Martin Okos - Academia.edu (original) (raw)

Papers by Martin Okos

Research paper thumbnail of The production of chemicals from food processing wastes using a novel fermenter separator

A range of chemicals can be made from fermentation processes, and most fermentations are characte... more A range of chemicals can be made from fermentation processes, and most fermentations are characterized by product inhibition. As product concentration increases, inhibitory products can substantially limit the rate of fermentation processes. Product recovery costs are a strong function of concentration. It is expensive to recover low levels of product from a fermentation broth. Thus, fermentation costs (which increase with higher product concentration) traditionally must be balanced against product recovery costs (which decrease with product concentration). A novel reactor-separator process has been developed at Purdue University to minimize product inhibition of fermentation rates. This reactor has been shown to exhibit very high productivities --- simultaneously producing and removing a inhibitory product while maintaining a high viable cell concentration in the reactor. The basic objective of this study is to develop an energy efficient and economical process to convert food wastes to usable fuels and chemicals. The work is divided into two major efforts: an applied phase which involves design and building of a whey to ethanol process as well as process design and optimization; and a basic phase which involves investigating alternative fermentation systems and fundamental research on immobilized cell reactor systems. This document discusses the study and its results.

Research paper thumbnail of The production of chemicals from food processing wastes using a novel fermenter separator: Seventh quarterly report, March 1, 1989--May 31, 1989

Fermentation costs (which increase with higher product concentration) traditionally must be balan... more Fermentation costs (which increase with higher product concentration) traditionally must be balanced against product recovery costs (which decrease with product concentration). A novel reactor-separator process has been developed at Purdue University to minimize product inhibition of fermentation rates. This has been shown to exhibit very high productivities -- simultaneously producing and removing a inhibitory product while maintaining a high viable cell concentration in the reactor. The objective of this study is to develop an energy efficient and economical process to convert food wastes to usable chemicals. Work is divided into two major effects (1) an applied phase which involves design and building a whey to ethanol process as well as process design and optimization and (2) a basic phase which involves investigating alternative fermentation systems and fundamental research on immobilized cell reactor systems. Accomplishments are discussed.

Research paper thumbnail of Physicochemical characterization of changes in pea protein as the result of cold extrusion

Research paper thumbnail of Model-Based Analysis of IGF-1 Effect on Osteoblast and Osteoclast Regulation in Bone Turnover

Journal of Biological Systems, 2016

The main determinant of bone Ca accretion is a bimolecular regulatory network on osteoblast (OB) ... more The main determinant of bone Ca accretion is a bimolecular regulatory network on osteoblast (OB) and osteoclast (OC). Even though IGF-1 is known as an important regulator in bone cell cycle, little has been done to model IGF-1 action in bone cell regulation. Thus, the objective is to develop a mathematical model that depicts the regulatory action of IGF-1 onto the OB and OC interaction, and to evaluate adolescent and adult bone Ca accretion in response to differences in IGF-1 levels. As a result, a dynamic model of OB and OC with two main regulatory systems, i.e., Receptor Activator for Nuclear Factor [Formula: see text]B (RANK)-RANK Ligand (RANKL)-osteoprogerin (OPG) system, and TGF-[Formula: see text], was augmented with the IGF-1, and incorporated into Ca kinetic data to predict exchangeable bone Ca. The developed model could predict a change in OB and OC levels in response to perturbations in regulators, producing results consistent with bone physiology and published experimenta...

Research paper thumbnail of Optimization of Oil Extraction of Soy Flour Using Mini Extrusion Technology

Mini extrusion technology is a relatively new technology that offers fast timing and processing o... more Mini extrusion technology is a relatively new technology that offers fast timing and processing of food products. This technology paired with the advantageous properties and growing demand for soybeans can lead to a larger span of uses for the extruder that have not yet been explored, including NASA space missions and incorporation of soybeans into developing countries. During past research on parameters of operation, it was discovered that a significant amount of oil was being separated from the soy meal at the die of the mini extruder. Maximum removal of this oil allows use of the soy meal and soy oil to be maximized, and further, may allow reduction in chemical methods of oil removal being currently used in industry.

