FOOD TECHNOLOGIES

Pulsed Electric Field Technology

H Jaeger, Nestlé PTC, Singen, Germany, and Technische Universität Berlin, Berlin, Germany
N Meneses, Bühler AG, Uzwil, Switzerland, and Technische Universität Berlin, Berlin, Germany
D Knorr, Technische Universität Berlin, Berlin, Germany
r 2014 Elsevier Inc. All rights reserved.

Glossary strength or temperature distribution in the treatment

Electroporation Pore formation in the membrane of chamber. This requires experimental information as well as
biological cells caused by the application of an external validation.
electric field. Sublethal injury Structural or functional damage
Hurdle concept The concept of applying combined of microbial cells that is repairable under optimum
methods in order to have a series of preservation growing conditions resulting in a recovery of physiological
methods resulting in multitarget effects for microbial fitness.
inactivation. Treatment intensity The term ‘treatment intensity’ of a
Numerical simulation Computational modeling used in PEF treatment may encompass electric field strength level,
pulsed electric field (PEF) process analysis and number of pulses, frequency, treatment time, pulse energy,
optimization, for example, for calculating electric field total specific energy input, and treatment temperature.

Introduction occurring in the composition of a PEF-treated product or (2) a

process-based approach that identifies critical control points
Pulsed electric field (PEF) treatment is a nonthermal alter- using available knowledge on mechanisms and the de-
native to heat pasteurization of liquid products. Other appli- scription of the process.
cations are the disintegration of plant and animal raw This article aims to give an overview of important hazards
materials and also the induction of stress responses in bio- regarding food safety that may occur during a PEF treatment.
logical cells. However, because of considerably higher treat- Underlying phenomena will be discussed and possible
ment intensities applied for PEF food preservation, the control actions to improve the process performance will be
following outline on food safety aspects related to PEF will pointed out.
focus on this application.
According to several studies, the quality of PEF pasteu-
PEF Basic Principles
rized food product is closer to that of the fresh product than
the heat-pasteurized product and the safety of the fresh PEF technology can be used to induce nonthermal permea-
product is enhanced by the inactivation of vegetative patho- bilization of cell membranes. Depending on the treatment
genic microorganisms. Because PEF is a novel technology, intensity (external electric field strength, number, and dur-
special legal requirements have to be fulfilled (e.g., for the ation of the electric pulses) and cell properties (size, shape,
European countries the regulation of the European Commis- orientation, and conductivity), the pore formation may be
sion No. 258/97 on novel foods and novel food ingredients) permanent or temporary.
and safety concerns have to be addressed. The first commercial Treatment consists of the application of very short electric
PEF application was installed in 2005 in the US for fruit juice pulses (1–100 ms) at electric field intensities in the range
preservation. Clearance by the Food and Drug Administration of 0.1–1 kV cm 1 (reversible permeabilization for stress in-
was already available since 1996, indicating the techniques duction in plant cells), 0.5–3 kV cm 1 (irreversible permea-
potential for safe and gentle preservation. However, to make bilization of plant and animal tissues), and 15–40 kV cm 1
further use of this promising technology and to advance for the irreversible permeabilization of microbial cells. These
its industrial implementation, several aspects need to be taken field intensities lead to the formation of a critical transmem-
into account in order to guarantee a satisfying process brane potential (TMP), which is regarded to be the pre-
performance. condition for cell membrane breakdown and electroporation.
To conduct a PEF safety assessment, two main starting The irreversible electroporation results in a loss of turgor,
points are suggested: (1) a product-based approach (substan- the leakage of cytoplasmic content and lysis. Reversible per-
tial equivalence study) answering the question of alterations meabilization leads to the formation of conductive channels

