Microwaves are electromagnetic waves with wavelengths between 1 mm and 1 m that are used for heating. Microwave ovens generate microwaves at a frequency of 2.45 GHz to heat food through rotation and ionic conduction, causing more efficient heating than conventional methods. The key components of a microwave oven are the magnetron which generates microwaves, the waveguide which directs the waves, and the cooking cavity where food is placed. Microwaves are also used for industrial applications like pasteurization, sterilization, drying and heating materials.
1) The document presents a case study on tomato peeling using ohmic heating with lye-salt combinations. Experiments were conducted to determine the effects of electric field strength and salt-lye composition on peeling time and the diffusion of sodium hydroxide through the tomato peel.
2) Results showed that treatments with 0.01/0.5% NaCl/NaOH at 1610 V/m and 0.01/1.0% NaCl/NaOH at 1450 V/m had the shortest peeling times. Diffusivities for lye peeling with ohmic heating were greater than without at both 50 and 65°C.
3) It was concluded that the electric field enhances
Ohmic heating is an advanced thermal processing method that uses direct resistance heating to heat food products. It works by passing an electric current through the food, with the food itself serving as the resistor to generate heat. Ohmic heating allows for rapid and uniform heating throughout the product at rates of 1-100°C/s. It has advantages over conventional heating like reduced nutrient loss, uniform heating, and faster processing times. Some potential applications of ohmic heating in food processing include meat processing, milk pasteurization, fruit and vegetable blanching, and waste water treatment. However, further research is still needed to fully understand and control the process and address issues like preventing electrolysis during heating.
This document discusses pulsed electric field (PEF) processing as a non-thermal food preservation technique. PEF uses short, high-voltage electric pulses to induce pores in microbial cell membranes, leading to cell disintegration and microbial inactivation while minimizing negative impacts on sensory and nutritional properties. The document outlines various PEF applications, factors that influence microbial inactivation, commercially available PEF systems, ongoing research needs, and the potential future of PEF processing.
1. The document discusses three methods for producing ozone: corona discharge, ultraviolet radiation, and electrolysis. It then focuses on using ozone as a disinfectant in food applications such as bottled water, fruits and vegetables, and cold food storage.
2. Two studies are summarized that examine the effects of ozone treatment on postharvest carrots and dates. The first study looks at ozone as gas and dissolved in water on carrot quality factors like weight loss and firmness. The second analyzes using ozone gas to reduce microbial populations on dates.
3. Both studies found that ozone treatment was generally effective at reducing microbes without negatively impacting quality factors in the treated foods. O
Non thermal processing of food- Pulsed electric field and visible lightT. Tamilselvan
This document provides information on pulsed electric field (PEF) and pulsed visible light processing of foods. PEF uses short electric pulses to preserve foods through electroporation of microbial cell membranes, while minimizing heat production. PEF has been shown to effectively inactivate various microbes in foods like milk, eggs and juices. Pulsed visible light also uses intense, brief pulses of light to inactivate microbes in foods photochemically and through localized heating. Both techniques are non-thermal alternatives to traditional food processing that reduce degradation of nutritional and sensory qualities compared to heat treatments.
This document discusses pulsed electric field (PEF) technology. PEF uses short electric pulses to preserve foods without heat, maintaining fresh qualities and nutrients. It can extend shelf life while ensuring safety. PEF works by applying high-intensity pulses that cause microbial cell membranes to break down without significantly heating the food. PEF has various applications, including pasteurizing juices and milk. It provides advantages like minimal processing, color/flavor retention, and higher nutritional value compared to thermal treatments.
Non thermal process in preservation of foodGazanfar Abass
The document discusses various non-thermal food processing techniques as alternatives to traditional thermal processing. It provides examples of different non-thermal methods like pulsed electric field, high pressure processing, pulsed light technology, microwave heating, ohmic heating, and irradiation. These methods aim to increase production rates and profits for food industries while maintaining better quality, nutrients, flavor and extending shelf life compared to thermal processing which can result in loss of volatile compounds. The non-thermal methods are particularly suitable for large scale and liquid food production.
Microwaves are electromagnetic waves with wavelengths between 1 mm and 1 m that are used for heating. Microwave ovens generate microwaves at a frequency of 2.45 GHz to heat food through rotation and ionic conduction, causing more efficient heating than conventional methods. The key components of a microwave oven are the magnetron which generates microwaves, the waveguide which directs the waves, and the cooking cavity where food is placed. Microwaves are also used for industrial applications like pasteurization, sterilization, drying and heating materials.
1) The document presents a case study on tomato peeling using ohmic heating with lye-salt combinations. Experiments were conducted to determine the effects of electric field strength and salt-lye composition on peeling time and the diffusion of sodium hydroxide through the tomato peel.
2) Results showed that treatments with 0.01/0.5% NaCl/NaOH at 1610 V/m and 0.01/1.0% NaCl/NaOH at 1450 V/m had the shortest peeling times. Diffusivities for lye peeling with ohmic heating were greater than without at both 50 and 65°C.