Research paper thumbnail of Immobilized cell reactor-separator with simultaneous product separation and methods for design and use thereof

Research paper thumbnail of A Theoretical Modeling for Suggesting Unique Mechanism of Adolescent Calcium Metabolism

Research paper thumbnail of The Evolution of Biological Engineering

International Journal of Engineering Education

The discipline of Biological Engineering is an academic structure evolving to address educational... more The discipline of Biological Engineering is an academic structure evolving to address educational needs based on technologies arising from the new advances in the life sciences. This paper focuses on presenting concepts that distinguish Biological Engineering as a discipline, distinct from existing engineering disciplines, based on unique principles that define biology/living systems. It presents a perspective of Biological Engineering that focuses on the engineering of the inherent, central principles of living systems versus the application of externally engineered systems to existing living systems to alter their behavior or structure. Important concepts in educational curricular topics and concepts are also discussed, along with the historical background to the development of Agricultural Engineering into Biological Engineering.

Research paper thumbnail of Conversion of food processing wastes into ethanol using a novel biological reactor/separator. Final report, September 1, 1984September 30, 1985

This project deals with scaling up and operating a novel Immobilized Cell Reactor-Separator (ICRS... more This project deals with scaling up and operating a novel Immobilized Cell Reactor-Separator (ICRS) developed at Purdue University. This reactor uses gas flow through an immobilized cell reactor to remove a volatile product (ethanol) from the fermentation broth. It was found that the life and performance of a small scale reactor could run continuously - 24 hours/day - for a

Research paper thumbnail of Sustainable food processing systems - Path to a zero discharge: reduction of water, waste and energy

Procedia Food Science, 2011

Since food processing systems consume extensive amounts of water and energy, the food industry ha... more Since food processing systems consume extensive amounts of water and energy, the food industry has the incentive to reduce water and energy with the goal of developing a zero discharge process that utilizes substantially less water and energy, and generates no waste. The objective of this study is to evaluate water/energy consumption and to propose alternatives that reduce water and energy in the processing of three food products; 1) edible bean, 2) dairy products, and 3) corn masa. Three main approaches were; 1) plant-scale audit data collection to determine energy consumption, 2) laboratory scale experiments to assess product quality changes with a reduction in water and energy usage, and 3) computer-aided simulation to design systems for reduced water and energy consumption and wastewater generation. The results suggest that a zero discharge process is feasible by reducing water and energy. Modifications to the edible bean process reduced water input up to 55% and wastewater generation was decreased up to 91%. In dairy plant, the optimal heat recovery option could economically decrease the boiler fuel requirement by 50 times, and reduce the operating cost to 2.7% of the present cost. The water reuse process in redesigned corn masa process could reduce 90% of wastewater and 55% of water usage compared to the traditional process. The amount of energy required for heating was saved by 70% in the water reuse process. When scaling-up to plant-scale, reusing water could reduce water consumption by 95% and reduce energy requirement by about 80%.

Research paper thumbnail of Kinetic model of growth and lactic acid production from lactose by Lactobacillus bulgaricus

Process Biochemistry, 1993

Batch and continuous fermentation kinetics of Lactobacillus bulgaricus were examined in detail. T... more Batch and continuous fermentation kinetics of Lactobacillus bulgaricus were examined in detail. The batch kinetic model includes the effect of pH, lactate and substrate. The effect ofpH on the enzyme /3galactosidase is reflected in the value of pu,ll,, the Monad's growth constant. Empirical expressions to estimate model parameters based on pH were established. These werehrther used to estimate the ceil mass and lactic acid concentration for the fermentation proceeded with no pH control. At high pH lactic acid was mostly formed by growth associated mechanisms and at IowpH it was due to the cell maintenance. The relationship between ATP concentration and cell mass in a batch fermentation could be approximated by a Leudeking-Piret like relationship. The continuous fermentation was studied with valyingpH and initial substrate conditions. A maximum productivity of 6.2 gjlitre per hour was obtained atpH 56 for the CSTR system, which was three times the productivity obtained for a batch system at the same PH. The CSTR system had a high productivity over a very small range of retention times. Three stages were found to he sufficient to utilize completely the lactose, but at the cost of decreasing the productivity to 48 g/litre per hour.

