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OHMICPROCESSING
Montica SawantSY Tech (FET)13FET1007
What is ohmic heating Ohmic heating is an advanced thermal processing method wherein the food
material which serves as an electrical resistor is heated by passing electricity through it
Unlike conventional heating where heat transfer occurs from a heated surface to the product interior by means of convection and conduction Ohmic heating has insidendashoutside heat transfer pattern
Electrical energy is dissipated into heat which results in rapid and uniform heating with minimal thermal degradation
Also called electrical resistance heating Joule heating or electro-heating and may be used for a variety of applications in the food industry
Similar to HTST processing with the added benefit of uniform and complete heating of particulate food systems like soups
PRINCIPLE Based on the passage of
alternating electrical current (AC) through a body such as a liquid-particulate food system which serves as an electrical resistance in which heat is generated
Foods contain water amp ionic salts capable of conducting electricity but also have a resistance which generates heat when an electric current is passed through This resistance produces heat
Inactivate microorganisms by heat and additional electroporatic effect
WORKING Electrode Platinized
titanium electrode to prevent leaching(ofte coated with a high temp inert plastic material) (if steel stainless steel electrodees are used working at frequencies of above 100khz eliminates this problem)
Temp 40-140 degree C for lt90 sec followed by cooling for 15 minutes
Pressure of up to 4 bar for UHT to prevent product from boiling
Frequency 50-60 Hz Voltage upto 5000 V Uniform mass flow rate
httpdisciplinasstoauspbrpluginfilephp234401mod_resourcecontent1cr1216_13pdf
A viscous food product containing particulates enters the continuous-flow ohmic heating system via a feed pump hopper
The product then flows past a series of electrodes in the ohmic column where it is heated to process temperature
Then the product enters the holding tubes for a fixed time to achieve commercial sterility
Next the product flows through tubular coolers and into storage tanks where it is stored until filling and packaging
Shelf life of Ohmically processed foods is comparable to canned and sterile aseptically processed products
CONTROL PARAMETERS Electrical conductivity temperature
dependence of conductivity design of heating device residence time thermo physical properties of food electric field strength
However the most important factor is the electrical conductivity of the product and its temperature dependence
If the product has more than one phase such as in the case of a mixture of liquid and particulates the electrical conductivity of all the phases has to be considered
The electrical conductivity increases with rising temperature(resistance of food falls by factor of 2 to 3 over temperature rise of 120 C)
Factors affecting ohmic heating Electrical conductivity of food and food mixture which in
turn depends on food components ionic components (salt) acid and moisture mobility increase electrical conductivity while fats lipids and alcohol decrease it
Fluid viscosity higher viscosity fluids shows faster ohmic heating than lower viscosity fluids
In case of liquid + solid mixture the property difference of the two components also affects ohmic heating particulate size (upto 25mm ideally )
Density and specific heat of the food product
Applications Ohmic heating can be used for heating liquid foods
containing large particulates such as soups stews and fruit slices in syrups and sauces and heat sensitive liquids
The technology is useful for the treatment of proteinaceous foods which tend to denature and coagulate when thermally processed For example liquid egg can be ohmically heated in a fraction of a second without coagulating it
Juices can be treated to inactivate enzymes without affecting the flavor
Other potential applications of ohmic heating include blanching thawing on-line detection of starch gelatinization fermentation peeling dehydration and extraction
Currently used in a large number of fruit processing plants in the US and Europe
Advantages Disadvantages
It can heat particulate foods and Liquidndashparticle mixtures (impossible by conventional methods)By ohmic heating high temperatures can be rapidly achieved(due to uniform heating) For eg temperatures for ultra high temperature (UHT) processing
As there are no hot surfaces for heat transfer there is low risk of product damage due to burning
It has high energy conversion efficiency (90)
It requires relatively low capital cost
Very clean and hygienic systems
Minimal thermal deterioration of food resulting in minimal mechanical damage and better nutrients and vitamin retention shorter operation time
Complex relationship between conductivity and temperature
Leaching of electrode material into the food systems
ohmically processed multi-phase food product Not yet approved by the FDA (as of 2001)
Expensive in terms of installation and equipment manufacture
Low conductivity foods cannot be processed eg foods having fat globules
Rapid increase of conductivity with temperature may lead to ldquorunaway heatingrdquo