3) It was concluded that the electric field enhances
Ohmic heating is an advanced thermal processing method that uses direct resistance heating to heat food products. It works by passing an electric current through the food, with the food itself serving as the resistor to generate heat. Ohmic heating allows for rapid and uniform heating throughout the product at rates of 1-100°C/s. It has advantages over conventional heating like reduced nutrient loss, uniform heating, and faster processing times. Some potential applications of ohmic heating in food processing include meat processing, milk pasteurization, fruit and vegetable blanching, and waste water treatment. However, further research is still needed to fully understand and control the process and address issues like preventing electrolysis during heating.
This document discusses pulsed electric field (PEF) processing as a non-thermal food preservation technique. PEF uses short, high-voltage electric pulses to induce pores in microbial cell membranes, leading to cell disintegration and microbial inactivation while minimizing negative impacts on sensory and nutritional properties. The document outlines various PEF applications, factors that influence microbial inactivation, commercially available PEF systems, ongoing research needs, and the potential future of PEF processing.
1. The document discusses three methods for producing ozone: corona discharge, ultraviolet radiation, and electrolysis. It then focuses on using ozone as a disinfectant in food applications such as bottled water, fruits and vegetables, and cold food storage.
2. Two studies are summarized that examine the effects of ozone treatment on postharvest carrots and dates. The first study looks at ozone as gas and dissolved in water on carrot quality factors like weight loss and firmness. The second analyzes using ozone gas to reduce microbial populations on dates.
3. Both studies found that ozone treatment was generally effective at reducing microbes without negatively impacting quality factors in the treated foods. O
Non thermal processing of food- Pulsed electric field and visible lightT. Tamilselvan
This document provides information on pulsed electric field (PEF) and pulsed visible light processing of foods. PEF uses short electric pulses to preserve foods through electroporation of microbial cell membranes, while minimizing heat production. PEF has been shown to effectively inactivate various microbes in foods like milk, eggs and juices. Pulsed visible light also uses intense, brief pulses of light to inactivate microbes in foods photochemically and through localized heating. Both techniques are non-thermal alternatives to traditional food processing that reduce degradation of nutritional and sensory qualities compared to heat treatments.
This document discusses pulsed electric field (PEF) technology. PEF uses short electric pulses to preserve foods without heat, maintaining fresh qualities and nutrients. It can extend shelf life while ensuring safety. PEF works by applying high-intensity pulses that cause microbial cell membranes to break down without significantly heating the food. PEF has various applications, including pasteurizing juices and milk. It provides advantages like minimal processing, color/flavor retention, and higher nutritional value compared to thermal treatments.
Non thermal process in preservation of foodGazanfar Abass
The document discusses various non-thermal food processing techniques as alternatives to traditional thermal processing. It provides examples of different non-thermal methods like pulsed electric field, high pressure processing, pulsed light technology, microwave heating, ohmic heating, and irradiation. These methods aim to increase production rates and profits for food industries while maintaining better quality, nutrients, flavor and extending shelf life compared to thermal processing which can result in loss of volatile compounds. The non-thermal methods are particularly suitable for large scale and liquid food production.
This document discusses freeze drying (lyophilization), including its principles, stages of the process, methods of freezing materials, advantages, and applications. Freeze drying works by first freezing the material to be preserved and then removing water by sublimation under a vacuum. This preserves the material's structure and composition while removing moisture. Common applications of freeze drying include preserving pharmaceuticals, foods, and biological materials as it results in materials that can be stored at room temperature for extended periods of time.
Baking and roasting are similar processes that use heated air to alter the quality of foods. Baking is typically used for flour-based foods and fruits, while roasting is for meats, nuts and vegetables. Both processes involve heat transfer through radiation, convection and conduction to cook foods internally without exceeding 100°C. This causes surface changes that improve qualities like moisture retention. Ovens can be direct or indirect heating types, and batch, continuous or semi-continuous systems. Frying methods include deep frying by full submersion in hot oil, shallow frying with partial submersion, and stir frying using minimal oil. Frying oils undergo hydrolysis and oxidation over time, producing compounds that degrade quality
Pulsed electric field (PEF) technology uses short pulses of high-intensity electric fields to preserve foods. It offers advantages over thermal pasteurization like shorter treatment times, lower temperatures, and better retention of sensory and nutritional properties. PEF works by creating pores in microbial cell membranes, killing bacteria and extending shelf life. It has been used successfully to pasteurize various liquids like juices, milk, and soups without chemical preservatives. PEF processing also has applications in improving mass transfer for oil extraction, meat curing, sugar processing and extraction of compounds from algae and plant cells. However, high capital costs and inability to process solid foods limit its commercial use.
Thermal processing involves applying heat to food to eliminate microorganisms and enzymes. There are three main categories: blanching, which uses mild heat to inactivate enzymes; pasteurization, which uses mild heat to reduce pathogens; and sterilization, which uses more severe heat like canning to eliminate all microbes. The time and temperature combination needed depends on the processing method and the heat resistance of the target organisms. Continuous improvements aim to deliver heat more efficiently to achieve the same results with shorter processing times.
