Pulsed Electric Field (PEF) applications can be utilised to achieve disintegration of biological tissues or microbes. Various applications have been identified such as improvement of mass transfer during extraction or drying as well as gentle food preservation. The first commercial applications of the technique have been achieved. By development of equipment based on state of the semiconductor, equipment reliability and cost effectiveness of the equipment has been improved. The technology is heading for wider industrial application.

1. Pulse electric field
Vinay Kaswan 115173
Viresh Gupta 115175
Vishal R 115176
Vishrut Sharma 115177
Anoop Jain 1115178
Avanish Parganiha 115179

2. Content:
 Theory
 Fundamentals
 Principle
 Mechanism
 Working
 Applications
 Limitations
 Case: sugar beet production
 Component
 PEF treatment chamber
 Commercially available PEF Machines
 Reference

3. Theory:

4. 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.

5. 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.
 PEF treatment is conducted at Ambient temperature ,
sub ambient temperature and slightly ambient
temperature.

6.  Provide consumer microbiological safe and minimally
processed foods.
 Physical properties of food is maintained.
 Energy lose due to heating of food is minimized.
 For food quality attributes, PEF technology is consider
superior to any traditional methods of food processing.
 Suitable for heat sensitive food items.
 PEF also called mild Preservation Technique

7. PEF processing has been studied
across a wide range of liquid
foods which includes-
 Apple juice and sauce
 Orange juice
 Yogurt
 Milk
 Tomato juice
 Carrot juice
 Pea soup
 Liquid whole egg and liquid egg products

8. Fundamentals of PEF

9. 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

10. Principle:

11.  The principle of this process is that the product is placed
between the two sets of electrodes and then delivered
electric current to food.
 The processing time = the no. of pulse*effective pulse
duration
 Food is capable of transferring electricity because of the
presence of several ions. So, when an electrical field is
applied, electrical current flows into the liquid food and is
transferred to each point in the liquid because of the
charged molecules present.
 The food product experiences a force per unit charge, the
so-called electric field, which is responsible for the
dielectric cell membrane breakdown in MOs & interaction
with the charged molecules of food
 This may cause temporary or permanent permeabilization of
cell membranes enables inactivation of vegetative cells of
bacteria and yeasts in various foods

13.  The electric field may be applied in the form of –
• Exponentially decaying,
• square wave,
• bipolar, or
• oscillatory pulses
 Processing temperature can be –
• at ambient,
• sub-ambient,
• slightly above-ambient temperature.

14. Mechanism of cell
inactivation

15.  The plasma membranes of cells become
permeable to small molecules after being exposed
to an electric field; permeation then causes
swelling and the eventual rupture of the cell
membrane.

16. Working:

17. 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 5-50 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.

18.  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
 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.

20. Applications

21.  Electro-permeabilization and cell disintegration, plays a
major role in food processing operations.
 Due to high intensity treatment, inactivation of
microbes can be achieved.
 Juice Processing
 PEF treatment of microalgae, PFE treatment of
seaweed, and other aquatic species
 Plant Oil Extraction
 Meat & Fish Treatment
 On microbial decontamination
 Sugar Processing

22. PEF in Plant Oil Extraction
 In fermentation and extraction of olives. PEF treatment
can be applied to raw olives at ambient temperature ,
leading to softening of the olive tissues. Also, PEF is
used for extraction of Maize germ oil and cotton seed
oil.
 The advantages of olive tissue softening are: easier
olive fermentation and cold extraction of oil.
 Advantages of PEF in Plant Oil Extraction are:
1) Increased oil extraction yield.
2) Higher process efficiency.
3) Improved oil quality.

23. PEF in Sugar Processing
 Benefits of PEF in Sugar Processing are:
1) Reduction of cutting force.
2) Higher extraction and refining yields.
3) Enhanced juice and sugar parity.
4) Continuous process and rapid technique.
5) Low energy requirement.
6) Enhanced product handling by tissue softening.
∙ In Sugar Processing using PEF, the pulse generator is
combined with a robust and hygienic transport system
and a PEF treatment chamber.

24. PEF in Juice Processing
 PEF treated juices are more closer to fresh juices based
on quality factors.
 Therefore, a clear conclusion drawn is that PEF has the
potential to become a suitable replacement to
conventional process if improvements in design are
applied.

