore, composition-based prediction of thermophysical properties, needed for the model, can be obtained. Microbiological and chemical kinetic databases that are also built-in can cover many practical situations, based on the grouping of foods. An intuitive graphical user interface has been built with those in the food sector in mind.

Journal of Food Safety, 2000

Journal of Food Science, 2010

Abstract: The objective of this study was to use an existing database of food products and their... more Abstract: The objective of this study was to use an existing database of food products and their associated processes, link it with a list of the foodborne pathogenic microorganisms associated with those products and finally identify growth and inactivation kinetic parameters associated with those pathogens. The database was to be used as a part of the development of comprehensive software which could predict food safety and quality for any food product. The main issues in building such a predictive system included selection of predictive models, associations of different food types with pathogens (as determined from outbreak histories), and variability in data from different experiments. More than 1000 data sets from published literature were analyzed and grouped according to microorganisms and food types. Final grouping of data consisted of the 8 most prevalent pathogens for 14 different food groups, covering all of the foods (>7000) listed in the USDA Natl. Nutrient Database. Data for each group were analyzed in terms of 1st-order inactivation, 1st-order growth, and sigmoidal growth models, and their kinetic response for growth and inactivation as a function of temperature were reported. Means and 95% confidence intervals were calculated for prediction equations. The primary advantage in obtaining group-specific kinetic data is the ability to extend microbiological growth and death simulation to a large array of product and process possibilities, while still being reasonably accurate. Such simulation capability could provide vital ‘‘what if’’ scenarios for industry, Extension, and academia in food safety.

Comprehensive Reviews in Food Science and Food Safety, 2008

This article is part of a collection entitled “Models for Safety, Quality, and Competitiveness of... more This article is part of a collection entitled “Models for Safety, Quality, and Competitiveness of the Food Processing Sector,” published in Comprehensive Reviews in Food Science and Food Safety. It has been peer-reviewed and was written as a follow-up of a pre-IFT workshop, partially funded by the USDA NRI grant 2005-35503-16208.