The document discusses the use of oscillating magnetic fields (OMF) to inactivate microorganisms for food preservation. OMF involves applying magnetic fields of intensities between 5-50 tesla and frequencies of 5-500 kHz. This process reduces microbial populations by at least 2 log cycles. The mechanisms of OMF inactivation involve loosening ion bonds in cell membranes and disrupting calcium/magnesium ions. While OMF shows potential for food preservation, further research is still needed to fully understand its effects on microbial destruction kinetics and food quality.
This document discusses the principles and processes of drying food products. It explains that drying involves reducing the moisture content of food to inhibit microbial growth and chemical reactions. The drying process is governed by heat and mass transfer principles. There are three main types of drying: contact/convective drying where food directly contacts drying air, vacuum drying using indirect heat, and freeze drying using sublimation. The drying rate depends on moisture content and occurs in three periods: constant rate period where the surface moisture evaporates at the same rate as interior moisture migrates outward, and two falling rate periods where the drying rate decreases as moisture diffusion slows. Selection of the appropriate dryer depends on factors like the food properties, scale of production, and
Radio frequency heating is an emerging technology for food processing that uses electromagnetic energy between 1-300 MHz to induce volumetric heating. It has advantages over conventional and microwave heating such as faster and more uniform heating. The seminar discussed the principles, mechanisms, factors affecting, and applications of RF heating in food industries like thawing, pasteurization, drying, and baking. Research shows RF heating effectively inactivates pathogens in fruit juices, milk, meat and spices without negatively impacting quality.
Hurdle technology for food preservationDeepak Verma
This document discusses hurdle technology, which uses a combination of preservation methods at optimal levels to inhibit microorganisms without compromising food quality. It explains that hurdle technology combines physical hurdles like heat treatment, freezing or modified atmosphere with physic-chemical hurdles like low pH, salt or preservatives. Some examples given are pickles which use acid and salt, and sausages which employ smoke, salt and preservatives. The advantages of hurdle technology are maintaining food safety, quality and nutrition while allowing for minimally processed foods.
Freezing curve, freezing system & freezing timeMuneeb Vml
The document discusses freezing as an operation to preserve food by lowering its temperature below the freezing point. It describes the freezing process and freezing curve, including nucleation, crystal growth, and how solute concentration changes. It discusses factors that influence freezing time like thermal conductivity and size/shape of food pieces. Methods to calculate freezing time are presented, including Planck's equation and Pham's method. Different freezing systems are outlined like air blast freezers, plate freezers, and fluidized bed freezers.
This Application Note describes the technology and applications of infrared heating. The basic principles behind the technology and its important characteristics, such as the effect of emissivity and shape coefficient on the rate of transfer of thermal energy, are described.
Infrared heating is characterized by high energy densities, rapid heating, and relative ease of installation. All these advantages offer the possibility of higher production speeds, more compact installations, and lower investment costs. Thus, in many industrial production processes, infrared heating offers advantages with respect to conventional heating techniques such as convection or hot air ovens.
Blanching is a heat treatment of fruits and vegetables that inactivates enzymes and microorganisms. It involves rapidly heating produce to a specified temperature for a short time period, then rapidly cooling it. This helps prevent quality degradation during further processing like freezing, canning, or drying by stopping enzymatic and microbial activity. Blanching also softens tissues, removes gases, and helps with peeling or packaging of produce. However, it can result in some nutrient and texture loss depending on the time-temperature combination used.
Dielectric, ohmic, infrared_heating for food productsramavatarmeena
Dielectric, ohmic, and infrared heating are forms of electromagnetic energy used to heat foods. Dielectric and ohmic heating directly generate heat within the food, while infrared heating relies on external heat application. Ohmic heating passes electric current through food, using its electrical resistance to directly convert electricity to heat throughout. Dielectric heating induces molecular friction in water to generate uniform heat. Infrared heating absorbs energy at the surface. These methods can rapidly thaw, dry, bake, and pasteurize foods with precise temperature control and minimal damage.
A non thermal processing, which primarily used for homogenisation of fat particles in liquid foods. Now emerged as a promising techniques having applications in food processing. This document will deliver the basics and applications of ultrasound in food
W.A. Mihiravi Pamuditha gave a presentation on radio frequency (RF) heating technology for food processing. RF heating uses electromagnetic energy to induce volumetric heating within foods. It has advantages over conventional heating like faster and more uniform heating. Some applications of RF heating in food include thawing, baking, drying, pasteurization and using RFID tags for tracking. While it has benefits, high equipment costs are a disadvantage. The future of RF technology may include its expanded use in continuous food processing and integration with technologies like nanotechnology and smart refrigerators.
This document discusses various methods of food concentration, including solar concentration, open kettles, flash evaporators, thin film evaporators, vacuum evaporators, freeze concentration, and ultra filtration and reverse osmosis. It also lists some commonly concentrated foods such as evaporated and sweetened condensed milks, fruit and vegetable juices, nectars, sugar syrups, flavored syrups, jams, jellies, and tomato paste. Additionally, it briefly introduces preservation by dehydration and mentions fruit juice powder.