Research paper thumbnail of The production of chemicals from food processing wastes using a novel fermenter separator. Annual progress report, January 1993--March 1994

any of their employees, makes any warranty, express or implied, or assumes any legal liability or... more any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefUlness of any information, apparatus, product or process disclosed or represents that its use would not infringe privately,owned rights. _ __ _ DIS"I1RIIRITtON OF THt6 DOCUMENT IS UNLI IT Table of Contents '

Research paper thumbnail of Computer Aided Engineering in the Food Industry

Food Properties and Computer-Aided Engineering of Food Processing Systems, 1989

The potential areas for use of computer-aided engineering in the food industry are enormous and r... more The potential areas for use of computer-aided engineering in the food industry are enormous and range from the design, to the operation of intergrated food processing systems. Computers can allow the food scientist and the food engineer to systematically and efficiently select from a myriad of alternatives the most effective design or operational mode of a process. As an example, once the food scientist has, through the use of the computer, developed the optimal formulation, the food engineer will, also with the aid of the computer, design the optimal processing system to manufacture the product. After the plant has been designed and constructed, plant management can then use the computer to schedule, operate, and control for the optimal production of the food product The tasks of formulation, design and operation, will be linked together with a common data base to allow the efficient transfer of information from product development through to production.

Research paper thumbnail of Use of solar energy in the concentration of liquid foods

Research paper thumbnail of Modeling pharmaceutical compacts tensile strength based on viscoelastic properties

Powder Technology, 2013

ABSTRACT Although several researchers acknowledge the effects of viscoelasticity in pharmaceutica... more ABSTRACT Although several researchers acknowledge the effects of viscoelasticity in pharmaceutical powder compaction, no models have been reported that relate compact mechanical properties to the powder viscoelastic properties. The tensile strength of a compact is largely influenced by contact area between deforming particles which depends on the viscoelastic properties and compaction variables. The objective of this research was to develop semi-mechanistic models based on viscoelastic contact area estimates, to predict tensile strength of Microcrystalline Cellulose (MCC) and Acetaminophen (APAP) compacts. Formulations with varying amounts of MCC, APAP and moisture contents corresponding to 50 and 70% RH were prepared. The powders were compressed in a Uniaxial testing machine (Instron) at a punch velocity of 2 mm/min to final pressures in the range of 12.5 to 44 MPa. The diametral tensile strength, compaction and viscoelastic properties were determined. The deformation contact area was estimated using equation by Lum and Duncan-Hewitt [22] based on the median particle size of MCC, compaction and viscoelastic properties as determined from the Maxwell model. It was found that the estimated contact area depended on the APAP composition, moisture content and on compaction pressure. The viscoelastic contact area, density and final compact tensile strength were found to increase with increasing compaction pressure, moisture content and MCC. A unified model that expresses the compact tensile strength as a function of viscoelastic contact area was successfully developed.

Research paper thumbnail of Improved Line Heat Source Thermal Conductivity Probe

Journal of Food Science, 1981

ABSTRACTAn improved line heat source thermal conductivity probe was made to simplify the construc... more ABSTRACTAn improved line heat source thermal conductivity probe was made to simplify the construction and extend the life of thermal conductivity probes. The accuracy of thermal conductivity measurement is also improved. The better linearity of temperature versus logarithm of time was obtained as compared to published techniques. The probe made with the heater wire and thermocouple on the outside of a sewing needle instead of inside of a hypodermic needle was checked by measuring the thermal conductivity of known samples. Results obtained with the improved probe show lower temperature rise and lower standard deviation.