25. PEF in Microbial
Decontamination
 The characteristics of the microbes to be inactivated
can impact the effectiveness of the PEF process.
 Several recent studies have been carried out on the
inactivation of pathogenic bacteria (such as E.coli and
Salmonella Enteritidis) inoculated in milk, egg and juice
products using PEF treatment, with the treated
products shown to be safe.
 This emerging technique can be used as integral part of
non-thermal pasteurization, or can be used in
combination with a hurdle method, depending upon the
characteristics of liquid food product.

26. Limitations :

27.  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

28. CASE:Sugar beet
production
An improved efficiency and reduction of energy input
and water use with pulsed electric field processing.

29. Pulsed Electric Field(PEF) processing of sugar beets for
sucrose extraction involves the application of
microsecond high voltage pulses in the order of 10 to 60
kV.
PEF causes tiny pore4s in the sugar beet cell walls , also
known as cell permeabilization, which facilitates sugar
leaching.

30.  By permeabilizing cell membranes of sugar beets, PEF
enables tissue softening and enhanced mass transport,
resulting in improved extraction of sucrose from sugar
beets, higher product quality and purity and increased
process capacity.

31.  Sugar beet processing becomes more homogenous with
PEF processing,evening the structure and resulting in
the reduction of seasonal variation in raw materials.As a
result, an improved refining efficiency and a significant
reduction of energy input and water use can be
measured.

32.  The new range of industrial scale equipment- named
conditioner- has treatment capacities from 1 ton an
hour to 50 tons an hour (about 110,00 lb/h) for sugar
beet processing systems.
 The pulse generator is combined with robust and
hygenic transport system and PEF chamber.

33. Input requirement of pef
 Microbial inactivation: 15-40kv/cm
 Sludge disintegration: 10-20kv/cm
 Improvement of mass transfer in plant/animal cell: 0.7-
3.0kv/cm

34. Components of PEF –

35. 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

36. System components of High
Intensity PEF Processing System
 The test apparatus in the continuous system consists of
different major components that are follows:
 1. High voltage power supply.
 2. Energy storage capacitor.
 3. A treatment chamber.
 4. A pump to conduct the food through the treatment
chamber.
 5. A cooling device.
 6. Temperature measurement devices.
 7. A computer to control the operation.

37. Continue…
 Energy from the power source is stored in the capacitor and is
discharged through the treatment chamber to generate an
electric field in the food material.
 The maximum voltage across the capacitor is equal to the
voltage across the generator .
 The bank of capacitors is charged by a direct current power
source obtained from amplified and rectified regular alternative
current main source.
 An electrical switch is used to discharge energy
(instantaneously in millionth of a second) stored in the
capacitor storage bank across the food held in the treatment
chamber.

38. Continue…
 A pump is used to convey the food through the treatment
chamber.
 A chamber cooling system may be used to diminish the ohmic
heating effect and control food temperature during treatment.
 High-voltage and high-current probes are used to measure the
voltage and current delivered to the chamber.

39. Fig. High Intensity PEF
Processing System

40. A PEF system for food processing in general consists of
three basic components :
- a high voltage pulse generator,
- a treatment chamber and
- a control system for monitoring
the process parameters .

42. Power supply
 The voltage increases by a transformer from line 220V
to high voltage 1000 to 5000V.
 It is rectified and stored in DC form in a capacitor by
the diode.
 Capacitor voltage is transformed to narrow pulses by
triggering signal and using the switch.
 the high voltage power supply is used to charge the
capacitor bank and store the energy to the capacitor
bank.

43. High-power capacitors
 Capacitance is the measure of the AMOUNT OF CHARGE DIFFERENTIAL
which builds up ACROSS a material when subjected to a voltage
differential.
 q = DV x C or DV = q / C
 I.e. Larger capacitance ----> Larger charge stored
 The energy stored in capacitors is used to generate electric or
magnetic fields.
 Electric fields are used to accelerate charged particles, leading to
thermal, chemical, mechanical, electromagnetic wave, or
breakdown effects.

45.  Transformer: Necessary output voltage is 1 we need a
transformer so that it can change line power 220V to
output selective voltage between 1-5 kV. Switching Power
supply supply has been used so that changing its frequency
tends to various voltages in the output
 Capacitor: The minimum desired load resistance is 150 ohm
Necessary maximum pulse width is 100µs; i.e. in the worst
situation, in interval of 100µs, the current of 33A must be
loaded. Assumed capacitor will be discharged after each
pulsing.
 Capacitors number: 32 So each four capacitors are series
together and package. All eight packages are fastened
parallel. Finally the capacitor bank resin insulated and
constructed with dimension 13*13*15cm. Diode: The diode
rectifies ac output of transformer in the form of semi-wave
and charges the capacitor. It should tolerate the current
that charges the capacitor.