Active packaging incorporates additives into packaging films or containers to maintain and extend the shelf life of food products. It includes oxygen scavengers, carbon dioxide generators, ethylene scavengers, and antimicrobial agents. Oxygen scavengers prevent food spoilage by chemically removing oxygen from packages through reactions with iron, ascorbic acid, or unsaturated fatty acids. Carbon dioxide generators and ethylene scavengers inhibit microbial growth and ripening to preserve freshness. Antimicrobial packaging prevents microbial growth through the release of compounds like ethanol or silver ions. Active packaging technologies are expected to grow significantly due to consumer demand for premium, safe, and convenient packaged foods.
This document discusses microwave technology in food applications. It begins by describing the properties of microwaves, including their wavelength and frequency approved for food. It then explains how microwaves are absorbed by polar molecules in food, causing heating through molecular friction. Microwave heating is described as uniform throughout the food, unlike conventional heating which occurs from the surface in. Several food applications of microwaves are listed, including baking, cooking, drying, and enzyme inactivation. The document concludes by noting the magnetron is commonly used to generate microwaves in microwave ovens and tunnel ovens.
Novel thermal technologies in food processingRahul1154
The document discusses novel thermal technologies for food processing, including microwave heating, infrared heating, and ohmic heating.
Microwave heating works by exciting water molecules in food, causing friction and generating heat. It is commonly used for drying, thawing, pasteurization, baking, and other applications. Infrared heating works by food absorbing infrared energy and converting it to heat, with the rate depending on surface properties. It is used for drying and processing. Ohmic heating passes electric current directly through food, generating heat from electrical resistance. It allows uniform, rapid heating and is used for pasteurization and other continuous processing.
This document discusses freeze drying (lyophilization), including its principles, stages of the process, methods of freezing materials, advantages, and applications. Freeze drying works by first freezing the material to be preserved and then removing water by sublimation under a vacuum. This preserves the material's structure and composition while removing moisture. Common applications of freeze drying include preserving pharmaceuticals, foods, and biological materials as it results in materials that can be stored at room temperature for extended periods of time.
Baking and roasting are similar processes that use heated air to alter the quality of foods. Baking is typically used for flour-based foods and fruits, while roasting is for meats, nuts and vegetables. Both processes involve heat transfer through radiation, convection and conduction to cook foods internally without exceeding 100°C. This causes surface changes that improve qualities like moisture retention. Ovens can be direct or indirect heating types, and batch, continuous or semi-continuous systems. Frying methods include deep frying by full submersion in hot oil, shallow frying with partial submersion, and stir frying using minimal oil. Frying oils undergo hydrolysis and oxidation over time, producing compounds that degrade quality
Pulsed electric field (PEF) technology uses short pulses of high-intensity electric fields to preserve foods. It offers advantages over thermal pasteurization like shorter treatment times, lower temperatures, and better retention of sensory and nutritional properties. PEF works by creating pores in microbial cell membranes, killing bacteria and extending shelf life. It has been used successfully to pasteurize various liquids like juices, milk, and soups without chemical preservatives. PEF processing also has applications in improving mass transfer for oil extraction, meat curing, sugar processing and extraction of compounds from algae and plant cells. However, high capital costs and inability to process solid foods limit its commercial use.
Thermal processing involves applying heat to food to eliminate microorganisms and enzymes. There are three main categories: blanching, which uses mild heat to inactivate enzymes; pasteurization, which uses mild heat to reduce pathogens; and sterilization, which uses more severe heat like canning to eliminate all microbes. The time and temperature combination needed depends on the processing method and the heat resistance of the target organisms. Continuous improvements aim to deliver heat more efficiently to achieve the same results with shorter processing times.
The document discusses the use of oscillating magnetic fields (OMF) to inactivate microorganisms for food preservation. OMF involves applying magnetic fields of intensities between 5-50 tesla and frequencies of 5-500 kHz. This process reduces microbial populations by at least 2 log cycles. The mechanisms of OMF inactivation involve loosening ion bonds in cell membranes and disrupting calcium/magnesium ions. While OMF shows potential for food preservation, further research is still needed to fully understand its effects on microbial destruction kinetics and food quality.
This document discusses the principles and processes of drying food products. It explains that drying involves reducing the moisture content of food to inhibit microbial growth and chemical reactions. The drying process is governed by heat and mass transfer principles. There are three main types of drying: contact/convective drying where food directly contacts drying air, vacuum drying using indirect heat, and freeze drying using sublimation. The drying rate depends on moisture content and occurs in three periods: constant rate period where the surface moisture evaporates at the same rate as interior moisture migrates outward, and two falling rate periods where the drying rate decreases as moisture diffusion slows. Selection of the appropriate dryer depends on factors like the food properties, scale of production, and
Radio frequency heating is an emerging technology for food processing that uses electromagnetic energy between 1-300 MHz to induce volumetric heating. It has advantages over conventional and microwave heating such as faster and more uniform heating. The seminar discussed the principles, mechanisms, factors affecting, and applications of RF heating in food industries like thawing, pasteurization, drying, and baking. Research shows RF heating effectively inactivates pathogens in fruit juices, milk, meat and spices without negatively impacting quality.
