This document provides information on pulsed electric field (PEF) and pulsed visible light processing of foods. PEF uses short electric pulses to preserve foods through electroporation of microbial cell membranes, while minimizing heat production. PEF has been shown to effectively inactivate various microbes in foods like milk, eggs and juices. Pulsed visible light also uses intense, brief pulses of light to inactivate microbes in foods photochemically and through localized heating. Both techniques are non-thermal alternatives to traditional food processing that reduce degradation of nutritional and sensory qualities compared to heat treatments.

1. HFN – 600 Master seminar
Non-Thermal processing of food
- Pulsed Electric Field
- Pulsed Visible Light
presented by
Tamilselvan.T
51094

2. Thermal processing of food:
This method helps in processing of food with the help
of thermal energy i.e., Heat.
The basic purpose of thermal processing are
 Used to reduce or destroy microbial activity.
 Used to destroy or inactivate enzyme activity.
 Used to produce physical or chemical changes to make the food
meet a certain quality standard.
Thermal processing is widely used in industries all over the
world.

3. Disadvantages of thermal processing are:
 It gives cooked flavor to food ex: milk
 It also change organoleptic properties of food.
 Alteration in nutritional properties occurs.
Ex: Protein denaturation, Loss of Heat liable
vitamins and some volatile flavors.
 It is also energy expensive one.
Some thermal processing methods are
Ohmic heating , Microwave heating , Infrared heating , Radio
frequency heating , Drying , Extrusion .

4. Non-Thermal processing of food
Also called Alternative thermal processing
This method of processing commonly does not require
any heat for processing although some amount of heat is produced
during processing.
 Non-Thermal processing of food stuffs now become center of
interest for scientists as it has more advantages than thermal
processing.
 NTP has specific applications in terms of type of food processed.
It gives consumers high quality and minimally processed food
products.

5. New Non thermal processing methods are
High pressure processing
Oscillating magnetic field
Electron beam
PULSED ELECTRIC FIELD
PULSED VISIBLE LIGHT
Pulsed X - ray

6. Ultrasonic
Irradiation
Dense phased Carbon di-oxide
High Voltage Arc discharge
Cold Plasma
Ozone

7. Overall advantages of NTP
 Low processing temperature
i.e., the NTP allows processing of foods below temperature
used during thermal pasteurization.
 Low energy utilization
No need of continuous supply of energy.
 Retention of flavors and taste
 Gives consumer a fresh like taste.
 Inactivates enzymes and Micro organisms.
 Safe and environmentally acceptable

8. PULSED ELECTRIC FIELD

9. Pulsed electric field
It is also called High Electric Field Pulses (HELP)
It is the application of very high field strength for
a very short time to foods placed between electrodes.
 It uses short electric field pulses to preserve food.
 It works in intensity of 10-80 kV/cm with duration of micro to
milli seconds.
 Today, about 20 research groups worldwide are working in this
PEF, but still there is no commercial, industrial system available.
(Pulse - A pulse is a single disturbance that moves through a
medium from one point to the next point)

10. History :
 The bactericidal effect of electric current has already been tested
in 19th century (Prochownick and spaeth, 1890).
 In 1920’s a process called ‘Electropure’ was introduced in
Europe and the USA.
In milk pasteurization it is used by passing current
within carbon electrode treatment chamber.
 In 1950’s pulse discharges of high voltage electricity across two
electrodes for microbial inactivation is first investigated.
 In 1967- First non thermal lethal effect of homogeneous PEF on
microbes by Sale and Hamilton.

11.  Early patents by Krupp in Germany for inactivation of vegetative
microorganisms in milk and fruit juices with an electric field
strength up to 30 kV/cm.
 1987 - Pure Pulse Technologies, USA use electric fields and their
effect on fruit juice quality was investigated by Dunn and
Pearlman.
Components needed :
 High voltage power source
 Capacitor bank
 Treatment chamber
 Electrical switch

12. Principle:
It is based on the principle of Electroporation i.e., Membrane
permeabilization.
 The use of an external electric field for a few micro to milli
seconds induces local structural changes and a rapid breakdown of
the cell membrane which is important component on cell.
 After electroporation, the components of surroundings enter into
cell and makes it rupture.
 Cells that undergo PEF can respond to pulses reversibly or
irreversibly.