46. Switches
 The discharging switch also plays a critical role in the
efficiency of the PEF system.
 In increasing order of service life, suitable switches for
PEF systems include: ignitrons, spark gaps, trigatrons,
thyratrons, and semiconductors.
 Solid-state semiconductor switches are considered by
the experts as the future of high power switching
(Bartos, 2000).
 High-power switching systems are the connecting
elements between the storage device and the load.

47. Continue…
 There are two main groups of switches currently
available: ON switches and ON/OFF switches.
 ON switches provide full discharging of the capacitor
but can only be turned off when discharging is
completed.
 ON switches can handle high voltages with relatively
lower cost compared to ON/OFF switches.
 however, the short life and low repetition rate are
some disadvantages to be considered for selection.
 The Ignitron, Gas Spark Gap, Trigatron, and Thyratron
are some of the examples from this group.

48. continue…
 ON/OFF type switches have been developed in recent
years that provide control over the pulse generation
process with partial or complete discharge of the
capacitors.
 Improvements on switches, mainly on semiconductor
solid-states witches, have resulted in longer life spans
and better performance.
 The gate turn off (GTO) thyristor, the insulated gate
bipolar transistor (IGBT), and the symmetrical gate
commutated thyristor (SGCT) are some examples from
this group

50. High voltage pulse generator
 The high voltage pulse generator provides electrical pulses of the
desired voltage, shape and duration by using a more or less
complex pulse forming network (PFN).
 PFN is an electrical circuit consisting of several components:
- one or more DC power supplies,
- a charging resistor,
- a capacitor bank formed by two or
more units connected in parallel,
- one or more switches, and
- pulse-shaping inductors and resistors.
- The DC power supply charges
the capacitors bank to the desired voltage.

51.  Using this device, the ac power from the utility line (50-
60Hz) is converted in high voltage alternating current
(A) power and then rectified to high voltage dc power.

53. Pump & Piping Used in PEF
 To Bring liquid or semi liquid product from raw product
tank to treated product tank.
 Postive Displacement pumps or peristaltic pumps are
commonly used.
 Continuous or pulseless pumps are preferred to ensure
treatment homogeneity.
 Stainless steel piping is preferred for sanitary reason.
 No restriction exist for the use of other types of pumps.

54. Control And Monitoring
Devices
 PEF System are usually hooked up to a central computer
that control the operation of
- high voltage pulse generator
- voltage and pulsing frequency
- operation of pumps and
electric valves
 Computer also records data logs which includes
temperature at several points, flow rate of product,
voltage, currents and power curves applied pulses.
 Commercially available sofwares that can be used in PC
to administer the control and data gathering process-
HP V Lab® or Lab view®.

55. PEF Treatment
Chamber

56. PEF Treatment chamber :
 The basic idea of the treatment chamber is to keep the
treated product inside during pulsing, although the
uniformity of the process is highly dependent on the
characteristic design of the treatment chamber.
 A treatment chamber usually consists of two electrodes
held in position by an insulating material which also
forms an enclosure containing the sample to be
processed.

57.  For proper designing of chamber the electrical
properties of slurries have to be treated and fluid
dynamic aspects related to the flow of viscous material
are to be considered.
 Treatment chamber must guarantee the homogenous
and continuous Pulse Electric Field (PEF) treatment of
food material.
 Several different treatment chambers have been
proposed. Example: parallel plate, concentric cylinder,
and co-field.

58.  These chambers have been designed for inactivation
purposes of treating almost all liquid foodstuff and thus
homogenous material. In such cases, the presence of
solid particles in food material has been considered in
determining the chamber configuration.
 The principal requirement to the guaranteed in
designing a treatment chamber is the homogeneity of
the generated electric field.
 Homogeneity of the electric field exists throughout the
gap between the electrodes, in fact, it ensures
homogenous treatments.

