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.
Radio frequency processing and Microwave heating in food processing prakashsp13
radio frequency and microwave heating ; these slides are explain about its principle and working mechanism ,application in food processing and its advantages .
Microwave heating has gained popularity in food processing due to its ability to achieve high
heating rates, a significant reduction in cooking time, more uniform heating, safe handling, ease
of operation and low maintenance.
Thus, food industry is said to be the largest consumer of microwave energy, where its
application has been utilized in thawing, baking, dehydration, melting, tempering, and
pasteurization, sterilization, heating, and re-heating, etc.
Microwave (MW) energy is a form of radiation. The term radiation means that the energy is
transported by the force fields of electromagnetic waves; they can radiate through a perfect
vacuum and do not need any medium to transfer energy from one object to another. All
electromagnetic waves have two components
1) Electric field 2) Magnetic field
Radio frequency processing and Microwave heating in food processing prakashsp13
radio frequency and microwave heating ; these slides are explain about its principle and working mechanism ,application in food processing and its advantages .
Microwave heating has gained popularity in food processing due to its ability to achieve high
heating rates, a significant reduction in cooking time, more uniform heating, safe handling, ease
of operation and low maintenance.
Thus, food industry is said to be the largest consumer of microwave energy, where its
application has been utilized in thawing, baking, dehydration, melting, tempering, and
pasteurization, sterilization, heating, and re-heating, etc.
Microwave (MW) energy is a form of radiation. The term radiation means that the energy is
transported by the force fields of electromagnetic waves; they can radiate through a perfect
vacuum and do not need any medium to transfer energy from one object to another. All
electromagnetic waves have two components
1) Electric field 2) Magnetic field
What is hurdle technology,
Introduction to hurdle technology
Need of hurdle technology
Hurdle effects
How it work in food industry
Types of hurdle used in food preservation.
High pressure processing (HPP) is a method of preserving and sterilizing food, in which a product is processed under very high pressure, leading to the inactivation of certain microorganisms and enzymes in the food
What is hurdle technology,
Introduction to hurdle technology
Need of hurdle technology
Hurdle effects
How it work in food industry
Types of hurdle used in food preservation.
High pressure processing (HPP) is a method of preserving and sterilizing food, in which a product is processed under very high pressure, leading to the inactivation of certain microorganisms and enzymes in the food
Study On dehydration of Papaya Slices Using Osmotic Dehydration Mediated Hot ...iosrjce
IOSR Journal of Environmental Science, Toxicology and Food Technology (IOSR-JESTFT) multidisciplinary peer-reviewed Journal with reputable academics and experts as board member. IOSR-JESTFT is designed for the prompt publication of peer-reviewed articles in all areas of subject. The journal articles will be accessed freely online.
Micro-organisms need water in order to grow and reproduce. When moisture is removed from food, it does not kill the microbes but it does stop their growth. Dehydration reduces the water activity level, weight and the bulk of the food and helps to preserve the product.
Freeze Drying merupakan metoda pengawetan produk pangan agar dihasilkan produk yang memiliki stabilitas pada strukturnya baik secara kimiawi ataupun biologi. Sistem yang terdapat dalam Freeze Dryer (alat/mesin Freeze Drying) pun tentu sangat kompleks. Saat ini banyak industri yang menggunakan metoda ini, tidak hanya bahan pangan, tetapi juga bisa untuk bidang farmasi dan boiteknologi, dekorasi, makanan astronout, penyimpanan dokumen, dll.
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.
A microwave oven, is a kitchen appliance that can come in many different sizes and styles employing microwave radiation primarily to cook or heat food. This is accomplished by using microwaves, almost always emitted from a magnetron, to excite water (primarily) and other polarized molecules within the food to be heated. This excitation is fairly uniform, leading to food being heated everywhere all at once
A microwave oven, is a kitchen appliance that can come in many different sizes and styles employing microwave radiation primarily to cook or heat food. This is accomplished by using microwaves, almost always emitted from a magnetron, to excite water (primarily) and other polarized molecules within the food to be heated. This excitation is fairly uniform, leading to food being heated everywhere all at once
1. Microwave In Food
Technology
By
Nivedha Mohanan
B.Tech Food Tech
Amity University
Jaipur
2.