14. Working:
 The pulses based on type of food is applied through the electrodes to
the food placed in treatment chamber.
 In the two electrodes, one on high voltage and other on ground
potential separated by insulating material.
 To avoid exposure to electrode surface, a glass coil surrounding the
electrode is used.
 There are three types for passing pulses to the food placed in
treatment chamber.
They are Parallel plate, Coaxial, Coplanar.

15. Parallel plate Coaxial Coplanar

16.  Food is capable of transferring electricity because of the presence
of several ions.
 So, when an electric filed is applied, electric current flows into
the liquid food and is transferred to each point in the liquid
because of 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.

17. Parameters
Process parameters
 Field strength
 Pulse length
 Number of pulses
 Start temperature
 End temperature
 Treatment chamber
 Volume
 Gap
 Flow rate
 Residence time
Microbial parameters
 Type of Microorganism
 Medium composition
 Oxygen concentration
 Time of incubation
Product parameters
 Conductivity
 Composition
 Ionic strength
 pH
 Aw

18. The operation are of two types – Flowing and Non-flowing.

19. Food products can be used for PEF
Milk , Yogurt , Liquid whole eggs, Soups, Brines,
Apple sauce, Tomato juice and foods that can withstand electric
fields.

20. Liquid egg E.coli 6
Coaxial chamber ,37°C
,4 µs pulse length, 2.6
V/µm, 0.5 l/min, 100
pulses
Skim milk Listeria innocua 2.5
Continuous flow,
5.0 V/µm,36 °C ,
32 pulses, 2 µs
pulse length,3.5 Hz.
Milk
Listeria
monocytogenes
4
Co- axial , 3.0 V/mm,50
°C ,600 µs treatment
time, pulse length 1.5 µs
,flow rate 7 ml/s,
Food product Microorganism Log
reduction
Process condition
Examples of Microbial Inactivation by PEF

21. Advantages:
 Providing microbiologically safe food.
 Minimal processing of food.
 Enhance extraction of sugars and cellular contents, metabolites
from plant cells.
 It helps in drying plant tissues.
 Enzyme activity modification.
 Can be used synergistically with pre heat method, HPP and with
antimicrobials like Nisin and lysosyme is under investigation.

22.  Useful for processing of semisolid and liquid foods.
 Since PEF kills cells and impairs water retention, it can aid in
filtration methods.
 Can also be used for the extraction of sugars and starches from
root vegetables.
 Continuous processing is possible.
 Applicable for acid foods, as spores will not germinate in acid
foods.

23. Disadvantages:
 It is an Expensive method.
 Still under research and development.
 Availability of commercial units is less.
 The method of inactivation is still theoretical and not clearly
studied.
 Effectively depends on electrical conductivity of food.
 Not useful for solid foods.
 A reduction in electrode lifetime the release of particles and heavy
metals from electrode may cause toxicity.

24.  PEF has limited effects on microbial spores because some MO can
withstand this.
 Not possible to use in products that contain or could form air
bubbles.
 Not possible to use in foods with higher or variable electrical
conductivity .
 PEF is a non-thermal process, there is an increase in temperature
occurs in treatment chamber.

25. Technical issues to be addressed before commercialize PEF :
 Consistent generation of high strength PEF
 Reliable data acquisition systems and measuring devices
 Identification of the critical, maximum and optimum field strength for
microbial degradation, flow rate and dosages.
 Temperature control and minimization of heat production during
processing.
 The potential for gas bubbles and interference from suspended particles
 The design of full scale treatment chamber
 Aseptic packaging system that are compatible with the process

26. Inactivation of Microorganisms after PEF treatment in pH 7, Batch
treatment, Field strength 2.2 V/ µs, pulse length 2 µs.
(Alvarez & Raso , unpublished data)

