High voltage pulse technique or High intensity pulsed electric field processing involves the application of electric pulses of high voltage 20-80 kV/cm to the food placed between two electrodes. The applied electric field create a pores on the cell membrane, thus the phenomenon known as Electroporation or electropermeabilization. The effect of Electroporation can be divided into four steps: An increase in the transmembrane potential Pore formation Evolution of the number and size of the pores Pore resealing

1. HIGH VOLTAGE PULSE TECHNIQUE-INACTIVATION OF
MICROORGANISM,ELSTERIL PROCESS-ELECTROPORATION
PROCESS-TYPE OF WAVE FORMS.EQUIPMENTS USED IN
PULSED ELECTRIC FIELD PROCESS-CONSTRUCTION DETAILS-
VOLTAGE AND POWER CONSUMPTION.

2.  Non thermal method for food preservation
 Uses short pulses of electricity for microbial inactivation
 Cause minimal detrimental effect on food quality.
 It offer consumers high-quality foods

3.  High voltage pulse technique or High intensity
pulsed electric field processing involves the
application of electric pulses of high voltage
20-80 kV/cm to the food placed between two
electrodes.
 The applied electric field create a pores on the
cell membrane, thus the phenomenon known as
Electroporation or electropermeabilization.

4. Electropure process: In 1920s and 1930s electropure
process was introduced in Europe and US, it was 1st
attempt to use electric field to inactivate microorganism.
 Pasteurization of milk using electric field of 220V
alternating current and not pulsed. Which is similar to
ohmic heating.
Electrohydraulic treatment: In 1950s, this method was
developed to kill microbes using high voltage electricity-
electrodes producing shock waves of 1000 bars-
submerged in the liquid containing micro-organism.

5.  Sale and Hamilton- 1st conducted systematic studies on
PEF.
 They showed that electric strength and treatment time were
the two most important factors in PEF.
 By suspending impermeable microorganism in a gel, they
proved that insignificance of electrolysis on the lethal effects
of direct current (DC) pulses.
 All their experiment temperature were below 10°C,so they
conclude that the inactivation was not due to thermal effect.
 They reported that, PEF cause loss in motility and inhibited
synthesis of enzymes but not the enzymes already present
in it.

6. Lab scale PEF system Pilot scale continuous
flow system.
(University of Salerno,
Italy)
Pilot facility (Karlsruhe;
Germany) for PEF
treatment of dense
cell suspensions at a
mass flow of 400 l/h.

8.  When the cell is exposed to external electric field the
Electroporation process conducted at ambient temperature
for less than 1s. The effect of Electroporation can be divided
into four steps:
1. An increase in the transmembrane potential
2. Pore formation
3. Evolution of the number and size of the pores
4. Pore resealing

9. 1. An increase in the
transmembrane
potential
• The cell membrane is considered as a dielectric material of
low electrical conductance.
• accumulation of charges on both sides of the membrane
leads to a naturally occurring, perpendicular transmembrane
potential of about 10mV
•When the electric field applied to the cell membrane, an
additional potential is induced and increasing it up to a
maximum value

10. Schematic depiction of the formation of hydrophilic pores in the cell
membrane.

11.  The number and size of pores totally depends upon the
amount of electric field applied.
 Nanosecond duration pulse cause smaller pores in a
larger numbers than the millisecond duration pulse
 Higher amplitude and longer pulses increase number
and size of pores.
 Factor influencing- Temperature

14.  It requires slow charging and rapid discharging of the
energy, as the pulse width is short comparison with the
time between the pulses.
 Many devices can be used as discharge switch vacuum or
gas sparks, high power transistors, thyratrons or
semiconductor switches.
 Type of switch determines maximum repetition rate.

15. Electric field strength E is given by,
E= U/d
where,
U = voltage (kV)
d = gap between the electrodes (m)
If the gap d gets increased to obtain high flow rate capacity, the
charging voltage also get increased.
ELECTRODE MATERIAL:
The electrodes are made up of stainless steel (type 316) with
a gap 2 mm.
Electrode material composition:
Iron, chromium, nickel, molybdenum and manganese.