3. Microwaves: Properties
General
•Electromagnetic waves of radiant energy
•Wavelength: 0.025-0.75(m)
•Frequency: 20,000-400(MHz)
Specific to Food Applications:
•Frequency Approved for Food Application: 2450MHz & 915MHz
•Reflected by metals, pass through the air, absorbed by several food
constituents
4. • Absorbed material heated up to the extent of absorption. Microwave
loses heat in the process.
• Loss factor and loss tangent used to define the loss of Microwave
energy.
• Materials that are highly absorbent of microwaves are called ‘highly
lossy’ materials.
• Loss Factor is also a measure of the degree of the penetration of the
microwave. The greater the loss, the more the heat produced and
lesser the penetration.
• According to these properties the microwave frequency is chosen.
5. Mechanism of Microwave Heating
• Microwave reverses its directions corresponding to frequencies of either
915MHz or 2450MHz.
• Food and certain other materials acts as dipoles. Ex: Water.
• When microwaves pass through the food, water and other polar molecules
try to along themselves with the electric field which changes at least 915
times a second.
• This leads to intermolecular friction, which in turn causes heating.
• As different components of food have different heating factors, it takes
simultaneous conduction(solids) and convection(liquids) to equalize the
distribution.
• The conduction and convection are the secondary effects while
intermolecular frictional heat is the primary effect.
6.
7. Microwave & Conventional Heating:
The Differences
Conventional
•A direct flame, heated air, etc used in the conventional heating.
•Food molecules largely react from the surface inwards, producing a heating
gradient.
•This can lead to difference in the burning of food surface and interiors.
Microwave
•Microwaves penetrate up to a few centimetres of the food which heats the
food uniformly.
•Heat is passed in from surface by conduction but is generated quickly and
uniformly throughout the mass.
•Hence the moisture is boiled away internally.
8. • Microwave heating thus leads to no crusting and surface browning.
• This is a limitation when a crust on the surface is desired. For ex,
bread baking.
• In such a case, the microwave heating is accompanied by or followed
or preceded by a conventional heating methods.
9. Microwave Generators and Equipment
• Most commonly used microwave generator is Magnetron.
• It is a kind of electron tube within a magnetic field which propagates high
frequency radiant energy.
• Power output is measured in kwatts. Larger the power, better the heating.
• Also, the weight of the food also determines the heating time of the food.
• Simple Microwave oven is a metal cabinet into which the Magnetron is
attached.
• Food is attacked by the oven and thus the food gets heated from all forces.
10.
11. • Complex microwave tunnel oven are equipped with an endless
moving belt of low loss material on which food is conveyed past
magnetrons.
• Open at inlet and exit for transfer of food.
• Trapping of microwaves is done by providing heat absorbing food
which absorb any stray radiation.
• Possible to heat liquid resources. Liquid maybe pumped through low
loss coil of glass or kept near to microwave.
12.
13. Microwave Food Applications
• Baking
Internal heating quickly achieves desired temperature throughout the
product. Often combined with external heating.
• Concentrating
Permits concentration of heat sensitive solution and slurries at
relatively low temperatures in relatively low time.
• Cooking
Microwaves cook large pieces without high temperature gradient
between the surface and interior. Suited for continuously cooking of
file.
14. • Curing
Effective for glue line curing of laminates without direct heating of the
laminates themselves.
• Drying
Microwaves selectively heat water with little direct heating of the
solids.
• Enzyme Inactivation
Rapid uniform heating to inactivating control can control and terminate
at enzymatic reactions.
• Finish Drying
Used to remove excess traces of water after using conventional heating
without overheating the system.
15. References
• All the data or text input is derived from the Food Science belonging
to Food Science Text Series.