Lack of data concerning critical factors affecting heating including residence time orientations loading levels etc
Lack of data correlating the differences in conductivity of different phases
What is ohmic heating Ohmic heating is an advanced thermal processing method wherein the food
material which serves as an electrical resistor is heated by passing electricity through it
Unlike conventional heating where heat transfer occurs from a heated surface to the product interior by means of convection and conduction Ohmic heating has insidendashoutside heat transfer pattern
Electrical energy is dissipated into heat which results in rapid and uniform heating with minimal thermal degradation
Also called electrical resistance heating Joule heating or electro-heating and may be used for a variety of applications in the food industry
Similar to HTST processing with the added benefit of uniform and complete heating of particulate food systems like soups
PRINCIPLE Based on the passage of
alternating electrical current (AC) through a body such as a liquid-particulate food system which serves as an electrical resistance in which heat is generated
Foods contain water amp ionic salts capable of conducting electricity but also have a resistance which generates heat when an electric current is passed through This resistance produces heat
Inactivate microorganisms by heat and additional electroporatic effect
WORKING Electrode Platinized
titanium electrode to prevent leaching(ofte coated with a high temp inert plastic material) (if steel stainless steel electrodees are used working at frequencies of above 100khz eliminates this problem)
Temp 40-140 degree C for lt90 sec followed by cooling for 15 minutes
Pressure of up to 4 bar for UHT to prevent product from boiling
Frequency 50-60 Hz Voltage upto 5000 V Uniform mass flow rate
httpdisciplinasstoauspbrpluginfilephp234401mod_resourcecontent1cr1216_13pdf
A viscous food product containing particulates enters the continuous-flow ohmic heating system via a feed pump hopper
The product then flows past a series of electrodes in the ohmic column where it is heated to process temperature
Then the product enters the holding tubes for a fixed time to achieve commercial sterility
Next the product flows through tubular coolers and into storage tanks where it is stored until filling and packaging
Shelf life of Ohmically processed foods is comparable to canned and sterile aseptically processed products
CONTROL PARAMETERS Electrical conductivity temperature
dependence of conductivity design of heating device residence time thermo physical properties of food electric field strength
However the most important factor is the electrical conductivity of the product and its temperature dependence
If the product has more than one phase such as in the case of a mixture of liquid and particulates the electrical conductivity of all the phases has to be considered
The electrical conductivity increases with rising temperature(resistance of food falls by factor of 2 to 3 over temperature rise of 120 C)
Factors affecting ohmic heating Electrical conductivity of food and food mixture which in
turn depends on food components ionic components (salt) acid and moisture mobility increase electrical conductivity while fats lipids and alcohol decrease it
Fluid viscosity higher viscosity fluids shows faster ohmic heating than lower viscosity fluids
In case of liquid + solid mixture the property difference of the two components also affects ohmic heating particulate size (upto 25mm ideally )
Density and specific heat of the food product
Applications Ohmic heating can be used for heating liquid foods
containing large particulates such as soups stews and fruit slices in syrups and sauces and heat sensitive liquids
The technology is useful for the treatment of proteinaceous foods which tend to denature and coagulate when thermally processed For example liquid egg can be ohmically heated in a fraction of a second without coagulating it
Juices can be treated to inactivate enzymes without affecting the flavor
Other potential applications of ohmic heating include blanching thawing on-line detection of starch gelatinization fermentation peeling dehydration and extraction
Currently used in a large number of fruit processing plants in the US and Europe
Advantages Disadvantages
It can heat particulate foods and Liquidndashparticle mixtures (impossible by conventional methods)By ohmic heating high temperatures can be rapidly achieved(due to uniform heating) For eg temperatures for ultra high temperature (UHT) processing
As there are no hot surfaces for heat transfer there is low risk of product damage due to burning
It has high energy conversion efficiency (90)
It requires relatively low capital cost
Very clean and hygienic systems
Minimal thermal deterioration of food resulting in minimal mechanical damage and better nutrients and vitamin retention shorter operation time
Complex relationship between conductivity and temperature
Leaching of electrode material into the food systems
ohmically processed multi-phase food product Not yet approved by the FDA (as of 2001)
Expensive in terms of installation and equipment manufacture
Low conductivity foods cannot be processed eg foods having fat globules
Rapid increase of conductivity with temperature may lead to ldquorunaway heatingrdquo