Hurdle technology for food preservationDeepak Verma
This document discusses hurdle technology, which uses a combination of preservation methods at optimal levels to inhibit microorganisms without compromising food quality. It explains that hurdle technology combines physical hurdles like heat treatment, freezing or modified atmosphere with physic-chemical hurdles like low pH, salt or preservatives. Some examples given are pickles which use acid and salt, and sausages which employ smoke, salt and preservatives. The advantages of hurdle technology are maintaining food safety, quality and nutrition while allowing for minimally processed foods.
Freezing curve, freezing system & freezing timeMuneeb Vml
The document discusses freezing as an operation to preserve food by lowering its temperature below the freezing point. It describes the freezing process and freezing curve, including nucleation, crystal growth, and how solute concentration changes. It discusses factors that influence freezing time like thermal conductivity and size/shape of food pieces. Methods to calculate freezing time are presented, including Planck's equation and Pham's method. Different freezing systems are outlined like air blast freezers, plate freezers, and fluidized bed freezers.
This Application Note describes the technology and applications of infrared heating. The basic principles behind the technology and its important characteristics, such as the effect of emissivity and shape coefficient on the rate of transfer of thermal energy, are described.
Infrared heating is characterized by high energy densities, rapid heating, and relative ease of installation. All these advantages offer the possibility of higher production speeds, more compact installations, and lower investment costs. Thus, in many industrial production processes, infrared heating offers advantages with respect to conventional heating techniques such as convection or hot air ovens.
Blanching is a heat treatment of fruits and vegetables that inactivates enzymes and microorganisms. It involves rapidly heating produce to a specified temperature for a short time period, then rapidly cooling it. This helps prevent quality degradation during further processing like freezing, canning, or drying by stopping enzymatic and microbial activity. Blanching also softens tissues, removes gases, and helps with peeling or packaging of produce. However, it can result in some nutrient and texture loss depending on the time-temperature combination used.
Dielectric, ohmic, infrared_heating for food productsramavatarmeena
Dielectric, ohmic, and infrared heating are forms of electromagnetic energy used to heat foods. Dielectric and ohmic heating directly generate heat within the food, while infrared heating relies on external heat application. Ohmic heating passes electric current through food, using its electrical resistance to directly convert electricity to heat throughout. Dielectric heating induces molecular friction in water to generate uniform heat. Infrared heating absorbs energy at the surface. These methods can rapidly thaw, dry, bake, and pasteurize foods with precise temperature control and minimal damage.
A non thermal processing, which primarily used for homogenisation of fat particles in liquid foods. Now emerged as a promising techniques having applications in food processing. This document will deliver the basics and applications of ultrasound in food
W.A. Mihiravi Pamuditha gave a presentation on radio frequency (RF) heating technology for food processing. RF heating uses electromagnetic energy to induce volumetric heating within foods. It has advantages over conventional heating like faster and more uniform heating. Some applications of RF heating in food include thawing, baking, drying, pasteurization and using RFID tags for tracking. While it has benefits, high equipment costs are a disadvantage. The future of RF technology may include its expanded use in continuous food processing and integration with technologies like nanotechnology and smart refrigerators.
This document discusses various methods of food concentration, including solar concentration, open kettles, flash evaporators, thin film evaporators, vacuum evaporators, freeze concentration, and ultra filtration and reverse osmosis. It also lists some commonly concentrated foods such as evaporated and sweetened condensed milks, fruit and vegetable juices, nectars, sugar syrups, flavored syrups, jams, jellies, and tomato paste. Additionally, it briefly introduces preservation by dehydration and mentions fruit juice powder.
Active packaging incorporates additives into packaging films or containers to maintain and extend the shelf life of food products. It includes oxygen scavengers, carbon dioxide generators, ethylene scavengers, and antimicrobial agents. Oxygen scavengers prevent food spoilage by chemically removing oxygen from packages through reactions with iron, ascorbic acid, or unsaturated fatty acids. Carbon dioxide generators and ethylene scavengers inhibit microbial growth and ripening to preserve freshness. Antimicrobial packaging prevents microbial growth through the release of compounds like ethanol or silver ions. Active packaging technologies are expected to grow significantly due to consumer demand for premium, safe, and convenient packaged foods.
This document discusses microwave technology in food applications. It begins by describing the properties of microwaves, including their wavelength and frequency approved for food. It then explains how microwaves are absorbed by polar molecules in food, causing heating through molecular friction. Microwave heating is described as uniform throughout the food, unlike conventional heating which occurs from the surface in. Several food applications of microwaves are listed, including baking, cooking, drying, and enzyme inactivation. The document concludes by noting the magnetron is commonly used to generate microwaves in microwave ovens and tunnel ovens.
Novel thermal technologies in food processingRahul1154
The document discusses novel thermal technologies for food processing, including microwave heating, infrared heating, and ohmic heating.
Microwave heating works by exciting water molecules in food, causing friction and generating heat. It is commonly used for drying, thawing, pasteurization, baking, and other applications. Infrared heating works by food absorbing infrared energy and converting it to heat, with the rate depending on surface properties. It is used for drying and processing. Ohmic heating passes electric current directly through food, generating heat from electrical resistance. It allows uniform, rapid heating and is used for pasteurization and other continuous processing.
