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pulse electric field
1.
2. PULSED ELECTRIC
FIELD
Pulse:-
A pulse is a single disturbance that moves
through a medium from one point to the next
point.
A disturbance is in some identifiable medium.
Energy is transmitted from place to place, but the
medium does not travel between two places.
3. What is pulsed electric
field?
Pulsed electric field (PEF) used short electric
pulses to preserve the food.
Pulsed electric field (PEF) treatment is an
innovative and promising method for non-thermal
processing of foodstuff.
It is suitable for preserving liquid and semi-liquid
foods removing micro-organisms and producing
functional constituents.
Examples:- milk, fruit juices, soup, egg etc.
4. Fundamentals of PEF
PEF : Generation of very high intensity electric pulses
(up to 15kV), for a very short duration of time (μs)to
inactivate microorganisms
6. About of PEF
It is one of the most appealing technology due to
:-
-short treatment time(typically below 1 second).
-reduced heating effect.
-energy lost during heating food is minimized.
-for fresh-like characteristics of food, along with
high sensorial quality and nutrient content
7. How does this technology benefit
consumers ?
PEF processing offers high quality fresh-like liquid
foods with excellent flavor, nutritional value, and shelf-
life.
Since it preserves foods without using heat, foods
treated this way retain their fresh aroma, taste, and
appearance.
8. Components of PEF
– Pulse generator
High voltage power supply
HV transformer
Capacitor (storing energy)
Switching devices
– Fluid handling system
Pumping mechanism (batch or continuous)
Treatment chambers
– Cooling mechanism
– Oscilloscope (to measure the changing of voltage with
time)
– Computer
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13. How does PEF work to inactivate microorganism
PEF technology is based on a pulsing power delivered to the
product placed between electrodes by high voltage pulses in the order
of 20–80 kV (usually for a couple of microseconds).
The equipment consists of a high voltage pulse generator and a
treatment chamber with a suitable fluid handling system and
necessary monitoring and controlling devices.
Food product is placed in the treatment chamber, either in a
static or continuous design, where two electrodes are connected
together with a nonconductive material to avoid electrical flow
from one to the other
Generated high voltage electrical pulses are applied to the
electrodes, which then conduct the high intensity electrical pulse
to the product placed between the two electrodes.
The food product experiences a force per unit charge, the so-
called electric field, which is responsible for the irreversible cell
membrane breakdown in microorganisms.
14. This leads to dielectric breakdown of the microbial cell
membranes and to interaction with the charged molecules of
food.
Hence, PEF technology has been suggested for the
pasteurization of foods such as juices, milk, yogurt, soups, and
liquid eggs.
15. How are PEF processed foods stored ?
PEF pasteurized products currently are stored
refrigerated.
In some cases (for example, milk), this is
necessary for safety (to prevent the growth of
spores in low-acid foods).
For acid foods, refrigeration is not necessary for
microbial stability, but is used to preserve flavor
quality for extended periods of time.
16. The economics of PEF
processing ..
PEF is an energy efficient
process compared to thermal
pasteurization.
The PEF processing would add
only $0.03–$0.07/L to final food
costs.
A commercial-scale PEF system
can process between 1,000 and
5,000 liters of liquid foods per
hour and this equipment is
scalable.
17. To Obtain Safe and Healthy
Shelf-Stable Liquid Foods
The shelf-life of a PEF processed product
In general, the shelf-life
of PEF-treated and thermally
pasteurized foods is comparable.
PEF pasteurization kills microorganisms
and inactivates some enzymes
and, unless the product is acidic,
it requires refrigerated storage.
18. For heat-sensitive liquid foods where thermal
pasteurization is not an option (due to flavor, texture,
or color changes), PEF treatment would be
advantageous.
19. The integration of continuous PEF Processing
System ..
An integrated PEF system consists of a fluid handling
unit, high voltage pulse generator, PEF treatment
chambers, and packaging machine.
The fluid handling unit delivers stable, uniform flow
with sterilize-in-place (SIP) and clean-in-place (CIP)
functions.
The pulse generator supplies high voltage pulses into
foods flowing through PEF treatment chambers.
Treated foods are packaged continuously.
20. What is a PEF treatment
chamber ?
A PEF treatment chamber consists of
at least two electrodes and insulation
that forms a volume, i.e., PEF treatment
zone, where the foods receive pulses.
The electrodes are made of inert
materials, such as titanium .
23. Is commercial scale equipment available ?
In the United States, the first commercial scale
continuous PEF system is installed at The Ohio State
University’s Department of Food Science and
Technology.
This PEF system processes volumes ranging from 500
to 2,000 liters per hour.
Is PEF equipment safe for the environment?
Yes, this process uses ordinary electricity. The facility
meets electrical safety standards and no harmful
environmental by-products are produced.
24. Limitations :-
No effect on enzymes and spores
Difficult to use with conductive materials
Only suitable for liquids or particles in liquids
Only effective in combination with heat
Products of electrolysis may adversely affect foods
Safety concerns in local processing environment
Energy efficiency not yet certain
May be problems with scaling-up process
25. Engineering Principles
C0=τ/R=τσA/d
τ=pulse duration (s)
R=resistance (Ω)
σ=conductivity (S/m)
d= gap between electrodes (m)
A=area of electrode (m2)
Q=0.5 C0 V2
Q=energy stored in capacitor (J/m3)
C0= Capacitance (F)
V= charging voltage