27. Energy required for cell disintegration with different techniques
for Potato tissue

28. Non thermal Inactivation of Saccharomyces cerevisiae in Apple
Juice Using Pulsed Electric Fields (Swanson B. et.al., 1995)
Aim:
To study the use of High intensity electric fields in a continuous
system for inactivation of Saccharomyces cerevisiae in apple juice.
Methods :
1). To determine microbial inactivation S. cerevisiae at a
concentration of 2 × 106 cfu/mL was inoculated in commercial apple
juice. Selected field intensities were 13,22,35,50 kV/cm , pulses
selected were 2 to 10 with pulse duration of 2.5 µs.
2). For shelf life determination 5 × 103 cfu of S. cerevisiae per
mL were initially inoculated in the commercial apple juice. Field
intensity was 36 kV/cm and 10 pulses and duration of 2.5 µs. In 15 mL
centrifuge tubes incubated at 4 °C or 25 °C (treated and untreated)
( LWT- food science and Technology, Volume 28, 564-568p, 1995)

29. Results:
1). 6D inactivation of inoculated S.cerevisiae was achieved. The
temperature was only 29.6 °C with two 2.5 s pulses at 50kV/ cm.(which
is lesser than heat pasteurization)
2). Untreated 4 °C and 25 °C shows undesirable fermented
flavor within 9 day and 1 day. But for PEF treated apple juice shows
over 3 week shelf life extension at 4 °C and 25 °C storage.

30. Inactivation of Escherichia coli and Staphylococcus aureus in model
foods by pulsed electric field technology (Swanson B et.al., 1995)
Aim: To study the inactivation of E.coli and S.aureus when subjected to
High voltage electric filed pulses.
Materials and methods : The cultures of E.coli and S.aureus inoculated in
( milk filtrate) and exposed to peak electric field strength of 16kV/cm and
60 pulses with pulse width ranging from 200 to 300 µs.
The temperature of cell suspension was kept below lethal
temperature, to demonstrate the inactivation is not due to thermal effects by
pulses but by electroporation.
Results:
The extent of Microbial inactivation increases when applied electric
field strength increases. E.coli was inactivated upto 4 to 5 log cycles and
S.aureus was inactivated upto 3 to 4 log cycles with a field strength of
16kV/cm. (At 82.2 °C - 5 log reduction achieved by thermal means but
organoleptic properties change)
(Food Research International, Vol. 28(2), pp. 167-171, 1995 )

31. PULSED VISIBLE LIGHT

32.  This technology known since 1980’s , and was approved by Food
and Drug Administration (FDA) in 1996.
 Pulsed Light (PL) technology is an alternative to thermal
treatment for killing pathogenic and spoilage microorganisms in
foods, including bacteria, yeasts, molds, and viruses.
 In the food industry, PLT can be applied to sterilize, sanitize or
reduce microbial load in foods, food packaging materials, as well
as surfaces, environments, plants, devices and media (water, air)
involved in food processes.

33. History
 Many different PL devices were developed before 1970 for
different industrial purposes.
 The use of inert-gas flash lamps generating intense and brief
pulses of UV light as a technique of microbial inactivation
definitely started during the late 1970s in Japan.
This technique was patented by Hiramoto (1984) .
 A great increase in R&D of PLT increase when FDA approved the
use of PLT ‘for Production, Processing and Handling of foods’ and
recommended some conditions for such use.

34.  The electromagnetic radiations are emitted and propagated by
means of waves which differ in wavelength, frequency and energy
(E).
 The term light is generally used to mean radiations having
ranging about from 180 to 1100 nm.
It includes ultraviolet rays UV = 180–400 nm, (roughly
subdivided into UVA = 315–400 nm, UVB = 280–315 nm, UVC=
180–280 nm), visible light = 400–700 nm and infrared rays= 700–
1100 nm.

35. FDA about PLT
According to FDA - ‘Food treated with pulsed light shall
receive the minimum treatment reasonably required to accomplish
the intended technical effect’
FDA recommends, ‘The total cumulative treatment shall not
exceed 120 kJ/m2 which is more than sufficient to achieve a high
inactivation of a wide range of microorganisms including bacterial
and fungal spores’.

36. Principle
Photochemical Effect
When the pulsed light falls the DNA of microbial cells, it
absorbs some energy. Such absorbed energy is able to break organic
molecular bonds, causing DNA rearrangement, cleavage and
destruction and inhibit pyrimidine production.
These modifications finally result in mutations, damage to the
genetic information, impairment of replication and gene
transcription and then in the death of the microorganism cells.