Lack of data concerning critical factors affecting heating including residence time orientations loading levels etc
Lack of data correlating the differences in conductivity of different phases
PRINCIPLE Based on the passage of
alternating electrical current (AC) through a body such as a liquid-particulate food system which serves as an electrical resistance in which heat is generated
Foods contain water amp ionic salts capable of conducting electricity but also have a resistance which generates heat when an electric current is passed through This resistance produces heat
Inactivate microorganisms by heat and additional electroporatic effect
WORKING Electrode Platinized
titanium electrode to prevent leaching(ofte coated with a high temp inert plastic material) (if steel stainless steel electrodees are used working at frequencies of above 100khz eliminates this problem)
Temp 40-140 degree C for lt90 sec followed by cooling for 15 minutes
Pressure of up to 4 bar for UHT to prevent product from boiling
Frequency 50-60 Hz Voltage upto 5000 V Uniform mass flow rate
httpdisciplinasstoauspbrpluginfilephp234401mod_resourcecontent1cr1216_13pdf
A viscous food product containing particulates enters the continuous-flow ohmic heating system via a feed pump hopper
The product then flows past a series of electrodes in the ohmic column where it is heated to process temperature
Then the product enters the holding tubes for a fixed time to achieve commercial sterility
Next the product flows through tubular coolers and into storage tanks where it is stored until filling and packaging
Shelf life of Ohmically processed foods is comparable to canned and sterile aseptically processed products
CONTROL PARAMETERS Electrical conductivity temperature
dependence of conductivity design of heating device residence time thermo physical properties of food electric field strength
However the most important factor is the electrical conductivity of the product and its temperature dependence
If the product has more than one phase such as in the case of a mixture of liquid and particulates the electrical conductivity of all the phases has to be considered
The electrical conductivity increases with rising temperature(resistance of food falls by factor of 2 to 3 over temperature rise of 120 C)
Factors affecting ohmic heating Electrical conductivity of food and food mixture which in
turn depends on food components ionic components (salt) acid and moisture mobility increase electrical conductivity while fats lipids and alcohol decrease it
Fluid viscosity higher viscosity fluids shows faster ohmic heating than lower viscosity fluids
In case of liquid + solid mixture the property difference of the two components also affects ohmic heating particulate size (upto 25mm ideally )
Density and specific heat of the food product
Applications Ohmic heating can be used for heating liquid foods
containing large particulates such as soups stews and fruit slices in syrups and sauces and heat sensitive liquids
The technology is useful for the treatment of proteinaceous foods which tend to denature and coagulate when thermally processed For example liquid egg can be ohmically heated in a fraction of a second without coagulating it
Juices can be treated to inactivate enzymes without affecting the flavor
Other potential applications of ohmic heating include blanching thawing on-line detection of starch gelatinization fermentation peeling dehydration and extraction
Currently used in a large number of fruit processing plants in the US and Europe
Advantages Disadvantages
It can heat particulate foods and Liquidndashparticle mixtures (impossible by conventional methods)By ohmic heating high temperatures can be rapidly achieved(due to uniform heating) For eg temperatures for ultra high temperature (UHT) processing
As there are no hot surfaces for heat transfer there is low risk of product damage due to burning
It has high energy conversion efficiency (90)
It requires relatively low capital cost
Very clean and hygienic systems
Minimal thermal deterioration of food resulting in minimal mechanical damage and better nutrients and vitamin retention shorter operation time
Complex relationship between conductivity and temperature
Leaching of electrode material into the food systems
ohmically processed multi-phase food product Not yet approved by the FDA (as of 2001)
Expensive in terms of installation and equipment manufacture
Low conductivity foods cannot be processed eg foods having fat globules
Rapid increase of conductivity with temperature may lead to ldquorunaway heatingrdquo
Lack of data concerning critical factors affecting heating including residence time orientations loading levels etc
Lack of data correlating the differences in conductivity of different phases
WORKING Electrode Platinized
titanium electrode to prevent leaching(ofte coated with a high temp inert plastic material) (if steel stainless steel electrodees are used working at frequencies of above 100khz eliminates this problem)
Temp 40-140 degree C for lt90 sec followed by cooling for 15 minutes
Pressure of up to 4 bar for UHT to prevent product from boiling
Frequency 50-60 Hz Voltage upto 5000 V Uniform mass flow rate
httpdisciplinasstoauspbrpluginfilephp234401mod_resourcecontent1cr1216_13pdf
A viscous food product containing particulates enters the continuous-flow ohmic heating system via a feed pump hopper