Ankit Kumar presents information on novel food processing techniques. He provides details about his background and qualifications. The document then discusses several innovative processing methods including microwave heating, ohmic heating, irradiation, pulsed electric fields, and high pressure processing. It provides explanations of how each technique works and its advantages for food processing applications.
Microwave and radiofrequency processing are emerging food processing technologies. Microwaves have a frequency range of 300 MHz to 300 GHz and are used for applications like drying, cooking, and pasteurization. A microwave oven generates microwaves using a magnetron and consists of components like a waveguide and cooking cavity. Microwaves heat food through dielectric and ionic mechanisms. Radiofrequency uses frequencies from 1-300 MHz for applications such as blanching and dehydration. It induces volumetric heating through molecular reorientation and has higher penetration than microwaves. Both technologies provide advantages like faster and more uniform heating compared to conventional methods.
Microwave and radio frequency processing are methods of food processing that use electromagnetic waves. Microwaves range from 300MHz to 300GHz and heat food through dielectric heating and dipole rotation of molecules. Radio frequencies range from 20kHz to 3000GHz and heat food through dipole relaxation and ionic conduction. Both methods allow for uniform and rapid heating of foods. Microwave ovens use magnetrons to generate microwaves for heating while radio frequency equipment uses generators and electrodes. Applications include thawing, baking, pasteurization and drying. Advantages are high efficiency and uniform heating while disadvantages include high costs and difficulty controlling different food types and sizes.
This document discusses several new and emerging food processing technologies, including their principles, components, applications, advantages, and limitations. It covers technologies such as ohmic heating, microwave heating, pulsed electric field processing, high pressure processing, pulsed light technology, and ultrasound. These technologies aim to address issues with conventional thermal processing methods like nutritional losses, energy inefficiency, and longer processing times, while maintaining food quality and safety. They use techniques such as electrical currents, electromagnetic waves, high voltage pulses, high pressure, pulses of light, and ultrasonic waves to process foods.
Ohmic heating is a novel thermal food processing technique that uses electricity to rapidly and uniformly heat foods. It works by passing electricity through food materials, which act as resistors and generate heat. Key advantages are uniform heating from 1-100°C/s without hot surfaces, higher nutrient retention, and simpler controls than conventional heating methods. Ohmic heating has applications in meat processing, dairy pasteurization, fruit and vegetable blanching, and thawing. Further research is needed to address limitations such as potential metal contamination from electrolysis and difficulties heating non-conductive foods very high or low in moisture.
This document provides an overview of microwave heating technology presented by Kunwar Pratik Singh. It begins with an introduction to microwaves and their properties. It then discusses the principles of microwave heating through dipole rotation and ionic polarization. Key components of a microwave oven are described including the magnetron, waveguide and stirrer. Applications of microwave heating in various industries are listed. Advantages such as speed, energy efficiency and disadvantages like non-uniform heating are outlined. Research on improving heating uniformity through food shape and size is summarized. The conclusion discusses the growth potential for microwave processing.
Microwaves are produced inside the oven by an electron tube called a magnetron. The microwaves are reflected within the metal interior of the oven where they are absorbed by food. Microwaves cause water molecules in food to vibrate, producing heat that cooks the food.MW are electromagnetic waves generated by magnetrons and klystrons.
Frequency 300MHz and 300GHz
Wavelength from 1mm to 1m
industrial heating purposes the available frequencies are 915 and 2450MHz
MW giving up their energy to the material, with a consequential rise in temperature
Two imp mechanisms are:
Ionic polarization: conversion of kinetic energy of the moving ions into thermal energy
Dipole rotation: rotation of polar molecules leads friction with surrounding medium and heat is generated
ENERGY EFFICIENCY:
During microwave heating, electrical energy is first converted into microwave energy
The microwave then interacts with foods and is converted into heat
TWO EFFICIENCIES:
Microwave generation efficiency
Microwave absorption efficiency
ENERGY CONSUMPTION
Specific energy consumption was defined as the total energy supplied divided by the amount of water removed during drying
Overheating could increase the energy consumption due to high moisture loss from the overheated region
CONVERSION OF MICROWAVE ENERGY INTO HEAT
MW Heating is a consequence of the interactions between microwave energy and a dielectric material
PD= 55.61 X 10-14 f’ E2 ἐ tanᵹ
where,
PD Power dissipation W/cm3
f ‘ frequency in Hz
E electric field in v/cm (V/m)
ἐ relative dielectric constant
tanᵹ: loss tangent
MICROWAVE OVEN GENERALLY CONSISTS OF THE FOLLOWING BASIC COMPONENTS
(i) power supply and control: it controls the power to be fed to the magnetron as well as the cooking time
(ii) magnetron: it is a vacuum tube in which electrical energy is converted to an oscillating electromagnetic field. Frequency of 2450 MHz has been set aside for microwave oven for home use
Conti…..
(iii) waveguide: it is a rectangular metal tube which directs the microwaves generated from the magnetron to the cooking cavity
(iv) stirrer: it is commonly used to distribute microwaves from the waveguide and allow more uniform heating of food
(v) cooking cavity: it is a space inside which the food is heated when exposed to microwaves
Conti….