37. Photo thermal effect
Most energy of the light pulses that penetrate through a food
product is absorbed by the layers nearest to the surface and dissipated
as heat, causing in such thin layers a certain increase in temperature.
Since microbial cells have a higher absorption of the pulsed light
than that of the surrounding medium (water), this determines a
localized rapid heating of microorganisms.
At very high pulse power values can reach temperatures
sufficient to cause their overheating, rupture and death and the
extremely short pulse duration prevents the microorganism cell surface
from being cooled by the surrounding medium .

38. Working
 Pulsed light technology (PLT) involves the use of inert-gas flash
lamps which converts short-duration and high-power electric pulses,
as those used in PEF technology, into short-duration and high-
power pulses of radiation included in the spectra of UV , Visible,
IR.
 The shorter the duration of each pulse, the higher the pulse power.
 When compared with continuous light radiations, light pulses show
a much higher penetrating capability through the materials

39.  During the pulse, this system delivers a spectrum that is 20,000
times more intense than sunlight at the earths surface.
 It is measured in Jcm-1
 Operating time : 100 – 400 µs.
 No.of pulses – 1- 20/s

40. Energy difference between Continuous light and pulses of different duration

41. Components
1. The power supply
2. A storage capacitor
3. A pulse-forming network
4. The gas discharge flash lamp
5. A trigger signal
The obtained energy is finally delivered to the target by
various systems depending on the different applications.

42. Item Experimentals Results / Remarks
Shrimp
F = 1-2 J/cm2
n = 4-8
1-3 lcr of Listeria,
results in shelf life
extension of 1 week
versus untreated one.
Freshly baked cakes
in clear plastic
container
F = 16 J / cm2
n = 3
Absence of molds in
treated one at storage.
Shelf life extension
of 11 days.
Commercial raw eggs
F = 0.5 J/cm2
n = 8
8 lcr of salmonella
enteritidis.
Inactivation effect
observed on egg
shells and little into
egg pores.
Examples for effect on Food products

43. Dunn et al. (1989) obtained 10 log reductions of Aspergillus
niger spores by 4 pulses of 40 kJ/m2 or 1 pulse of 120 kJ/m2 using
broad spectrum pulsed light (BSPL).
The PLT of two types :
1. Continuous system
2. Batch system both depending on usage.

44. Continuous Pulsed light system

47. Factors commonly affecting :
 Treatment time
 Distance of sample from light source
 Number of lamps
 Volume of sample
 Orientation
 Design of lamps
 Presence of particulate materials.
 Composition of emitting spectrum

48. Advantages
 Uses less energy. (because of xenon-flash lamps)
 No adverse effects on nutrients.
 Can be used as a powerful sterilization agent
 Environmental friendly
 Extends shelf life of food products.
 Does not leave any residue in food.
 Can be used for sterilization of packaging materials and have
been used in other industries than food.
 Does not cause temperature changes in food.

49. Disadvantages
 Applicable only on liquid foods and surface of solid foods.(0.1 mm)
 The fissures and folds in food prevent microorganisms.
It will give a ‘shadow effect’
 Efficiency depends on microbial exposure.
 Food composition also affects decontamination by PLT.
Ex: Part of radiation is affected by proteins and oils, reducing
effective radiation available for microbial inactivation. So, High protein
or oily foods not suitable for PLT.

50.  Food packaging material must be transparent and also must be
chemically stable.
 Due to failure of light to penetrate opaque and irregular surfaces,
there is generally less microbial inactivation with pulsed light,
compared to other technologies.
 Sometimes reflection loss also possible which result in reduced
ability.
 If excess UVC light, which causes undesirable photochemical
damage to foods or food packaging materials.

