Pulsed Electric Field

2. WHY TO PROCESS FOODS ?
 Extend Shelf Life
 Maintain Sensory properties
 Maintain Nutritive properties
 Ensure Food Safety
 Make more Convenient.
 Economic Value
FOOD PROCESSING
THERMAL
PROCESSING
NON-THERMAL
PROCESSING

3. NON-THERMAL
PROCESSING
THERMAL
PROCESSING
It maintains the color,
flavour & aroma of the food.
It doesn't maintain the
color, flavour & aroma of the
food.
It is able to kill all the
microbes in the food &
spores also.
It is not able to kill all the
spores in the food.
Initial cost is more but
running cost is less.
Initial cost is less but
running cost is more.
Time required is less . Time required is more.

4. NON THERMAL TECHNOLOGY
• Effective at ambient or sub lethal temperatures.
• Minimal use of energy.
• Retention of desired qualities and nutritional parameters.
• Improve shelf life.
• Temperature rise may be expected or even may be desired.
• May be employed for both solid and liquid foods.
• High hydrostatic pressure, Pulsed electric field, ultrasound,
pulsed light, Irradiation, Electron beam, Oscillating magnetic
field, Ozone, Gas, Plasma.

5. PULSED ELECTRIC FIELD (PEF)
PROCESSING
 High intensity pulsed electric field (PEF) processing involves
the application of pulses of high voltage(typically 20-80
kV/cm) to foods placed between 2 electrodes
It is an efficient non-thermal food processing technique using
short, high voltage pulses.
These pulses induce poration of plant, animal and microbial
cells, leading to cell disintegration and microbial inactivation.
PEF is instant, targeted, flexible, energy-efficient and because
heat is minimized, products have a longer shelf life whilst
maintaining better nutritional value than with traditional food
processing techniques.

6. PRINCIPLE
 PEF technology is the application of short pulses of high
electric fields with duration of micro- to milliseconds and
intensity in the order of 20-80 kV/cm.
 The process is based on pulsed electrical currents delivered
to a product placed between a set of electrodes; the distance
between electrodes is termed as the treatment gap of the
PEF chamber.
 The applied high voltage results in an electric field that
causes microbial inactivation.
 This technology kept food below temperatures normally
used in thermal processing.

7. Important Aspects of PEF
 Generation of high electric field intensities
 Design of chamber for uniform treatment to foods
with minimum increasing temperature
 Design of electrodes
 Large field intensities achieved by storing energy in
capacitor bank from a DC power supply

8. WORKING
PEF technology is based on a pulsing power delivered
to the product placed between a set of electrodes
confining the treatment gap of the PEF chamber.
The equipment consists of
 A high voltage pulse/power generator
 Energy storage capacitor
 A treatment chamber with a suitable fluid handling
system
 Discharge switch
 Necessary monitoring and controlling devices.

9. WORKING
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.
This leads to dielectric breakdown of the microbial cell
membranes and to interaction with the charged molecules of
food.

10. 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.
Generally of two types based on Geometry and placement of
electrodes: parallel plate and coaxial.
Figure 1: A parallel plate treatment chamber

11. Figure 2: A coaxial treatment chamber
Ion conductive membrane made by sulfonated
polysterene and acralyc acid copolymer
Electrolyte zone is facilated electrical
conduction between electrode and ion
permeable membrane

12. WORKING

13. AIM OF PEF PROCESSING
 As a result of PEF processing, dramatic increases in yield and
the preservation of pigments, antioxidants and vitamins. PEF
makes healthy products last longer.
 Despite its targeted effect on cell membranes PEF does not
affect vitamins, flavors or proteins. This allows microbial
decontamination of heat sensitive liquids whilst retaining their
sensory qualities and functional value.
 In particular PEF processing can be used to enhance mass
transport processes during extraction, pressing or drying of
fruits and vegetables. Permeabilization of meat tissue can be
utilized to enhance drying, brining and marinating processes.
 Applied on liquids and semi-liquids PEF can achieve a non-
thermal food preservation while maintaining organoleptic and
nutritional product quality and freshness.

14. MICROBIAL
INACTIVATION
 Pulsed Electric Field (PEF) processing or electroporation
works by puncturing the cell membrane.
 The process is targeted, gentle and clean.
 Loss of cell membrane barrier function causes microbial
death.
 Example:- Membrane disruption occurs when the induced
membrane potential exceeds a critical value of 1 V in many
cellular systems, which corresponds to an external electric
field of about 10 kV/cm in the case of E. coli. In case of
killing E. coli and reducing the microbial load of a liquid
you need a minimum threshold value of about 10 kV/cm.
Electroporation is irreversible above a certain threshold.