Research paper thumbnail of Effect of Cooking on the Thermal Conductivity of Whole and Ground Lean Beef

Journal of Food Science, 1981

ABSTRACTThe probe method was used to measure thermal conductivity of beef through a temperature r... more ABSTRACTThe probe method was used to measure thermal conductivity of beef through a temperature range of 30–120°C. Thermal conductivity of beef increases with temperature up to 70°C followed by a decrease during the denaturation of proteins and subsequent loss of water. The thermal conductivity of beef again increases with temperature after protein denaturation. The thermal conductivity of cooked beef is lower than raw beef up to about 80°C. The rate of increase for cooked meat thermal conductivity is fairly constant with temperature at a given moisture content. Models based on composition and temperature were found to predict the thermal conductivity of meat during cooking at an average standard percent error of 7%.

Research paper thumbnail of Hydrolysis of Lactose in Acid Whey Using Β‐Galactosidase Adsorbed to a Phenol Formaldehyde Resin

Journal of Food Science, 1978

ABSTRACTThe feasibility of using immobilized enzymes for the commercial hydrolysis of lactose in ... more ABSTRACTThe feasibility of using immobilized enzymes for the commercial hydrolysis of lactose in acid whey was investigated. The areas of enzyme kinetics, enzyme adsorption, mass transfer, reactor design and economics were considered. All reaction studies were carried out at 40°C, pH 4. Adsorption of β‐galactosidase into a porous phenol formaldehyde resin (Duolite ES‐762) followed an S‐shaped isotherm at low concentrations and adsorption increased with temperature at 0, 24 and 26°C. Up to 0.6g of Wallerstein enzyme preparation (4043 activity units) were adsorbed to 1g of dry resin. Adsorption had little effect on enzyme activity. An integral reactor of immobilized β‐galactosidase retained nearly full activity for over 120 days of continual hydrolysis of lactose in acid whey and pure lactose solutions. Throughout the long term study, mold was effectively inhibited by the use of 0.1% w/v of potassium sorbate and CO2. Based on 120‐day catalyst life and the integral reactor data for Duo...

Research paper thumbnail of Effect of porosity on moisture diffusion during drying of pasta

Journal of Food Engineering, 1996

Heat and mass transfer studies were conducted with pasta cylinders at different porosities, tempe... more Heat and mass transfer studies were conducted with pasta cylinders at different porosities, temperatures and pressures. Tests with pasta cylinders were conducted at porosities of 6 and 2670, temperatures of 40, 55, 71 and 105°C and total pressures of 77, 101 and 202 kPa. Analysis of tests conducted with 3.18, 4.76 and 5.56 mm diameter dense pasta cylinders (670 porosity) at 71°C indicated that mass transfer was consistent with control by internal diffusion. The drying characteristics of dense samples were not affected by total pressure, suggesting that the mechanism of internal moisture movement is best considered a liquid or adsorbed phase diffusion phenomenon. Effective moisture diffusivities of dense pasta increased as temperature and moisture content increased, with values ranging from 8 to 106 x 10-I' m'ls. Diffusivities of porous pasta (26% porosity) ranged from 36 to 221 x IO-'2 m'ls. Heat transfer studies with dense and porous pasta indicated that the center temperature for 5.56 mm diameter pasta cylinders approached the dry bulb air temperature within 3°C in less than 10 min, supporting the assumption that pasta drying can be considered an isothermal process. A semi-empirical model for moisture difjfusivity in pasta that accounts for the effects of porosi& pressure and moisture binding was

Research paper thumbnail of Kinetics of nonenzymatic browning in dried skim milk

Journal of Food Engineering, 1990

Water activity Reference water activity Constant parameters Concentration of brown pigment (OD/g)... more Water activity Reference water activity Constant parameters Concentration of brown pigment (OD/g) Solid content ("Brix) Activation energy (kcal/mol) Rate constant (OD/g d) Arrhenius frequency factor Moisture content (g &O/g dry solids) Universal gas law constant (kcal/mol K) Time (days) Absolute temperature (K)

