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.

1. MICROWAVE AND
RADIO FREQUENCY
PROCESSING
Guided By:
Dr. Anil Kumar
Sir.
Submitted By:
Bijjam Madhavi
MSc. Food Technology

2. FOOD PROCESSING…
• A simple definition of food
processing is the conversion of raw
materials or ingredients into a
consumer food product.
• Commercial food processing “ is
defined as that branch of
manufacturing that starts with raw
vegetable, animal or marine
materials and transforms them into
intermediate food stuffs or edible
products through the application of
labour, machinery, energy and
scientific knowledge”.

3. MICROWAVE PROCESSING…
Microwaves are the shortest
wave length region of the
spectrum and a part of the
electromagnetic spectrum.
Electromagnetic waves
frequencies range from
300MHz – 300GHz or
wavelengths in air ranging
100cm – 1mm.

4. PROPERTIES OF MICROWAVE…
Electromagnetic
radiation of short
wavelength.
Reflected by
conducting
Not reflected by
ionosphere.

5. MICROWAVE OVEN…
A microwave is a
appliance that cooks
heat food by dielectric
heating.
It is accomplished by
using microwave
radiation to heat
and other polarized
molecules in the food.

6. HEATING MECHANISM…
Ionic
interacti
Dipolar
interacti
Heat
generati

7. PARTS OF EQUIPMENT:
Temperatur
e Indicator
Door
Cooking Cavity
Turntable
Magnetron
Oven Cavity
Wave Guide
Stirrer
Power Cord

8. MICROWAVE HEATING EQUIPMENT…

9. MICROWAVE GENERATION…
The microwaves are generatd by special oscillator tubes
called “magnetrons” . These are devices that convert low
frequency electrical energy into hundrends and thousands
of megacycles. The electromagnetic energy, at microwave
frequency is conducted through a coxial tube or waveguide
at a point of usage.
Magnetron: It is a cylindrical diode with a ring of resonant
resonant cavities that acts as a anode structure. The cavity is
the space in the tube which becomes excited in a way that
makes at a source for the oscillation of microwave energy.
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
electromagnetic radiation.

10. ADVANTAGES AND APPLICATIONS…
Speedy
Clean
Smell
free
Less
washing
up
Thawing
Nutritionally
sound
Easy to
use
Cool

11. DISADVANTAGES…
Because of speed, and the way in which
microwave energy cooks, food cooked in
a microwave oven will not be brown, so
no crust formation.
High initial cost.
Short cooking time does not allow
flavours to develop and this makes food
unacceptable.

12. RADIO FREQUENCY…
Radio frequency is the
oscillation rate of an
alternating electric current
or voltage or of a magnetic,
electric or electromagnetic
field or mechanical system
in the frequency range
from around 20KHz to
around 3000GHz.
Radio frequency heating
is the electrical energy is
firstly converted to
electromagnetic radiation
which subsequently
generates the heat with in
the product.

13. PRINCIPLE OF RADIO FREQUENCY…
RF heating is a combination of dipole heating and electric resistance
heating resulting from the movement of dissolved ions present in the food.
RF with the electromagnetic waves in 30-3000MHz spectrum added
advantage of uniform heating in homogenous foods, high penetration depth
used to pasteurize or sterilize liquid products.
The mechanism of RF heating is that the molecules within a product placed
in an RF environment reorient themselves continuously in response to the
applied field.
This response initiates the volumetric heating with in the entire product due
to frictional interaction between the molecules, thus selectively heats only
the product and not the air or equipment surrounding it.

14. RF HEATING SETUP…

15. RF HEATING OF PARTICLES…

16. RF HEATING MECHANISM…
In radio
frequency
heating
system, the
RF generator
creates an
alternating
electric field
between two
electrodes.
The material to
be heated is
placed in
between the
electrodes where
the alternating
energy causes
polarization of
the molecules,
thus
continuously
reorient
themselves to
face opposite
poles.
The energy
absorption
involves:
Primary two
two
mechanisms
– dipolar
relaxation
and ionic
conduction
Water in the food
is often the
primary
component
responsible for
dielectric heating.
Due to their
dipolar nature,
water molecules
try to follow the
electric field
associated with
electromagnetic
radiation as it
oscillates at very
high frequencies,
thus producing
heat.

17. CONT….
Secondary
mechanism of
heating is through
the oscillatory
migration of ions
in the food that
generates heat.
The amount of heat
generated in the
product is determined
by :
(a)frequency,
(b)the square of the
applied voltage,
(c) dimensions of the
product and
(d) the dielectric loss
factor of the material.
RF power is
produced when
electricity is
applied to an RF
generator whose
signal is amplified
and delivered to a
parallel electrode
system, in which
selected material
is placed.

18. RADIO FREQUENCY EQUIPMENT…

19. APPLICATIONS…..
Thawing
Baking
Pasteurization/
Sterilization.
Drying

20. ADVANTAGES…
High
energy
transfer
efficiency.
Uniform
heating
with in the
product.
Short
process
time.
Reduced
equipment
dimension.
Instant and
accurate
process
control.
Better
preservation
of sensorial,
chemical and
physical
characteristic
s of the
product.

21. DISADVANTAGES…
The cost of electronic
components used in this
technique is quite high.
Energy consumption is
higher.
Different products will
require different heating
process time due to their
shape, size, dielectric
material, position etc…

22. CONCLUSION…
• MICROWAVE FREQUENCY
 Microwave cooking range is soon taking up a key role as one of the daily use home
appliances in Indian homes.
 Available in almost all electronic shops, they are becoming essential for the
working families in India.
 The price of microwave oven is less.
• RADIO FREQUENCY
 The industrial application of RF is still limited towards meat, disinfectant of
agricultural commodities and post baking.
 RF power provides a greater challenge to engineer to develop large scale
production unit for industrial application.
 RF heating system can take the modern market on food processing without any
reason of concern.

23. • REFERENCES:
 Brittany, H. Microwave synthesis.
 Matthews, chemistry at the speed
light.
 Microwave energy and its
in food nindustry by Adarsh M.
 Youn KS , Radio frequency
 Zhang, L. , Quality of radio
heated.
 Wang J, Radio frequency heating
heterogeneous food.