Tecnologias energentes en pulsos de luz. una revisión

1. Pulsed Light Treatments for Food
Preservation. A Review
Gemma Oms-Oliu; Olga Martín-Belloso and
Robert Soliva-Fortuny
Horacio Fraguela Meissimilly
Estudiante de Doctorado de Ingeniería de
los alimentos

2. Abstract
Pulsed light (PL) is an
emerging nonthermal
technology for
decontamination of food
surfaces and food packages,
consisting of short time
high-peak pulses of broad-
spectrum white light.
This review of the
principles,
mechanisms of
microbial
inactivation, and
applications of PL
treatments on
foods.
In addition, the critical
parameters of the process
that are needed to optimize
the efficiency of the
treatments and potentiate
their implementation in the
food industry are discussed.
Technological advantages
and disadvantages in PL
(overheating, better
penetration and homogeneity
of the treatment).

3. Description of PL
PL involves the use of intense pulses
of short duration and a broad
spectrum to ensure microbial
inactivation on the surface of either
foods or packaging materials.
Conveyor belt with turning
system
Treated product
Switch
Condenser Lamps
1 and 20 flashes / s
0.01 a 50 J cm −2

4. Microbial Inactivation by PL
Microorganism Pulse energy
(J/cm
-2
)
Treatment
time (μs)
Log reductions
(UFC mL -1)
Reference
Spoilage bacteria
Escherichia coli 3 512 6.82 MacGregor et al. (1997)
Listeria monocytogenes 7 1,500 2.8 Gómez-López et al. (2005a)
Salmonella enteritidis 3 20 5.6 Rowan et al. (1999)
Yeasts
saccharomyces cerevisiae 3 20 4.9 Rowan y col. ( 1999 )
Rhodotorula mucilaginosa 7 1,500 >2.8 Gómez-López et al. (2005a)
Candida lambica 7 1,500 2.8 Gómez-López et al. (2005a)
Fungal spores
Aspergillus flavus 7 1,500 2.2 Gómez-López et al. (2005a)
Aspergillus niger 1 1,000 4.8 Wekhof et al. (2001)
Fusarium culmorum 3 85 4.5 Anderson et al. (2000)
Molds
Algae
Bacteria
Virus
Protozoa

5. Effects of PL on microorganisms
The cell disruption to a
photothermal effect caused by
absorption of UV light when
fluence, energy received by the
sample, is excessive.
Protein elution from cells
irradiated with PL is greater than
that observed under continuous
UV irradiation, when the fluence
was increased.
An expansion of the vacuole and distortion of
the cell membrane exposed to PL is observed.
Therefore, microbial inactivation by PL is
mainly due to structural changes in DNA,
disintegrating them. cellular components
Overheating can cause vaporization and generate a small
vapor flow that causes destruction of the membrane.

6. Process Critical Factors
• The number of pulses.
• Distance from the source of light.
• Thickness of the product are critical
Critical
parameters
These factors will
maximize effectiveness
against microorganisms
and minimize product
spoilage.
Thickness,
cracks or
irregularities
in a product
can decrease
the efficiency
of PL
The composition of
the product can
absorb the effective
wavelengths and
decrease the
effectiveness PL
The PL is affected by the
distance between the
light source and the
sample. The greater the
distance between the
sample and the lamp,
the lower the lethality of
the process
If the intensity of the
light or the duration
of the treatment is
relatively high, the
temperature of the
product increases,
causing the burning of
the surface layers of
the food.

7. Effects of PL on Food Products
Microorganism Food product and
food contact
materials
Pulse
energy
(J/cm
-2
)
Number
pulses
Pulse width
(ns, μs )
Log reductions
(UFC mL -1)
Reference
Liquids
Staphylococcus aureus Milk 1.27 16 – 7.2 Krishnamurthy et al. (2007)
Plant foods
Escherichia coli Blueberries 32.4 180 – 4.9 Bialka and Demirci (2007)
Mesophilic aerobic
microorganisms
Shredded spinach 7 2700 30 μs 0,9 Gómez-López et al. ( 2005a)
Monilia fructigena Strawberries 7 3.750 30 μs 4 Marquenie y col. ( 2003a)
Other foods
Listeria monocytogenes Salmon fillets 5.6 135 – 0.72–0.8 Ozer and Demirci (2006)
Packaging material
Cladosporium herbarum Paper-polyethylene
packaging material
0.977 30 – 2.7 Turtoi and Nicolau (2007)

8. Potential Applications of PL Technology and
Main Limitations
In foods that require rapid disinfection.
In foods called "natural" for not having
the use of residual compounds,
disinfectants and chemical
preservatives.
In foods with smooth surfaces, for the
effective elimination of
microorganisms.
It applies to:
Main Limitations
:
Its limited effectiveness in
controlling food heating.
Limited efficiency of PL due to
shadowing effect in food products.
It is not suitable for cereals, grains
and spices due to its opaque
nature.

9. Conclusions
 PL is a novel nonthermal technology to inactivate
pathogenic and spoilage microorganisms on foods.
 The significant microbial reductions in very short treatment times, the
limited energy cost of PL, the lack of residual compounds, and its great
flexibility are some of the major benefits of the technique.
 There is a need for optimizing the critical process factors to achieve the target
inactivation level for specific food applications without affecting quality.
 Further studies need to be conducted to assess the effects of
PL treatments on food properties beyond safety and spoilage.

10. Thank you for your time