16. Exponential decay pulse Square wave pulse

17.  Exponentially decaying, square wave, bipolar or
oscillatory pulses.
 Square wave pulses maintain a high voltage for the total
impulse width.
 Exponential have a long tail with low electric field.
 Both the type effective for microorganism.
 Square wave pulses save energy and requires less
cooling effort.
 An industrial application for production of pulses
required:
High voltage - 40-100 kV
Current level - 100A-5kA

19.  The process were developed by Krupp Maschinentechnik.
 Components of ELSTERIL process plant:
Pulse generator
Discharge chamber
Sample to be treated

20. •Krupp developed the Elsteril process for inactivating
vegetative microorganisms in milk and fruit juices with
electric field strengths of upto 30kV/cm.
• While considering this process for industrial application
flaws were found in:
Heating due to high energy dissipation
High operational cost
•Flaumenbaum report that while applying electric field for
electroplasmolysis of apple mash, observed that there is:
Increase in 10 to 12% of juice yield,
Products were lighter in colour,
Less oxidized than after a heat or enzymatic
Pre treatment.

21.  Electric field strength
 Treatment time
 Pulse geometry
 Treatment temperature
 Air bubbles
◦ Cannot withstand high
electric field strength
◦ current flow within the
bubble instead of liquid
◦ Foam forming products
unsuitable
 Treatment medium factors
(e.g. resistant microbes)
 Conductivity ( ionic
species).
 pH ( acidic gram -ve
bacteria PEF resistant)
 Physical and chemical
parameters of product
 Cell characteristics
(membrane composition of
different microbes influences
their resistivity)
PEF combined with heat
treatment is used to eliminate
it.
PROCESS AND PRODUCT
PARAMETERS

22.  Pasteurization
 Extraction
 Pre-treatment
 Cutting
 Peeling
 Liquid foods
 Solid foods
 Non food application

23.  pasteurization of foods such as juice, milk, yogurt, soup, liquid
eggs and any other pumpable food products
 enhance extraction of sugars and other cellular content from
plant cells, such as sugar beets.
 Extraction of high quality pectin from the pomace after
extracting the juice
 The less color change in fruit juices, less browning in juices
treated by PEF

24.  The typical average power of a PEF unit is in a range of
20-400 kW.
 In grapes an enhanced release of anthocyanins and bioactive
substances has been reported through the use of PEF.
PRE TREATMENT:
 PEF induced release of intracellular moisture also allows
acceleration of drying processes.
CUTTING:
 PEF-induced membrane permeabilization results in the loss of
turgor pressure (water potential) and significant tissue
softening.
 An improved cutting of potatoes were observed in the applied
PEF of 1-2 kJ/kg and also causing less fracture and smooth cut
surfaces.
 improve the cutting quality for industrial production of French
fries

25. PEELING:
 PEF can enhance peeling of fruits and vegetables, like
tomato and prune peels are loosened and easily removed.
LIQUID FOOD
 A recent studies on orange juice by treatment with PEF of
100-120 kJ/kg results in 5 log reduction of microbes.
 Thus the shelf life is increased, for untreated juice it is upto
7 to 10 days, for treated one upto 21, 40 or even 60 days
were observed.
SOLID FOOD
 Pre treatment before drying.
 Texture modification because of turgor pressure.
Non food application:
 Application of PEF on hospital waste water to which are
loaded with pathogenic and increasingly with antibiotic
resistant bacteria.

26.  EFFECT ON FOOD NUTRIENTS
Suwandy, et al. reported that PEF does not
induce lipid oxidation of beef.
 Peanut oil was treated by PEF using a square-wave
pulse generated with a pulse duration of 40 μs and pulse
frequency (f) of 1008 Hz.
 This technology could restrain the rate of the lipid
oxidation reaction thus extending the shelf-life of lipid
rich products.
Zhao, W. has been reviewed that PEF has
less impact on the food proteins than thermal
technologies.

