pulse electric field

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

5. Input
requirements
of PEF
Microbial
inactivation
15-40kV/cm
Improvemen
t of mass
transfer in
plant/animal
cell
0.7-3.0kV/cm
In apple juice
22-34kV/cm
Sludge
disintegration
10-20kv/cm

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

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 .

21. Continuous PEF system

22. PEF system with multiple
treatment chambers

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