The product then flows past a series of electrodes in the ohmic column where it is heated to process temperature
Then the product enters the holding tubes for a fixed time to achieve commercial sterility
Next the product flows through tubular coolers and into storage tanks where it is stored until filling and packaging
Shelf life of Ohmically processed foods is comparable to canned and sterile aseptically processed products
CONTROL PARAMETERS Electrical conductivity temperature
dependence of conductivity design of heating device residence time thermo physical properties of food electric field strength
However the most important factor is the electrical conductivity of the product and its temperature dependence
If the product has more than one phase such as in the case of a mixture of liquid and particulates the electrical conductivity of all the phases has to be considered
The electrical conductivity increases with rising temperature(resistance of food falls by factor of 2 to 3 over temperature rise of 120 C)
Factors affecting ohmic heating Electrical conductivity of food and food mixture which in
turn depends on food components ionic components (salt) acid and moisture mobility increase electrical conductivity while fats lipids and alcohol decrease it
Fluid viscosity higher viscosity fluids shows faster ohmic heating than lower viscosity fluids
In case of liquid + solid mixture the property difference of the two components also affects ohmic heating particulate size (upto 25mm ideally )
Density and specific heat of the food product
Applications Ohmic heating can be used for heating liquid foods
containing large particulates such as soups stews and fruit slices in syrups and sauces and heat sensitive liquids
The technology is useful for the treatment of proteinaceous foods which tend to denature and coagulate when thermally processed For example liquid egg can be ohmically heated in a fraction of a second without coagulating it
Juices can be treated to inactivate enzymes without affecting the flavor
Other potential applications of ohmic heating include blanching thawing on-line detection of starch gelatinization fermentation peeling dehydration and extraction
Currently used in a large number of fruit processing plants in the US and Europe
Advantages Disadvantages
It can heat particulate foods and Liquidndashparticle mixtures (impossible by conventional methods)By ohmic heating high temperatures can be rapidly achieved(due to uniform heating) For eg temperatures for ultra high temperature (UHT) processing
As there are no hot surfaces for heat transfer there is low risk of product damage due to burning
It has high energy conversion efficiency (90)
It requires relatively low capital cost
Very clean and hygienic systems
Minimal thermal deterioration of food resulting in minimal mechanical damage and better nutrients and vitamin retention shorter operation time
Complex relationship between conductivity and temperature
Leaching of electrode material into the food systems
ohmically processed multi-phase food product Not yet approved by the FDA (as of 2001)
Expensive in terms of installation and equipment manufacture
Low conductivity foods cannot be processed eg foods having fat globules
Rapid increase of conductivity with temperature may lead to ldquorunaway heatingrdquo
Lack of data concerning critical factors affecting heating including residence time orientations loading levels etc
Lack of data correlating the differences in conductivity of different phases
A viscous food product containing particulates enters the continuous-flow ohmic heating system via a feed pump hopper
The product then flows past a series of electrodes in the ohmic column where it is heated to process temperature
Then the product enters the holding tubes for a fixed time to achieve commercial sterility
Next the product flows through tubular coolers and into storage tanks where it is stored until filling and packaging
Shelf life of Ohmically processed foods is comparable to canned and sterile aseptically processed products
CONTROL PARAMETERS Electrical conductivity temperature
dependence of conductivity design of heating device residence time thermo physical properties of food electric field strength
However the most important factor is the electrical conductivity of the product and its temperature dependence
If the product has more than one phase such as in the case of a mixture of liquid and particulates the electrical conductivity of all the phases has to be considered
The electrical conductivity increases with rising temperature(resistance of food falls by factor of 2 to 3 over temperature rise of 120 C)
Factors affecting ohmic heating Electrical conductivity of food and food mixture which in
turn depends on food components ionic components (salt) acid and moisture mobility increase electrical conductivity while fats lipids and alcohol decrease it
Fluid viscosity higher viscosity fluids shows faster ohmic heating than lower viscosity fluids
In case of liquid + solid mixture the property difference of the two components also affects ohmic heating particulate size (upto 25mm ideally )
Density and specific heat of the food product
Applications Ohmic heating can be used for heating liquid foods
