Its about use of pulse electric field to preserve food material.

1. Pulse Electric Fields For Food Processing
Technology
Department of Agricultural & Food Engineering
IIT Kharagpur
Barun Kumar Yadav
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2. Introduction
• High voltages (≤ 100 kV ) in short ( 1-10 µs )
pulses ( up to 1000 Hz ) .
• Total Treatment time < 1 s (generally).
• Product expose to electric fields via electrodes.
• Effects includes permeabilisation of membranes.
• Classes as a “non –thermal” treatment.
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3. History of PEF (Scientific publication)
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4. Scientific publication vs other technologies
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5. Publication vs uptake of HPP
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6. Principle of Technology
• PEF processing for food preservation implies applying
short electric pulses.
• Usually 1±20 µs, but with a range of 50 ns to several
milliseconds.
• With a high field strength (15±80 kV/cm ) .
• Samples placed between two electrodes in a batch or
continuous treatment chamber.
• To generate such a fast electrical discharge, pulse-
forming networks (PFN) are used.
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7. The main components of a PFN
• Power supply: A high voltage generator which supplies
electrical energy at the selected voltage .
• One or several capacitor banks, inductors or/and resistors.
• One or several switch which deliver electrical energy to the
electrodes and the food sample.
• One (or several) treatment chamber(s) with two electrodes
between which the food sample either flows or is encased.
• An oscilloscope to measure voltage across the electrodes and
display pulse shape.
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8. Working
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9. Type of pulse wave form: PEF may be applied in the form of
exponential decaying, Square , bipolar or oscillating pulses.
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10. Mechanism of Microbial inactivation
• There are mainly two type of mechanism :
Electrical Breakdown
Electroporation
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11. Electrical breakdown
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12. Electroporation
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13. • Microbial inactivation increases with an increase in the
electric field strength.
• Gram-positive are more resistant to PEF than those that
are Gram-negative.
• Yeasts are more sensitive to electric fields than bacteria
due to their larger size.
• At low electric fields they seem to be more resistant than
Gram-negative cells.
• Spores are high resistant to PEF .
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14. Input requirement
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Input
requirements
of PEF
Microbial
inactivation
15-40kV/cm
Improvement of
mass transfer in
plant/animal cell
0.7-3.0kV/cm
In apple juice
22-34kV/cm
Sludge
disintegration
10-20kv/cm

15. PEF Critical Factors
Process
- Electric field intensity
- Pulse Width
- Treatment time and temperature
- Pulse wave shapes and polarity
Microbial entity
- type, concentration, and growth stage of microorganism.
Treatment media
- pH, antimicrobials, and ionic compounds, conductivity, and medium
ionic strength.
- Food with large electrical conductivities generate smaller peak electric
fields across the treatment chamber and therefore are not feasible for
PEF treatment.
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16. Comparison between technique ( Cost VS Technique )
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17. Advantage
• Less treatment time and low treatment temperature.
• Substitute for conventional heat pasteurization.
• Increase shelf life and maintain food safety.
• Minimally processed foods of fresh quality, which have
higher nutritional value because of color and flavor
retention.
• PEF inactivates vegetative micro-organisms including
yeasts, spoilage micro-organisms and pathogens.
• Reduction in microorganisms: 4-6 log
• It can be used to pasteurize fluids such as juices, milk and
soups without using additives.
• It increase the juice and oil extraction yeald.
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18. Disadvantage
• High capital cost.
• PEF treatment is effective for the inactivation of vegetative
bacteria only.
• Micro-organisms are destroyed by PEF but spores, with their
tough protective coats, and dehydrated cells are able to survive.
• Refrigeration is required to extend shelf-life.
• Treatment does not inactivate enzymes.
• PEF is a continuous processing method, which is not suitable for
solid food products that are not pump able.
• PEF processing is restricted to food products with no air bubbles
and with low electrical conductivity.
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19. Aspects to be considered in PEF
• Generation of high electric field intensities.
• Design of chamber that impart uniform treatment to foods.
• Minimum increase in temperature.
• Design of electrodes that minimize the effect of
electrolysis.
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20. Application of PEF Technology
Juice processing:
• Applying PEF to cellular tissue an increase in mass
transfer coefficients due to cell membrane
permeabilisation.
• There is 10-12% increase of juice yield when applying
electroplasmolysis to apple tissue.
• Application of PEF for juice processing provides a
potential to replace or enhance conventional cell
disintegration techniques.
• The shelf life of fresh orange juices is extended by PEF
treatment from a few days to a few weeks.
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21. Sugar Processing
• In Conventional procedures for production of sugar from
beets, disintegration and destruction of cell membranes a
thermal treatment at temperatures in the range from 70 to
78°C is applied.
• The membrane de-naturation results in an acceleration of
sugar release into the extraction media, but also cell wall
components such as pectin may become soluble and can
diminish juice purity and quality.
• A PEF treatment of sugar beets could increase mass
transfer rates and could allow to reduce extraction
temperatures and better quality of sugar can be obtained.
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22. PEF treatment of microalgae, seaweed,
and other aquatic species
• Different varieties of macro- and microalgae are sources
of vitamins, pigments, proteins as well as antixodative and
bioactive substances.
• Algae extracts applying PEF treatment could provide a
potential toward a gentler downstream processing.
• There is an increasing in the yield after PEF treatment,
mainly in the case of extractability of growth hormones.
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23. Plant Oil Extraction
 Sitzmann and Munch (1988) reported an enhanced
separation of tankage emulsions when extracting protein
and fat from animal tissue.
 A similar effect can be expected after PEF treatment of
oil seeds prior to recovery.
 Yield and quality of oils has been studied and high oil
yield was developed.
 Oil recovery from olives was improved by 7.4% after a
PEF treatment at 1.3 kV/cm in comparison to the control
sample.
 In soybean oil an increase in iso-flavonoid content was
reported.
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24. Meat & Fish Treatment
• Disintegration of animal cellular tissue is used to enhance
the curing of fish or meat products.
• In case of raw ham a long-term curing and air drying is
applied. During such procedures a PEF treatment can be
applied to improve mass transfer processes and to
accelerate curing, reducing the time requirements.
• An increase in mass transfer rates, resulting in faster
water transport to the product surface and therefore
drying time can be reduced.
• This will lead to drastic saving of energy and better
utilization of production capacities during convective air
drying.
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25. References:
• Food preservation Techniques – Peter Zeuthen and Leif Bagh,
Sarensen, CRC , Woodhead Publ. Ltd.
• Maged E.A. Mohamed and Ayman H. Amer Eissa (2012). Pulsed
Electric Fields for Food Processing Technology, Structure and
Function of Food Engineering, Prof. Ayman Amer Eissa (Ed.), ISBN:
978-953-51-0695-1, Intec, DOI: 10.5772/48678.
• Pulse electric field Technology for food industries , Fundamentels and
application - Javier Raso and Volker Heinz , Springer publ Ltd.
• http://www.foodtech-international.com/papers/PulsedElectricField.htm
• http://www.fda.gov/Food/FoodScienceResearch/SafePracticesforFood
Processes/ucm101662
• http://worldfoodscience.com/cms/index.html@pid=1006021.html
• https://www.youtube.com/watch?v=6LYAPgRyU0c
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