Research paper thumbnail of The production of chemicals from food processing wastes using a novel fermenter separator

A range of chemicals can be made from fermentation processes, and most fermentations are characte... more A range of chemicals can be made from fermentation processes, and most fermentations are characterized by product inhibition. As product concentration increases, inhibitory products can substantially limit the rate of fermentation processes. Product recovery costs are a strong function of concentration. It is expensive to recover low levels of product from a fermentation broth. Thus, fermentation costs (which increase with higher product concentration) traditionally must be balanced against product recovery costs (which decrease with product concentration). A novel reactor-separator process has been developed at Purdue University to minimize product inhibition of fermentation rates. This reactor has been shown to exhibit very high productivities --- simultaneously producing and removing a inhibitory product while maintaining a high viable cell concentration in the reactor. The basic objective of this study is to develop an energy efficient and economical process to convert food wastes to usable fuels and chemicals. The work is divided into two major efforts: an applied phase which involves design and building of a whey to ethanol process as well as process design and optimization; and a basic phase which involves investigating alternative fermentation systems and fundamental research on immobilized cell reactor systems. This document discusses the study and its results.

Research paper thumbnail of The production of chemicals from food processing wastes using a novel fermenter separator: Seventh quarterly report, March 1, 1989--May 31, 1989

Fermentation costs (which increase with higher product concentration) traditionally must be balan... more Fermentation costs (which increase with higher product concentration) traditionally must be balanced against product recovery costs (which decrease with product concentration). A novel reactor-separator process has been developed at Purdue University to minimize product inhibition of fermentation rates. This has been shown to exhibit very high productivities -- simultaneously producing and removing a inhibitory product while maintaining a high viable cell concentration in the reactor. The objective of this study is to develop an energy efficient and economical process to convert food wastes to usable chemicals. Work is divided into two major effects (1) an applied phase which involves design and building a whey to ethanol process as well as process design and optimization and (2) a basic phase which involves investigating alternative fermentation systems and fundamental research on immobilized cell reactor systems. Accomplishments are discussed.

Research paper thumbnail of Physicochemical characterization of changes in pea protein as the result of cold extrusion

Research paper thumbnail of Model-Based Analysis of IGF-1 Effect on Osteoblast and Osteoclast Regulation in Bone Turnover

Journal of Biological Systems, 2016

The main determinant of bone Ca accretion is a bimolecular regulatory network on osteoblast (OB) ... more The main determinant of bone Ca accretion is a bimolecular regulatory network on osteoblast (OB) and osteoclast (OC). Even though IGF-1 is known as an important regulator in bone cell cycle, little has been done to model IGF-1 action in bone cell regulation. Thus, the objective is to develop a mathematical model that depicts the regulatory action of IGF-1 onto the OB and OC interaction, and to evaluate adolescent and adult bone Ca accretion in response to differences in IGF-1 levels. As a result, a dynamic model of OB and OC with two main regulatory systems, i.e., Receptor Activator for Nuclear Factor [Formula: see text]B (RANK)-RANK Ligand (RANKL)-osteoprogerin (OPG) system, and TGF-[Formula: see text], was augmented with the IGF-1, and incorporated into Ca kinetic data to predict exchangeable bone Ca. The developed model could predict a change in OB and OC levels in response to perturbations in regulators, producing results consistent with bone physiology and published experimenta...

Research paper thumbnail of Optimization of Oil Extraction of Soy Flour Using Mini Extrusion Technology

Mini extrusion technology is a relatively new technology that offers fast timing and processing o... more Mini extrusion technology is a relatively new technology that offers fast timing and processing of food products. This technology paired with the advantageous properties and growing demand for soybeans can lead to a larger span of uses for the extruder that have not yet been explored, including NASA space missions and incorporation of soybeans into developing countries. During past research on parameters of operation, it was discovered that a significant amount of oil was being separated from the soy meal at the die of the mini extruder. Maximum removal of this oil allows use of the soy meal and soy oil to be maximized, and further, may allow reduction in chemical methods of oil removal being currently used in industry.