16. Exposing a biological cell (plant, animal and microbial) to a
high intensity electric field (kV/cm) in form of very short pulses
induces the formation of temporary or permanent pores on the
cell membrane. This phenomenon, named electroporation,
causes the permeabilization of cell membrane i.e. an increase
of its permeability and if the intensity of the treatment is
sufficiently high, cell membrane disintegration occurs.
Microbial inactivation

17.  In a biological cell membrane acts as a insulator shell to
cytoplasm whose EC is 6-8 times greater than that of cell
membrane
 When a cell suspension is exposed to an electrical field, ions
inside the cells move along the field until they are held back
by the membrane
 As a result, free charges accumulate at both membrane
surfaces
 The accumulation of more surface charges increase the
electromechanical stress or transmembrane potential
 Larger cells (induced potential is greater in a larger cell) are
more susceptible to damage than smaller cells
 Osmotic imbalance and osmotic pressure in cytoplasm
 PEF changes the confirmational status of protein and hence
used to inactivate enzymes responsible for oxidation and off-
flavors

18. Critical Process Factor and Their
Influence on Microbial Inactivation
 Electric field strength
 Treatment time
 Treatment temperature
 Pulse wave shape
 Types of microorganisms
 Concentration of microorganisms
 Growth stage of microorganism

19. COMMERCIALLY
AVAILABLE EQUIPMENT
 Pulsemaster has developed industrial scale equipment -
named Conditioner - with treatment capacities up to
5,000 l/h (1320 US gal./h) for microbial inactivation and
up to 50,000 kg/h (110,000 lb/h) for cell disintegration.
 Well proven pulse generators and treatment chambers are
available.
 The equipment is industry ready and in compliance with
all safety regulations.
 Pulsemaster manufactures a range of PEF systems for
science and research organizations, tailored to suit
specific research needs.

20. MORE AVAILABLE PEF UNITS
 Zhang said that Ohio State has designed three PEF units that differ
primarily in their fluid handling capacity.
 The OSU-4, intended for laboratory use, has 1/8-in-diameter tubing (about
3 mm).
 The OSU-5, designed for pilot-plant use, has 1-cmdiameter tubing (10
mm); it is not commercially available, but OSU will build a laboratory unit
for R&D purposes.
 The OSU-6, a 75- kW commercial unit built by , has 1- to 1.2-cm-diameter
tubing and can process orange juice at 500–2,000 L/hr and apple juice at up
to 5,000 L/hr. also offers several additional commercial units, as well as a
smaller R&D unit and commercial-scale systems rated at up to 20,000 L/hr

21. BENEFIT OF REPLACING THERMAL
PREHEATING IN POTATO PROCESSING
BY PEF TREATMENT
Using PEF systems instead of pre heaters has several
advantages for potato processing. PEF treatment improves
cut quality and significantly reduces French fry breakage.
Water and energy consumption are reduced; blanching,
drying and pre-fry times are shortened.
 The treatment can
also reduce frying oil absorption &
fat content up to 50%.

22. WHAT TYPES OF FOODS
CAN BE TREATED ?
 Depending on the aim of application, solid, semi-
liquid and liquid foods can be treated.
 It can be applied to whole fruits, vegetables and
potato tubers, fruit or vegetable pieces and fruit or
vegetable mashes, prior to separation processes.

23. APPLICATIONS OF PEF
Mild preservation of beverages and semi-liquid food
products,
Treatment of potatoes to replace thermal preheating, and
Extraction processes such as extraction of antioxidants,
extraction of oil and protein from algae, extraction of sugar
from sugar beets and extraction of nutrients or fibers from
peels and stems.
Furthermore PEF processing can be applied for the removal
of acrylamide, concentration of protein from potatoes and
enhancement of production processes for cooked ham and
dry sausage.