51. Impact of pulsed light treatments on antioxidant characteristics and quality
attributes of fresh-cut apples. (Karina R et.al., 2016)
Aim: The effect of PL treatments combined with quality stabilizing dip on the
quality and antioxidant property of fresh cut apples were studied.
Methods : Apple wedges were dipped into a solution of 1% w/v N-acetyl cysteine
and 0.5% w/v CaCl2 and flashed with broad-spectrum light with an overall radiant
exposure of 4, 8, 12 and 16 J.cm-2 .General microbial counts, color, firmness,
phenolic compounds and vitamin C contents were evaluated over 15 days at 5 °C.
Conclusion: Pulsed light treatments stand as a feasible alternative for extending the
microbiological shelf life of fresh-cut apples at 5 °C, while maintaining their quality
and antioxidant attributes.
Experimental result suggested that PL promotes antioxidant potential
and also vitamin C levels are also preserved. a treatment of 8 J.cm-2 in combination
with the immersion into a quality-stabilizing solution may be selected to extend the
microbiological shelf life of fresh-cut apples without dramatically affecting their
texture.
(Innovative food science and Emerging technologies,Vol 33,pp 206-215, 2016)

52. Effect of pulsed light treatment on structural and functional properties of
whey protein isolate (Maresca et.al., 2016)
Aim : To study the effects of Pulsed Light (PL) processing at different
fluences (from 4 to 16 J/cm2) on the structure and functional properties of Whey
Protein Isolate (WPI) solution.
Methods : The determination of the free and total sulfhydryl (SH) groups was
used to detect the variation of WPI tertiary and quaternary structure.
Additionally, PL-induced changes in secondary structure were determined by
FT-IR spectroscopy and the differential scanning calorimetry (DSC), and
primary structure by carbonyl content.
Conclusion: This study reveals the potentiality of PLT to induce changes in
conformational and functional properties of WPI.
The exposure to PL led to increase of concentration of SH groups
and formation of carbonyl groups, which suggest modification of WP tertiary
and primary structure. Only small changes to secondary structure occurs.
Solubility and functional properties were significantly improved by applying PL
treatments at fluences in the range from 8 to 12 J/cm2.All results show PL
treatment was able to partially unfold WPI samples.
(Food Research International, volume 87, pp 189-196, 2016)

53. Conclusion
The application of new preservation methods resulting
in a moderate to non-significant effect in food products. Further
research is essential to demonstrate and explain the effect of new
preservation technologies on the shelf life and safety of food
products.

54. References:
1. Sun, D.W. 2005. Emerging technologies for Food processing. Italy,
Elsevier Academic Press. 63-301 p.
2. Wicker, L. 2007. Non-Thermal food processing/preservation
technologies: A review with packaging implications. Packaging
Technology and Science. 20. 275-286p.
3. Heinz, V.; Knorr, D. 2002. Preservation of liquid foods by high
intensity pulsed electric fields-basic concepts of process design.
Trends in Food science and Technology. 12. 103-111p.
4. Singh, I. 2012. Pulsed electric field processing of foods.
International Journal of Farm Sciences. 2(1): 1-16p.
5. Patrick, C. Alvarez, I. 2001. Critical factors determining
inactivation kinetics by pulsed electric field food processing.
Trends in Food science and Technology. 12. 112-121p.
6. Mercado, V. H.; Chang, F. J. 1997. Non-thermal food preservation:
Pulsed electric fields. Trends in Food science and Technology. 8.
151-156p.

55. 7. Aronsson, K.; Borch, E. 2002. Growth of pulsed electric exposed
E.coli in relation to inactivation and environmental factors.
International Journal of Food Microbiology. 93. 1-10p.
8. Debevere, J. et al., 2003. New preservation technologies:
Possibilities and limitations. International Dairy Journal. 14. 273-
285p.
9. Elmnasser, N.; Guillou, S.; Leroi, F. 2007. Pulsed light system as a
novel food decontamination technology: a review.
Can. J. Microbiology. 53. 813-821p.
10. Ragaert, P. et al., 2007. Pulsed light for food decontamination: a
review. Trends in Food Science and Technology. 18. 464-473p.
11. Fortuny, S. R. et.al., 2010. Pulsed light treatment for food
preservation. Food Bioprocess Technology. 3. 13-23p.
12. Abida, J.; Rayees, B.; Masoodi, F. A. 2014. Pulsed light
technology: a novel method for food preservation. International
Food Research Journal. 21(3). 839-848p.