Research paper thumbnail of Immobilized cell reactor-separator with simultaneous product separation and methods for design and use thereof

Research paper thumbnail of A Theoretical Modeling for Suggesting Unique Mechanism of Adolescent Calcium Metabolism

Research paper thumbnail of The Evolution of Biological Engineering

International Journal of Engineering Education

The discipline of Biological Engineering is an academic structure evolving to address educational... more The discipline of Biological Engineering is an academic structure evolving to address educational needs based on technologies arising from the new advances in the life sciences. This paper focuses on presenting concepts that distinguish Biological Engineering as a discipline, distinct from existing engineering disciplines, based on unique principles that define biology/living systems. It presents a perspective of Biological Engineering that focuses on the engineering of the inherent, central principles of living systems versus the application of externally engineered systems to existing living systems to alter their behavior or structure. Important concepts in educational curricular topics and concepts are also discussed, along with the historical background to the development of Agricultural Engineering into Biological Engineering.

Research paper thumbnail of Conversion of food processing wastes into ethanol using a novel biological reactor/separator. Final report, September 1, 1984September 30, 1985

This project deals with scaling up and operating a novel Immobilized Cell Reactor-Separator (ICRS... more This project deals with scaling up and operating a novel Immobilized Cell Reactor-Separator (ICRS) developed at Purdue University. This reactor uses gas flow through an immobilized cell reactor to remove a volatile product (ethanol) from the fermentation broth. It was found that the life and performance of a small scale reactor could run continuously - 24 hours/day - for a

Research paper thumbnail of Sustainable food processing systems - Path to a zero discharge: reduction of water, waste and energy

Procedia Food Science, 2011

Since food processing systems consume extensive amounts of water and energy, the food industry ha... more Since food processing systems consume extensive amounts of water and energy, the food industry has the incentive to reduce water and energy with the goal of developing a zero discharge process that utilizes substantially less water and energy, and generates no waste. The objective of this study is to evaluate water/energy consumption and to propose alternatives that reduce water and energy in the processing of three food products; 1) edible bean, 2) dairy products, and 3) corn masa. Three main approaches were; 1) plant-scale audit data collection to determine energy consumption, 2) laboratory scale experiments to assess product quality changes with a reduction in water and energy usage, and 3) computer-aided simulation to design systems for reduced water and energy consumption and wastewater generation. The results suggest that a zero discharge process is feasible by reducing water and energy. Modifications to the edible bean process reduced water input up to 55% and wastewater generation was decreased up to 91%. In dairy plant, the optimal heat recovery option could economically decrease the boiler fuel requirement by 50 times, and reduce the operating cost to 2.7% of the present cost. The water reuse process in redesigned corn masa process could reduce 90% of wastewater and 55% of water usage compared to the traditional process. The amount of energy required for heating was saved by 70% in the water reuse process. When scaling-up to plant-scale, reusing water could reduce water consumption by 95% and reduce energy requirement by about 80%.

Research paper thumbnail of Kinetic model of growth and lactic acid production from lactose by Lactobacillus bulgaricus

Process Biochemistry, 1993

Batch and continuous fermentation kinetics of Lactobacillus bulgaricus were examined in detail. T... more Batch and continuous fermentation kinetics of Lactobacillus bulgaricus were examined in detail. The batch kinetic model includes the effect of pH, lactate and substrate. The effect ofpH on the enzyme /3galactosidase is reflected in the value of pu,ll,, the Monad's growth constant. Empirical expressions to estimate model parameters based on pH were established. These werehrther used to estimate the ceil mass and lactic acid concentration for the fermentation proceeded with no pH control. At high pH lactic acid was mostly formed by growth associated mechanisms and at IowpH it was due to the cell maintenance. The relationship between ATP concentration and cell mass in a batch fermentation could be approximated by a Leudeking-Piret like relationship. The continuous fermentation was studied with valyingpH and initial substrate conditions. A maximum productivity of 6.2 gjlitre per hour was obtained atpH 56 for the CSTR system, which was three times the productivity obtained for a batch system at the same PH. The CSTR system had a high productivity over a very small range of retention times. Three stages were found to he sufficient to utilize completely the lactose, but at the cost of decreasing the productivity to 48 g/litre per hour.