containing large particulates such as soups stews and fruit slices in syrups and sauces and heat sensitive liquids
The technology is useful for the treatment of proteinaceous foods which tend to denature and coagulate when thermally processed For example liquid egg can be ohmically heated in a fraction of a second without coagulating it
Juices can be treated to inactivate enzymes without affecting the flavor
Other potential applications of ohmic heating include blanching thawing on-line detection of starch gelatinization fermentation peeling dehydration and extraction
Currently used in a large number of fruit processing plants in the US and Europe
Advantages Disadvantages
It can heat particulate foods and Liquidndashparticle mixtures (impossible by conventional methods)By ohmic heating high temperatures can be rapidly achieved(due to uniform heating) For eg temperatures for ultra high temperature (UHT) processing
As there are no hot surfaces for heat transfer there is low risk of product damage due to burning
It has high energy conversion efficiency (90)
It requires relatively low capital cost
Very clean and hygienic systems
Minimal thermal deterioration of food resulting in minimal mechanical damage and better nutrients and vitamin retention shorter operation time
Complex relationship between conductivity and temperature
Leaching of electrode material into the food systems
ohmically processed multi-phase food product Not yet approved by the FDA (as of 2001)
Expensive in terms of installation and equipment manufacture
Low conductivity foods cannot be processed eg foods having fat globules
Rapid increase of conductivity with temperature may lead to ldquorunaway heatingrdquo
Lack of data concerning critical factors affecting heating including residence time orientations loading levels etc
Lack of data correlating the differences in conductivity of different phases
CONTROL PARAMETERS Electrical conductivity temperature
dependence of conductivity design of heating device residence time thermo physical properties of food electric field strength
However the most important factor is the electrical conductivity of the product and its temperature dependence
If the product has more than one phase such as in the case of a mixture of liquid and particulates the electrical conductivity of all the phases has to be considered
The electrical conductivity increases with rising temperature(resistance of food falls by factor of 2 to 3 over temperature rise of 120 C)
Factors affecting ohmic heating Electrical conductivity of food and food mixture which in
turn depends on food components ionic components (salt) acid and moisture mobility increase electrical conductivity while fats lipids and alcohol decrease it
Fluid viscosity higher viscosity fluids shows faster ohmic heating than lower viscosity fluids
In case of liquid + solid mixture the property difference of the two components also affects ohmic heating particulate size (upto 25mm ideally )
Density and specific heat of the food product
Applications Ohmic heating can be used for heating liquid foods
containing large particulates such as soups stews and fruit slices in syrups and sauces and heat sensitive liquids
The technology is useful for the treatment of proteinaceous foods which tend to denature and coagulate when thermally processed For example liquid egg can be ohmically heated in a fraction of a second without coagulating it
Juices can be treated to inactivate enzymes without affecting the flavor
Other potential applications of ohmic heating include blanching thawing on-line detection of starch gelatinization fermentation peeling dehydration and extraction
Currently used in a large number of fruit processing plants in the US and Europe
Advantages Disadvantages
It can heat particulate foods and Liquidndashparticle mixtures (impossible by conventional methods)By ohmic heating high temperatures can be rapidly achieved(due to uniform heating) For eg temperatures for ultra high temperature (UHT) processing
As there are no hot surfaces for heat transfer there is low risk of product damage due to burning
It has high energy conversion efficiency (90)
It requires relatively low capital cost
Very clean and hygienic systems
Minimal thermal deterioration of food resulting in minimal mechanical damage and better nutrients and vitamin retention shorter operation time
Complex relationship between conductivity and temperature
Leaching of electrode material into the food systems
ohmically processed multi-phase food product Not yet approved by the FDA (as of 2001)
Expensive in terms of installation and equipment manufacture
Low conductivity foods cannot be processed eg foods having fat globules
Rapid increase of conductivity with temperature may lead to ldquorunaway heatingrdquo
Lack of data concerning critical factors affecting heating including residence time orientations loading levels etc
Lack of data correlating the differences in conductivity of different phases
Factors affecting ohmic heating Electrical conductivity of food and food mixture which in
turn depends on food components ionic components (salt) acid and moisture mobility increase electrical conductivity while fats lipids and alcohol decrease it
Fluid viscosity higher viscosity fluids shows faster ohmic heating than lower viscosity fluids
