Pulsed light technology uses short, high-intensity pulses of broad spectrum light to kill pathogens and microorganisms on foods. It works through both photochemical and photothermal mechanisms to damage nucleic acids and cause cell death. Several factors influence its effectiveness, like the type of microbe, properties of the food, and design of the pulsed light system. Research shows pulsed light can significantly reduce bacteria on foods like produce, meat, dairy, and packaging materials without negatively impacting quality or nutrients. It is a promising non-thermal alternative to conventional food decontamination methods.

1. Pulsed light system as a
novel food
decontamination
technology
K.SIVAKUMARAN
AS2012740

2. Contents
 Principles
 Mechanism
 Microbial inactivation
 Factors affecting the effectiveness of the
treatment
 Application in the food industry
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3.  Pulsed Light (PL) technology is an alternative to
thermal treatment for killing pathogenic and spoilage
microorganisms in foods, including bacteria, yeasts,
molds, and viruses.
 The treatment consists in applying a series of very
short, high power pulses of broad spectrum light
 FDA : emission wave length 200- 1000nm
pulse width not exceeding 2ms
level of treatment not exceding12 J/cm2
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4. Principles
 Inactivation efficacy – intensity (J/cm2), no. Of
pulses delivered
 Has 5 components
1. The power supply
2. A storage capacitor
3. A pulse-forming network
4. The gas discharge flash lamp
5. A trigger signal
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5.  The light produced by the lamp – the
wavelengths in the range of UV, visible and
IR
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Figure 1: Schematic diagram of a pulsed light
treatment system

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Figure 2: Flow chart of a PEF food processing
system with basic component (Maged et al.,
2012)

7.  Short duration + high peak power of pulses
combined with UV leads to destruction of
microbial cells
 Photochemical mechanism – germicidal effect of
UV (100-280nm)
 primary target is nucleic acids (chemical
modifications and DNA cleavage)
 DNA repair system is inactivated
 Incapability to reproduce, mutations, impaired
replication, death
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8.  Photo thermal mechanism:
 Temporary overheating as a result of absorption
of overall UV light from a flash lamp – biocidal
 Bacteria - Water content is vapourized, as a
result membrane distorts
 Rupturing of Aspergillus niger spores at high
temperature
 Increasing temperature – food sterility
 At low doses – protein retains its’ function.
 At high dosage – death due to loss in protein
structure and nucleic acid inactivation
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Figure 4: Inactivation
of Aspergillus
niger spores using full-
spectrum light - (Dunn
1988)
Figure 3: Inactivation
of Aspergillus niger spores
using filtered-spectrum light -
(Dunn and others 1988)

10. Factors affecting the microbial
inactivation
1. Type of micro-organism – resistant strains ,
optical properties of cell,
2. Interaction between light and the substrate or
between light and the microbial cells –
transparent/ coloured food –refraction, opaque
food –reflection, biological tissues, absorption and
scattering
3. The distance from the light source- when the
distance increase absorption and scattering
diminishes, optical penetration depth – short10

11. Microbial inactivation in food
1. Foods of vegetable origin: spinach, lettuce,
cabbage, carrots, green bell pepper were
exposed to 2700 pulses per side at both sides
 Log reductions 0.56 – 2.04 can be observed in
Mesophilic and aerobic microbes
 Difference - due to the resistance of the natural
microbial population affecting each vegetables
 also the presence of protective substances
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12. 2. Food powders and seeds:
 Wheat flour and black pepper flour were exposed
at an energy level of 31.12 Jcm-2 (64 pulses),
 0.7 and 2.93 log reductions for Saccharomyces
cerevisiae
 Difference – colour
3. Dairy products and fruit juices: treatment of 4
Joule/cm2 , the microbial load reductions in apple
and orange juices for Escherichia coli were 4.00
and 2.90 Log-cycle respectively and for Listeria
innocua were 2.98 and 0.93 Log-cycles
 Staphylococcus aureus in milk – temp increase –
fouling effects, milk quality changes
 BLG in milk- difficulty in digestion12

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4. Eggs for surface decontamination:
 Pulsed light 2.1 J/cm2 death of Salmonella cells
on the surface,
 Slight increase in the temperature
 10.5J/cm2 - did not cause penetration of
Salmonella cells to the egg contents from the
shel
 Sensory qualities and functional properties were
not affected
5. Honey – Clostridium sporogens spores treated with
PL at 5.6J/Cm2

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15. 7. cooked meat products
 Shelf-life extension and inactivation of Listeria
monocytogenes
 Pulsed light treatment for decontamination of
chicken from food pathogens - High-power pulsed
light of 1,000 pulses, treatment duration 200
seconds and total ultraviolet light dose 5.4
Joule/cm2 - reduce viability of Salmonella
typhimurium and Listeria monocytogenes
inoculated on the surface of chicken by 2-2.4 log10
(N/N0) colony-forming units (CFU)/ ml
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16. 9. Decontamination of packaging material- Paper-
polyethylene was artificially inoculated with spores
such as Cladosporium herbarum, Aspergillus niger,
Aspergillus repens and Aspergillus cinnamomeus
and then exposed to pulsed light with 0.244 to
0.977 Joule/cm2 . The highest level of inactivation
of 2.7 log reduction.
10. Application on food processing equipment -
decontamination of the stainless steel surface
contacting meat from Listeria monocytogenes and16

17.  Pulsed light field technology in combination with
other non-thermal processing technologies
11. Mitigation of allergen using pulsed ultraviolet
light - treatment of peanut extracts and peanut
butter showed to deactivate Ara h 2, the most
potent allergic protein present in peanut
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18.  Advantages – quality retention (no thermal effects,
intensity lasts for only a second)
 Nutrient content retention
 Pulsed white light system – no adverse effects on the
nutrients
 Disadvantages -
 folds or fissures in the food may protect microbes
 Resistant strains - Listeria monocytogenes
 Applicable - liquid foods and surface of solid foods
 packaging material – chemically stable18

19. Summary
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 Alternative to thermal food processing
 High efficient, higher degree of
microbial inactivation efficiency
 No.of pulses, intensity, depth of
substrate the distance from the PL
source determine the efficiency
 Bacterial inactivation - UV + thermal
effect
 Researches are carried out –
decontamination of foods that are
commonly associated with food
poisoning

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