Research paper thumbnail of The production of chemicals from food processing wastes using a novel fermenter separator. Annual progress report, January 1993--March 1994

any of their employees, makes any warranty, express or implied, or assumes any legal liability or... more any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefUlness of any information, apparatus, product or process disclosed or represents that its use would not infringe privately,owned rights. _ __ _ DIS"I1RIIRITtON OF THt6 DOCUMENT IS UNLI IT Table of Contents '

Research paper thumbnail of Computer Aided Engineering in the Food Industry

Food Properties and Computer-Aided Engineering of Food Processing Systems, 1989

The potential areas for use of computer-aided engineering in the food industry are enormous and r... more The potential areas for use of computer-aided engineering in the food industry are enormous and range from the design, to the operation of intergrated food processing systems. Computers can allow the food scientist and the food engineer to systematically and efficiently select from a myriad of alternatives the most effective design or operational mode of a process. As an example, once the food scientist has, through the use of the computer, developed the optimal formulation, the food engineer will, also with the aid of the computer, design the optimal processing system to manufacture the product. After the plant has been designed and constructed, plant management can then use the computer to schedule, operate, and control for the optimal production of the food product The tasks of formulation, design and operation, will be linked together with a common data base to allow the efficient transfer of information from product development through to production.

Research paper thumbnail of Use of solar energy in the concentration of liquid foods

Research paper thumbnail of Modeling pharmaceutical compacts tensile strength based on viscoelastic properties

Powder Technology, 2013

ABSTRACT Although several researchers acknowledge the effects of viscoelasticity in pharmaceutica... more ABSTRACT Although several researchers acknowledge the effects of viscoelasticity in pharmaceutical powder compaction, no models have been reported that relate compact mechanical properties to the powder viscoelastic properties. The tensile strength of a compact is largely influenced by contact area between deforming particles which depends on the viscoelastic properties and compaction variables. The objective of this research was to develop semi-mechanistic models based on viscoelastic contact area estimates, to predict tensile strength of Microcrystalline Cellulose (MCC) and Acetaminophen (APAP) compacts. Formulations with varying amounts of MCC, APAP and moisture contents corresponding to 50 and 70% RH were prepared. The powders were compressed in a Uniaxial testing machine (Instron) at a punch velocity of 2 mm/min to final pressures in the range of 12.5 to 44 MPa. The diametral tensile strength, compaction and viscoelastic properties were determined. The deformation contact area was estimated using equation by Lum and Duncan-Hewitt [22] based on the median particle size of MCC, compaction and viscoelastic properties as determined from the Maxwell model. It was found that the estimated contact area depended on the APAP composition, moisture content and on compaction pressure. The viscoelastic contact area, density and final compact tensile strength were found to increase with increasing compaction pressure, moisture content and MCC. A unified model that expresses the compact tensile strength as a function of viscoelastic contact area was successfully developed.

Research paper thumbnail of Improved Line Heat Source Thermal Conductivity Probe

Journal of Food Science, 1981

ABSTRACTAn improved line heat source thermal conductivity probe was made to simplify the construc... more ABSTRACTAn improved line heat source thermal conductivity probe was made to simplify the construction and extend the life of thermal conductivity probes. The accuracy of thermal conductivity measurement is also improved. The better linearity of temperature versus logarithm of time was obtained as compared to published techniques. The probe made with the heater wire and thermocouple on the outside of a sewing needle instead of inside of a hypodermic needle was checked by measuring the thermal conductivity of known samples. Results obtained with the improved probe show lower temperature rise and lower standard deviation.