59. The design of the treatment chamber is an important
parameter for microbial inactivation and must conform to
several specifications:
 The treatment chamber should resist high current intensity.
 The distribution of electric field in the treatment chamber
should be as uniform as possible.
 `Dead zones' (absence of electric field or of sample
circulation) should be avoided.
 Dielectric breakdown (arcing) should be avoided since it
would induce nonuniform processing and local overheating
of the sample. It can be induced by local field
enhancement on an electrode, electric tracking along an
insulator surface and/or the presence of gas bubbles in
samples.
 The materials used should minimise electrochemical
phenomena at the electrodes.

60. PEF Treatment Chamber
Design:
 Treatment chambers are mainly grouped together to
operate in either a batch or continuous manner; batch
systems are generally found in early designs for handling
of static volumes of solid or semi-solid foods.

62. Batch Systems:
They are majorly of two types:
1) Parallel plate electrode chamber:
 This consists of two electrodes supported on brass
blocks placed in a U-shape polystyrene spacer.
 Different spacers regulate the electrode area and
amount of food to be treated.
 This chamber could support a maximum electric field of
30kV/cm.

63. 2) Glass coil static
chambers:
 This model uses a glass coil surrounding the anode.
 The volume of chamber is 20 cubic cm.
 The liquid media used is NaCl solution, with σ= 0.8 to
1.3 S/m, because there is no inactivation with a non
conductive medium.

64. Continuous flow systems:
 Continuous flow PEF treatment chambers are suitable
for large scale operations and are more efficient than
static chambers.
There are majorly four types of continuous flow systems:
 Parallel plate chamber
 Co-field flow chamber
 Coaxial continuous PEF chamber
 Enhanced electric field continuous treatment chamber

65. Continuous PEF system

66. PEF system with multiple
treatment chamber

67. 1. Parallel plate chamber:
 They were first designed to treat a confined, static volume.
 This design incorporates parallel plate geometry using flat electrodes
separated by an insulated spacer.
 Due to the electric field strength limitation it is difficult to increase
product load and this made this chamber more efficient.
 The major disadvantage of this type of design is the low productivity of
these cambers.

68.  The parallel plate treatment chamber consists of two stainless steel
plate electrodes and a Teflon insulator.
 The insulator is cylindrical and presents internal square cross section
cavities in which the two electrodes are placed.
 Two side holes allows the electrical connection of the electrodes with
the pulser. The chamber consists of two symmetric halves, easily
opened for cleaning.

69. 2. Co-field flow chamber:
 These chambers have two hollow cylindrical electrodes
separated by an insulator to form a tube through which the
product flows.
 Field distribution in co-field flow chamber is not expected to
be uniform, though some useful advantages may be gained by
special shaping of the insulator.
 The primary advantage of ci-field chamber is that they can be
designed to operate in PEF systems at lower currents than
coaxial chambers.

71. 3. Coaxial continuous PEF chamber:
 They are generally composed of an inner cylinder surrounded
by an outer annular cylindrical electrode that allows food to
flow between them.
 A protruded outer electrode surface enhances the electric
field within the treatment zones and reduces the field
intensity in the remaining portion of the chamber.
 Using the optimized electrode shape, the prescribed field
distribution along the fluid path without an electric field
enhancement point was determined.
 This chamber can be used in inactivation of pathogenic and
non-pathogenic bacteria, molds, yeasts and enzymes present
in liquid foods.

73. 4. Enhanced electric field
continuous treatment chamber:
 In this we apply the concept of enhanced electric fields
in the treatment zones by development of continuous
co-field flow PEF chamber with conical insulator shapes
to eliminate gas deposits within the treatment volume.
 The conical regions were designed so that the voltage
across the treatment one could be almost equal to the
supplied voltage.

75. Reference
 Mirzaee, H., & Pourzaki, A. (2011). Designing and
Manufacturing High Voltage Pulse Generator with
Adjustable Pulse and Monitoring Current and
Voltage: Food Processing Application. World
Academy of Science, Engineering and Technology,
International Journal of Electrical, Computer,
Energetic, Electronic and Communication
Engineering, 5(12), 1910-1915.
 Mohamed, M. E., & Eissa, A. H. A. (2012). Pulsed
electric fields for food processing technology.
In Structure and function of food engineering.
InTech.

76.  Handbook of Food Science, Technology,
and Engineering
 Novel Food Processing Technologies
 De Vito, F. (2006). Application of pulsed electric field
(PEF) techniques in food processing. Rozprawa
Doktorska, UNIVERSITÀ DEGLI STUDI DI SALERNO.

77. Thank you.