In case of liquid + solid mixture the property difference of the two components also affects ohmic heating particulate size (upto 25mm ideally )
Density and specific heat of the food product
Applications Ohmic heating can be used for heating liquid foods
containing large particulates such as soups stews and fruit slices in syrups and sauces and heat sensitive liquids
The technology is useful for the treatment of proteinaceous foods which tend to denature and coagulate when thermally processed For example liquid egg can be ohmically heated in a fraction of a second without coagulating it
Juices can be treated to inactivate enzymes without affecting the flavor
Other potential applications of ohmic heating include blanching thawing on-line detection of starch gelatinization fermentation peeling dehydration and extraction
Currently used in a large number of fruit processing plants in the US and Europe
Advantages Disadvantages
It can heat particulate foods and Liquidndashparticle mixtures (impossible by conventional methods)By ohmic heating high temperatures can be rapidly achieved(due to uniform heating) For eg temperatures for ultra high temperature (UHT) processing
As there are no hot surfaces for heat transfer there is low risk of product damage due to burning
It has high energy conversion efficiency (90)
It requires relatively low capital cost
Very clean and hygienic systems
Minimal thermal deterioration of food resulting in minimal mechanical damage and better nutrients and vitamin retention shorter operation time
Complex relationship between conductivity and temperature
Leaching of electrode material into the food systems
ohmically processed multi-phase food product Not yet approved by the FDA (as of 2001)
Expensive in terms of installation and equipment manufacture
Low conductivity foods cannot be processed eg foods having fat globules
Rapid increase of conductivity with temperature may lead to ldquorunaway heatingrdquo
Lack of data concerning critical factors affecting heating including residence time orientations loading levels etc
Lack of data correlating the differences in conductivity of different phases
Applications Ohmic heating can be used for heating liquid foods
containing large particulates such as soups stews and fruit slices in syrups and sauces and heat sensitive liquids
The technology is useful for the treatment of proteinaceous foods which tend to denature and coagulate when thermally processed For example liquid egg can be ohmically heated in a fraction of a second without coagulating it
Juices can be treated to inactivate enzymes without affecting the flavor
Other potential applications of ohmic heating include blanching thawing on-line detection of starch gelatinization fermentation peeling dehydration and extraction
Currently used in a large number of fruit processing plants in the US and Europe
Advantages Disadvantages
It can heat particulate foods and Liquidndashparticle mixtures (impossible by conventional methods)By ohmic heating high temperatures can be rapidly achieved(due to uniform heating) For eg temperatures for ultra high temperature (UHT) processing
As there are no hot surfaces for heat transfer there is low risk of product damage due to burning
It has high energy conversion efficiency (90)
It requires relatively low capital cost
Very clean and hygienic systems
Minimal thermal deterioration of food resulting in minimal mechanical damage and better nutrients and vitamin retention shorter operation time
Complex relationship between conductivity and temperature
Leaching of electrode material into the food systems
ohmically processed multi-phase food product Not yet approved by the FDA (as of 2001)
Expensive in terms of installation and equipment manufacture
Low conductivity foods cannot be processed eg foods having fat globules
Rapid increase of conductivity with temperature may lead to ldquorunaway heatingrdquo
Lack of data concerning critical factors affecting heating including residence time orientations loading levels etc
Lack of data correlating the differences in conductivity of different phases
Advantages Disadvantages
It can heat particulate foods and Liquidndashparticle mixtures (impossible by conventional methods)By ohmic heating high temperatures can be rapidly achieved(due to uniform heating) For eg temperatures for ultra high temperature (UHT) processing
As there are no hot surfaces for heat transfer there is low risk of product damage due to burning
It has high energy conversion efficiency (90)
It requires relatively low capital cost
Very clean and hygienic systems
Minimal thermal deterioration of food resulting in minimal mechanical damage and better nutrients and vitamin retention shorter operation time
Complex relationship between conductivity and temperature
Leaching of electrode material into the food systems
ohmically processed multi-phase food product Not yet approved by the FDA (as of 2001)
Expensive in terms of installation and equipment manufacture
Low conductivity foods cannot be processed eg foods having fat globules
Rapid increase of conductivity with temperature may lead to ldquorunaway heatingrdquo
Lack of data concerning critical factors affecting heating including residence time orientations loading levels etc
Lack of data correlating the differences in conductivity of different phases