(vi) turntable: it rotates the food products through the fixed hot and cold spots inside the cooking cavity and allows the food products to be evenly exposed to microwaves
(vii) door and choke: it allows the food to the cooking cavity. they prevent microwaves from leaking through the gap between the door and the cooking cavity
FACTORS AFFECTING MICROWAVE HEATING
Dielectric properties
Temperature and frequency
Shape and size of food items
DIELECTRIC PROPERTIES
Penetration of microwave energy inside a material is a function of its dielectric properties.
Non thermal process in preservation of foodGazanfar Abass
The document discusses various non-thermal food processing techniques as alternatives to traditional thermal processing. It provides examples of different non-thermal methods like pulsed electric field, high pressure processing, pulsed light technology, microwave heating, ohmic heating, and irradiation. These methods allow for higher production rates and better retention of nutrients, flavors and quality compared to thermal processing. While the equipment costs are initially higher, non-thermal processing is increasingly being used in both large-scale and small-scale food industries.
Non thermal process in preservation of foodGazanfar Abass
The document discusses various non-thermal food processing techniques as alternatives to traditional thermal processing. It provides examples of different non-thermal methods like pulsed electric field, high pressure processing, pulsed light technology, microwave heating, ohmic heating, and irradiation. These methods allow for higher production rates and better retention of nutrients, flavors and quality compared to thermal processing. While the equipment costs are initially higher, non-thermal processing is increasingly being used in both large-scale and small-scale food industries.
Non thermal process in preservation of foodGazanfar Abass
The document discusses various non-thermal food processing techniques as alternatives to traditional thermal processing. It provides examples of different non-thermal methods like pulsed electric field, high pressure processing, pulsed light technology, microwave heating, ohmic heating, and irradiation. These methods allow for higher production rates and better retention of nutrients, flavors and quality compared to thermal processing. While the equipment costs are initially higher, non-thermal processing is increasingly being used in both large-scale and small-scale food industries.
The document discusses microwave assisted reactions for green chemistry. It begins with introducing green chemistry and its focus on reducing hazardous substances. It then discusses how microwave heating allows for faster, more energy efficient reactions by directly coupling with polar molecules. Key advantages of microwave heating include uniform and rapid heating throughout the reaction mixture. This leads to increased reaction rates, higher yields, and less waste generation compared to conventional heating methods. The document provides an overview of the mechanisms of microwave heating and its applications in organic synthesis.
Novel Thermal Technologies in Food Processing and Preservation.pptxRishabhThakur100
Thermal processing uses heat to reduce microorganisms in food and extend shelf life. Novel thermal technologies like microwave heating can process food faster at lower temperatures than conventional methods, preserving more nutrients and sensory qualities. Microwaves work by causing polar molecules like water to rotate, generating heat. Factors like moisture content, frequency, and product density affect microwave absorption and heating uniformity. Microwave processing offers advantages like shorter times, improved quality, and adaptability to continuous systems.
The document discusses emerging food processing technologies that can help reduce post-harvest losses of fruits and vegetables in India. It provides an overview of technologies like ohmic heating, microwave heating, pulsed electric field, high pressure processing, ultrasound, and pulsed light and explains their principles, components, applications, advantages, and limitations. These emerging technologies can help maintain the quality and safety of foods while being more energy efficient alternatives to conventional thermal processing methods.
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A comparative study between ohmic and microwave heating in food processing
1. A COMPARATIVE STUDY
OF OHMIC AND
MICROWAVE HEATING IN
FOOD PROCESSING
PRESENTED BY -
MARIAH SADAF
(13003417----)
SESSION- 2017-2021
2. INTRODUCTION
• Ohmic heating, a thermal electrical
heating method, is also termed as
resistance heating.
• Ohmic heating is direct heating method
where food is in contact with the
electrodes.
• The concept of ohmic heating is quite
simple. The passage of electric current
through an electrically conductive food
material obeys Ohm’s law (V = IR); and
heat is generated due to the electrical
resistance of the food.
• Almost all electric power is transformed
into heat.
• Microwaves are part of electromagnetic
spectrum in the frequency range falling
between radio and infrared region.
• Frequency 2450MHz – 915MHz(for
food)
• Microwave heating is a method that
offers technique of heating requiring
intermolecular friction ,conduction and
convection. Microwave generates heat
within the food rapidly raising the
temperature to the desired extent.
• The waves can be absorbed by water,
fat or sugar in foods and thus is
converted into Heat
OHMIC HEATING MICROWAVE HEATING
3. Increase In Kinetic Energy Thereby Heating The Product
Momentum Transfer To These Molecules
Collision Of Molecules
Conducts Electricity
Food Product
OHMIC HEATING
PROCESS DIAGRAMMECHANISM
4. The interaction
between the local field
strength and local
electrical conductivity
will govern the local
heat generation by
this equation
The actual heating
rate for the substance
can then be
calculated from the
equation
Q = E²k
= λJ²
Where Q is heat generation
rate per unit volume (W/m³)
E is the electric field strength
(V/cm)
k is the electrical conductivity
(S/m)
λ is the resistivity (ohm-meter)
J is the current density
(A/m²)
dT /dt =
Q/ ρC
Where T is temperature in degree
Celsius
t is the time in second
ρ is the density (kg/m³)
C is the specific heat
capacity(kJ/kg-
C)
ρC is the volumetric heat capacity
OHMIC HEATING
6. OHMIC HEATING
ADVANTAGES
DISADVANTAGES
High energy efficiency (90% electrical energy
is converted into heat).