24.  Processing of apple juice - treated with PEF at 50kV/cm,
10 pulses, pulse width of 2µs, had shelf-life of 28days (21
days)
 Processing of orange juice – 15kV/cm, 5 months shelf-life
at 4ºC, low loss of vit.C and colour
 Processing of raw skim milk – 40kV/cm, 40 pulses, 2 µs
and shelf life of 2 weeks at 4ºC
 Processing of liquid whole egg – 36kV at 4ºC to improve
shelf life
 Processing of green pea soup – 2 steps of 16 pulses at
35kV/cm(55ºC), shelf life is 4 weeks at refrigerated
temperature
APPLICATIONS OF PEF

25. PEF PROCESSED FOODS AND CHANGE IN THEIR
QUALITY ATTRIBUTES OTHER THAN MICROBIAL
Product Process and Quality Attributes
Apple juice, fresh and
reconstituted
Pasteurization. No change in solids concentration, pH
and vitamin C. loss of calcium, magnesium, sodium, and
potassium. No sensory differences between processed
and untreated juices
Commercial cheese sauce,
reconstituted
Preservation. Better flavor and appearance than
comparable products
Green pea soup Cooking. No difference in sensory properties after 4
weeks storage at 4°C
Liquid whole egg Pasteurization. Prevention of coagulation, superior
quality
Orange juice Preservation at pilot scale. Less than 6% flavor loss,
negligible vitamin C, and color change
Orange juice, fresh-
squeezed
Pasteurization. Minimal loss of flavor compounds, color
and vitamin C
Salsa Preservation, bitter flavor and appearance than
comparable products

26. CAN PEF PROCESSING BE
APPLIED TO PRODUCTS
CONTAINING AIR BUBBLES ?
 The dielectric strength of the food matrix has a significant
influence on the applicability of PEF, as a dielectric
breakdown has to be prevented.
 Air bubbles cannot withstand high electric field strengths.
They may be present in sparkling products or be released
due to temperature increase.
 In particular for microbial inactivation, where a higher
electric field strength is required, air has to be removed
from the product.

27. LIMITATIONS
 The system need to be scaled up to commercial system
 Limited application which is restricted to food
products that can withstand high electric fields
 The lack of methods to accurately measure treatment
delivery

28. DISADVANTAGE
Micro-organisms are destroyed by PEF but spores, with
their tough protective coats, and dehydrated cells are able to
survive, which means refrigeration is required to extend
shelf-life. There are gaps in our knowledge about physical
rather than chemical preservation methods using PEF.
Quantitative studies on food pathogens, real (existing or
new) food matrices and the resulting quality of products
(positive and negative) as well as life-cycle analysis (carbon
foot-print) have not been fully addressed, and proper
legislations is still to be put in place.
In general, the shelf life of both PEF-treated and thermally
pasteurized foods is comparable. Like thermally pasteurized
foods PEF-treated products are usually stored refrigerated.

29. COMMERCIALLY AVAILABLE
PEF TREATMENT PRODUCTS
Genesis Juice Corp., Eugene, Ore., is selling PEF-treated
juices and blends in the Portland market, according to
Zhang. The products include apple, strawberry, and other
flavors. The package is glass with a full label and is sold
from a refrigerated case. Genesis is using an OSU-5 running
at about 200 L/hr.

30. RESEARCH NEEDS
 Confirming the mechanisms of microbial and enzyme
inactivation
 Identification of the pathogens of concern most resistance to
PEF
 Identification of surrogate microorganisms for the pathogens
of concern
 Development of validation methods to ensure microbiological
effectiveness
 Studies to optimize and control critical process factors

31.  Development and evaluation of kinetic models that take into
consideration the critical factors influencing inactivation
 Standardization and development of effective methods for
monitoring consistent delivery of a specified treatment
 Treatment chamber design uniformity and processing
capacity
 Identification and application of electrode materials for
longer operation time and lower metal migration
 Process system design, evaluation and cost reduction

32. THE FUTURE OF PEF
 Researchers all over the world still have many possible
project development designs that need to be focused
on the better understanding of this technology.
 The projects must be related to aspects of the PEF
product and process that have not been addressed yet
and are of relevance to implementation at a
commercial level.
 The results obtained up to now are not enough for
complete generalization of different aspects dealing
with the quality, microbiological, and nutritional
characteristics of products as well as their processing
conditions.

33. THE FUTURE OF PEF
 To facilitate the analysis and comparison of
future investigations, as well as fully utilize the
potential of PEF for food processing, researchers
are aware that there are many technical issues
that need to be addressed.

34. CONCLUSION
 The objective of food preservation
technologies used by the food industry is to
control micro-organisms once they are
contaminating foods.
 Food preservation technologies are based on
the prevention of microbial growth or on the
microbial inactivation.
 Pulsed electric field (PEF) is a potential non-
thermal food preservation technique to replace
conventional thermal processing.