Research paper thumbnail of Effect of Cooking on the Thermal Conductivity of Whole and Ground Lean Beef

Journal of Food Science, 1981

ABSTRACTThe probe method was used to measure thermal conductivity of beef through a temperature r... more ABSTRACTThe probe method was used to measure thermal conductivity of beef through a temperature range of 30–120°C. Thermal conductivity of beef increases with temperature up to 70°C followed by a decrease during the denaturation of proteins and subsequent loss of water. The thermal conductivity of beef again increases with temperature after protein denaturation. The thermal conductivity of cooked beef is lower than raw beef up to about 80°C. The rate of increase for cooked meat thermal conductivity is fairly constant with temperature at a given moisture content. Models based on composition and temperature were found to predict the thermal conductivity of meat during cooking at an average standard percent error of 7%.

Research paper thumbnail of Hydrolysis of Lactose in Acid Whey Using Β‐Galactosidase Adsorbed to a Phenol Formaldehyde Resin

Journal of Food Science, 1978

ABSTRACTThe feasibility of using immobilized enzymes for the commercial hydrolysis of lactose in ... more ABSTRACTThe feasibility of using immobilized enzymes for the commercial hydrolysis of lactose in acid whey was investigated. The areas of enzyme kinetics, enzyme adsorption, mass transfer, reactor design and economics were considered. All reaction studies were carried out at 40°C, pH 4. Adsorption of β‐galactosidase into a porous phenol formaldehyde resin (Duolite ES‐762) followed an S‐shaped isotherm at low concentrations and adsorption increased with temperature at 0, 24 and 26°C. Up to 0.6g of Wallerstein enzyme preparation (4043 activity units) were adsorbed to 1g of dry resin. Adsorption had little effect on enzyme activity. An integral reactor of immobilized β‐galactosidase retained nearly full activity for over 120 days of continual hydrolysis of lactose in acid whey and pure lactose solutions. Throughout the long term study, mold was effectively inhibited by the use of 0.1% w/v of potassium sorbate and CO2. Based on 120‐day catalyst life and the integral reactor data for Duo...

Research paper thumbnail of Effect of porosity on moisture diffusion during drying of pasta

Journal of Food Engineering, 1996

Heat and mass transfer studies were conducted with pasta cylinders at different porosities, tempe... more Heat and mass transfer studies were conducted with pasta cylinders at different porosities, temperatures and pressures. Tests with pasta cylinders were conducted at porosities of 6 and 2670, temperatures of 40, 55, 71 and 105°C and total pressures of 77, 101 and 202 kPa. Analysis of tests conducted with 3.18, 4.76 and 5.56 mm diameter dense pasta cylinders (670 porosity) at 71°C indicated that mass transfer was consistent with control by internal diffusion. The drying characteristics of dense samples were not affected by total pressure, suggesting that the mechanism of internal moisture movement is best considered a liquid or adsorbed phase diffusion phenomenon. Effective moisture diffusivities of dense pasta increased as temperature and moisture content increased, with values ranging from 8 to 106 x 10-I' m'ls. Diffusivities of porous pasta (26% porosity) ranged from 36 to 221 x IO-'2 m'ls. Heat transfer studies with dense and porous pasta indicated that the center temperature for 5.56 mm diameter pasta cylinders approached the dry bulb air temperature within 3°C in less than 10 min, supporting the assumption that pasta drying can be considered an isothermal process. A semi-empirical model for moisture difjfusivity in pasta that accounts for the effects of porosi& pressure and moisture binding was

Research paper thumbnail of Kinetics of nonenzymatic browning in dried skim milk

Journal of Food Engineering, 1990

Water activity Reference water activity Constant parameters Concentration of brown pigment (OD/g)... more Water activity Reference water activity Constant parameters Concentration of brown pigment (OD/g) Solid content ("Brix) Activation energy (kcal/mol) Rate constant (OD/g d) Arrhenius frequency factor Moisture content (g &O/g dry solids) Universal gas law constant (kcal/mol K) Time (days) Absolute temperature (K)