Rapid and uniform heating
Better nutrient and vitamins retention
No theoretical upper temperature limit.
No hot surface for heat transfer; less risk of
surface fouling and burning of the product.
Reduced maintenance cost
Process can simply be controlled with switch
on and off.
Environmentally friendly.
Product with large size (15mm) and high
concentration of solid (up to 80%) can easily
be processed
Electrolysis of product and corrosion of
electrode occur at low frequency that may
result in metal contamination to food which
may be hazardous at high concentration.
Too high installation and initial operating
cost.
This system is unable to heat a product with
high fat and oil and dried food system. Since
fats are non-conductive (due to absence of
water and ions), it may bypass current and
slow heating may occurs.
Runaway heating may occur at high
temperature due to increase in electrical
conductivity.
8. MICROWAVE HEATING
The microwaves are generated by special oscillator tubes called "Magnetrons and Keltron”.
The electromagnetic energy, at microwave frequency is conducted through a coaxial tube or wave
guide at a point of usage.
Both Magnetron and Keltron are electron tubes which generate microwaves.
The Magnetron is a vacuum valve in which the
electron, emitted by the cathode, turn around
under the action of a continuous electric field
produced by the power supply and of a
continuous magnetic field. The movement
produces the electro-magnetic radiation.
Keltron uses the transit time between two given
points to produce this modulated electron stream
which then delivers pulsating energy to a cavity
resonator and sustain oscillation within the cavity.
1. Magnetron
2. Keltron
9. MICROWAVE HEATING : APPLICATION
Baking
Pasteurization and sterilization
Tempering
Blanching
Pre-cooking and Cooking
Dehydration
10. MICROWAVE HEATING
1. Low penetration depth
2. Product may hazardous to
health
3. High initial cost
4. Non uniform heating
5. Less energy efficient
1. Rapid heating
2. Reduced loss of nutrients
3. No contamination of foods
by products of combustion
4. Equipment is small,
compact, clean in operation
5. Surface of the food does not
overheat
6. Automatic process control
ADVANTAGES DISADVANTAGES
11. OHMIC HEATING MICROWAVE HEATING
Uses the electrical resistance of foods Forms of electromagnetic energy
Heat is generated due to electrical current Heat is generated by molecular friction
Depends on the electrical resistance of the food Depends on moisture content of the food
Penetrates throughout the food Limited penetration depth
12. SUGGESTIONS FOR IMPROVEMENT
Develop predictive, determinable and reliable models.
Reliable feedback control to adjust the supply power according to
the conductivity changes occurring.
Developing real time-temperature monitoring techniques for
locating cold-spots and overheated regions during heating.
Developing adequate safety and quality-assurance protocols in
order to commercialize these heating technology.
13. CONCLUSION
Thus, individually or in combination these two types of heating
methods are very beneficial in the food industry.
Helps in food preservation.
Increases the shelf life.
Inactivates microbes.
Gives the scope to bring about innovation in terms of
preservation.
High rate of heating during processing results in short
processing time.
Higher retention of nutrients and vitamins
Further research have to be carried out in order to identify
cold-spot, decrease cost and improve electrode so that
electrolysis is prevent
14. REFERENCES
• Microwave heating by By A.C. Metaxas
• Andrew Proctor, 2011. “Alternatives to Conventional Food Processing”. Royal Society of
Chemistry. 307-334.
• Ohmic heating in food processing. Ramaswamy, Hosahalli S. Boca Raton, FL: CRC Press.
2014.
• Varghese, K. Shiby; Pandey, M. C.; Radhakrishna, K.; Bawa, A. S. (October
2014). "Technology, applications and modelling of ohmic heating: a review"
• Ohmic Heating in food processing. CRC Press. 2014
• The Facts about Microwave Ovens by John R. Free, Popular Science, February 1973.
• Acierno, D., Barba, A. A., & d’ Amore, M. (2004). Heat transfer phenomena during
processing materials with microwave energy. Heat and Mass Transfer, 40(5), 413-420.
• Alajaji, S.A., & El-Adawy, T.A. (2006). Nutritional composition of chickpea (Cicer arietinum
L.) as affected by microwave cooking and other traditional cooking methods. Journal of
Food Composition and Analysis, 19, 806-812.
• Alibas, I. (2007). Microwave, air and combined microwave-air-drying parameters of
pumpkin slices. LWT-Food Science and Technology, 40, 1445-1451.
• Aparna, K., Basak, T., & Balakrishnan, A.R. (2007) Role of metallic and composite (ceramic-
metallic) supports on microwave heating of porous dielectrics. International Journal of Heat
and Mass Transfer, 50, 3072-3089