27. INFLUENCE OF HIGH VOLAGE PULSE ON MICROORGANISM
E=Electric field strength
Ecrit = Critical electric field
strength.

28.  Hulsheger et al., reported that the larger cells are more
susceptible to electrical field than the smaller cells.
 Were the larger cell (saccharomyces cerevisiae) requires
electric field as low as 2-4 kV/cm, the smaller cell (Listeria
innocua) require electric field of 15 kv/cm as minimum.
 PEF effect on microorganism.
◦Yeast>Fungus>Bacteria>Spores
 Increasing the electric field strength was reported to lead to
a further increase in treatment efficiency

29.  Usha R. Pothakamury research demonstrated the
inactivation of E.coli and Staphylococcus aureus in food.
 By applied electric field of 16kV the E.coli was inactivated
upto nearly 4 log cycles.
 S. aureus inactivated at the range of 12, 14, and 16kV.
PEF RESISTANT BACTERIA:
 The four gram positive bacteria B. subtilis subsp. niger, L.
plantarum, L. monocytogenes and S. aureus. were PEF
treated for 25 kV/cm.
 B. subtilis subsp. niger, L. plantarum and L.monocytogenes
showed a higher PEF resistance at pH 7.0 than at pH 4.0
 S. aureus was the most sensitive bacterial strain at pH 7.0
 L. monocytogenes and L. plantarum were the most PEF
resistant at both pH 7.0 and 4.0

30.  Compared to vegetative cells, microbial spores are more
resistant to high temperature, high and low pH and
mechanical shocks.
 B.subtilis spores inactivated upto 2 log cycles with an
applied electric field of 30kV/cm at 36°C with pulse
duration of 1, 2, 4 and 6μsec.
ENZYME INACTIVATION
 The enzyme inaction by PEF requires stronger electrical
condition than microbial inactivation because some
enzymes are useful for industry.
 Thus PEF allow the destruction of microorganism while
maintaining the activity of some enzymes.

31. The commercial scale PEF pulse
generator with production scale of
 1000 – 10,000 liter/hr requires
$500,000 and $1,000,000 U.S
dollars.
 Rs 3,62,99,100 and Rs
7,25,98,600 in Indian rupees.
The expected lifetime of a high-
pulse voltage generator is around
4-5 years with 20 hr/day of
operation.
 lifetime of a high-pulse voltage
generator is around 4-5 years with
20 hr/day of operation

32. Elea PEF systems installed in a commercial processing facility
for French fries.

33. merits
demerits
 Kills vegetative cells.
 Colours, flavours, and
nutrients are
preserved.
 Relatively short
treatment time.
 Increased shelf life.
 no effect on sensory
and quality attributes.
 High initial cost.
 Not suitable for non
homogenous food.
 Foam forming foods
 Food entrapping
bubbles.
 Highly viscous fluids.
 Energy efficiency is
more.

34. REFERENCES:
 Textbook of Emerging technologies for food processing by DA-WEN
SUN.
 Pulsed Electric Field Processing in Food Technology by Yashwant
Kumar* (2015)
Inactivation of E.coli and Staphylococcus aureus in model foods by
pulsed electric field technology by Usha R. Pothakamury,”(1995)
 Industrial scale equipment, patents, and commercial applications by
Stefan Toepfl (Text book chapter).
 Chemical modifications of lipids and proteins by non-thermal food
processing technologies by Juan Perez(2015)
 Pulsed Electric Fields for Food Processing Technology by Maged E.A.
Mohamed and Ayman H. Amer Eissa (2012)
 Pulsed Electric Field Processing of Foods: A review by
S.JEYAMKONDAN (2017)
Bacterial resistance after pulsed electric fields depending on the
treatment medium pH by D. Garcı´a, N. Go´mez, J. Raso, R. Paga´n*(2005)

35. THANK YOU