pulse electric field

1. Presented by
Kulwinder Kaur

2.  The spoilage microorganisms may cause the spoilage of food
product and reduce the quality of the food product.
 Although heating inactivates enzymes and microorganisms, the
organoleptic and nutritional properties of the food suffer by
energy intensive heat treatment.
 Nonthermal processing is helpful in achieving similar or better
food safety and quality at processing temperatures and/or
times.
 HPP, Ultrasound, high irradiation were reported to affect the
structures of proteins and polysaccharides, and resulted into
changes in texture, physical appearance, and functionality of
foods.

3. • A non-thermal method of food preservation
• Application of short pulses (upto 100Hz) of high
electric fields (10-80kV/cm) for short duration ( 1-
10µs) to food between two electrodes
• Treatment time < 1s
• Treatment time = number of
pulses x effective pulse
duration

4. • Bactericidal effect of electric current19th
century
• Lethal effect
• Electropure or ohmic heating (220V)
• Milk pasteurization
1920
• Pulsed high voltage or electro hydraulic
treatments
• High voltage pulses generated across
electrodes were used to create pressure of
upto 250Mpa within pressure vessel
1950
Historical Background

5. Continue…….
• Membrane rupture theory for extraction of
cellular content and transfer of genetic
material across cell membrane
1980-
1990
• Commercialization of first PEF treated
apple cider in USA2005
• PEF treatment line for juice preservation in
Europe2009
• PEF treated vegetable processing line with
capacity 50t/h2010

6. Mechanisms of Microbial activation
They are mainly two types of mechanism.
Electroporation
Electrical Breakdown

7. Electroporation
 Cell exposed to a high voltage electric field temporarily
destabilizes the lipid bilayer and proteins of the cell
membrane.
 Cell becomes permeable and causes eventual rupture of the
cell due to formation of large pores.

8. Electrical Breakdown

9. A Bacillus cereus cell
Before treatment After treatment

10. System components
 POWER SOURCE
 HIGH VOLTAGE PULSE GENERATOR
 TREATMENT CHAMBER
 A SUITABLE PRODUCT HANDLING SYSTEM
 A SET OF MONITORING AND CONTROLLING
DEVICES

12. Pulse forms
Oscillatory pulses Exponential Decay Pulse

14. Treatment chamber
To keep the product during pulsing, and to house the
electrodes, uniformity of process depends on its design
Batch systems
Handling of static volumes of solid or semi-solid foods.
Mostly parallel plate systems
Uniform treatment

15. Continuous system
Medium is pumped at a known flow rate and pulses at a known
pulse frequency.
Two electrodes, a spacer and two lids
Electrode (stainless steel), whereas the spacer and lids (polysulfone)
Parallel plate, coaxial and co-field chambers

16. a) parallel plate, (b) coaxial and (c) co-field configuration.

17. A co-linear chamber consists of a set of hollow,
cylindrical electrodes separated by insulators in
which the product is pumped through the
drilling; the flow is not perturbed by any
impediments. It is found to result in higher
inactivation rates compared to batch systems

18. Product handling
To pass the liquid food through the treatment
chamber
Flow channel between electrode to avoid dead corners
Cooling of chamber by flowing water through jackets
Controlling and Measurement devices
Pressure safety device
voltage, current and temperature measuring device

19. Working of Pulsed Electric Field System

20. Factors affecting PEF processing
Technical
• Field strength
• Treatment time
• Treatment
temperature
• Pulse shape
Biological
• Type of
microorganism
• Size
• Shape
• Species or
growth state
Medium
• pH
• Conductivity
• Composition of
food system

21.  Microbial inactivation of beverages
 Extraction of fruit juice
 Beer production
 Extraction of oil
 Dairy and egg products
 Meat industry
 Sugar production
 Enhancement of drying, cutting and frying of
Potato

22.  Traditional thermal treatments (pasteurization,
sterilization, and ultra‐high temperature)
 Depolymerization of macromolecules in the cell
membrane of microorganisms which leads to their
inactivation
 Prevention of color change of puree and juice if
combined with standard thermal treatment,

23. Juice Processing
Due to cell membrane permeabilization, an increase
in mass transfer coefficients occurs
Jemai et al., noticed that treatment of apple juice
resulted in enhancement of diffusion coefficients
of soluble substances
Disintegration of biological tissues that enhances the
extraction of intracellular compounds from
different fruits like lycopene, carotenoid,
antioxidants etc

24. Alcoholic beverages
Microbial growth control is a crucial treatment step during wine
production and before packaging
Traditional treatments : Addition of sulfur dioxide and the
application of thermal sterilization
PEF treatment:
• Control of microbial growth
• Enhancement of polyphenol
extraction,
• Protects and retains the heat-
sensitive components of alcoholic
beverages

25. Extraction of vegetable oil
Disruption of the cell envelopes of the olive paste that act as
a physical barrier is required to facilitate the oil release
during malaxation.
Crushing, screw press, hydraulic press, solvent extraction are
time and energy consuming.
PEF being cold technology can improve oil yield as well as oil
quality extracting from solid oil contain seeds by the
formation of pores in cell membranes that were not
disrupted by the crusher.

26. Milk Processing
 Thermal processing by Pasteurization
 Refrigeration slows the bacteria metabolism
 PEF processing for microbial reduction in ultra
filtrate and skim milk for E. Coli and Listeria
 Quality of milk depends
upon microbial and
enzymatic activities

27. Egg processing
Being a favorable growth medium for several
microorganisms the pasteurization of liquid egg
products is mandatory to ensure the storability and
food safety.
Combined PEF treatment and storage at low
temperatures enables a shelf life increase without
the addition of preservatives.
The water soluble protein content and mechanical
properties of egg gel got improved

28. Meat & Fish quality
An increase in mass transfer rates, resulting in faster water
transport to the product surface and therefore drying time
can be reduced
This leads to drastic saving of energy and better utilization of
production capacities during convective air drying
Enhancement of cell permeation
to increase tenderness
Attenuation of microbial load to
improve the shelf life

29.  Strong polarization of viable cells by an external electric field
leads to an increase in cell membrane conductance and
permeability.
 Improved extraction of sucrose from sugar beets, higher
product quality and purity,
 Increased process capacity and a significant reduction of the
energy input and the water use.
Strong polarization of viable cells by an external electric field leads to an increase in cell membrane conductance and permeability. By p

30. Potato processing

31. Advantages over other techniques
 Applied for liquid or semi-solid products
 Ambient, sub ambient and slightly above ambient
temperature
 Reduced Temperature as well as time
 Retention of nutritional and organoleptic
properties
 Rapid breakdown of cell membrane
 Prevention of food contamination
 It can be operated in a continuous mode and be
easily integrated into existing processing lines.

32. • High capital cost
• Inactivate yeasts and vegetative bacteria only
• Micro-organisms are destroyed, but not spores
• Refrigeration is required to extend shelf-life
• Difficult to inactivate enzymes
• Not suitable for solid food products that are not pumpable
• Restricted to food products with no air bubbles and with
low electrical conductivity