Encyclopedia of Food Safety, Volume 3 doi:10.1016/B978-0-12-378612-8.00260-2 239

240 Food Technologies: Pulsed Electric Field Technology

across the cell membrane but electrically insulating properties Relevant Impact Factors
will recover within seconds. The inactivation of microorgan-
The factors that affect microbial inactivation during PEF
isms in liquid products or changes in the microstructure
treatment are process related such as electric field intensity;
and texture of treated solid raw materials can be expected as
pulse width and shape; treatment time; and temperature; as
a consequence of the irreversible permeabilization of cell
well as microbial factors such as type, shape, size, concen-
membranes.
tration and growth stage of microorganism, and media factors
High-intensity electric pulses can be generated by the
such as pH; antimicrobials and ionic compounds; electrical
switched discharge of a suitable capacitor bank. The charac-
conductivity; and medium ionic strength.
teristics of the discharge circuit determine the shape of the
The microbial inactivation by PEF depends on character-
time-dependent potential in the treatment chamber. Ex-
istics such as type, shape, growth phase, and inoculation
ponential decay pulses represent a complete discharge of the
amount of microorganisms.
capacity. A rectangular shape of the pulse can be produced by
The cells in the logarithmic growth phase are more sensi-
using special switches, capable of interrupting the current at
tive to inactivation by PEF. Inactivation by PEF is therefore
high potentials, or the implementation of a pulse-forming
higher in the logarithmic growth phase than in the stationary
network. If an additional capacitor is used together with a
phase. Principally, the effect of the electric pulses on the cell
parallel switch, bipolar pulses can be obtained. The geometry
membrane is given by the membrane potential theory. This
of the treatment chamber has a considerable effect on the
theory assumes that the electrical potential across the mem-
electric field distribution and on the total resistance and
brane (TMP) depends on the cell size. The cell size has
therewith on the discharge circuit. The treatment chamber
an inverse relationship to the external electric field strength
design needs to be optimized also taking into account a
necessary to induce a specific TMP. It has been demonstrated
homogenous distribution of the electric field strength as well
by several authors that for smaller particles, higher electric
as characteristics of the fluid flow, viscosity, and particle sizes.
field strength is necessary to reach the critical membrane
potential.
Microbial inactivation by PEF also depends on the char-
Microbial Inactivation by PEF acteristics of the microorganism-containing medium or food.
Factors such as the electrical resistance, pH, water activity,
Effect of PEF on Microorganisms viscosity, presence of solid particles, bubbles, or oil droplets
have an impact on the PEF effectiveness.
Till date there has been no clear evidence on underlying
The conductivity of a medium, defined as the ability to
mechanisms at a cellular level but the main effects have been
conduct electric current, is an important variable in PEF
described to be triggered by the electric field, ionic punch-
technology. Treatment chambers with high conductivity foods
through, and dielectric breakdown of the membrane.
have poor resistance and it is necessary to apply higher voltage
The exposure of the biological cell to an intense external
to achieve similar microbiological inactivation that is achieved
electric field leads to an increase of the TMP, which imposes an
when processing low-conductivity foods. To obtain the same
electrocompression of the membrane. When a critical level of
degree of microbiological inactivation in foods with very dif-
the TMP – which depends on the compressibility, permittivity
ferent conductivity, treatment conditions, such as the inter-
and initial thickness of the membrane – is exceeded, an
electrode gap in the treatment chamber, pulse width, and
electrical breakdown of the membrane occurs. The TMP in-
voltage must be adapted.
duced by an external electric field depends on the intensity of
The influence of pH on the microbial inactivation during
the external electric field and cell size, shape, and composition
PEF treatment plays an important role. Both acidic and
of the membrane. The minimum field strength level of the
alkaline pH values induce additional stress to cells, and con-
external electric field that is required to increase the TMP and
sequently increases their susceptibility to physical and chem-
cause pore formation is defined as critical electric field
ical treatments. The pH can be modified and alters the
strength Ecrit, which depends on the before-mentioned cell
inactivation kinetics by PEF. Depending on the type of
and membrane characteristics. Hence, electric field conditions
microorganism and strain how pH affects the microbial
in the treatment chamber, especially consideration of the
resistance against PEF has also been shown.
nonuniform distribution in most cases, needs to take into
account the existence of such threshold values.
Effective inactivation for most of the spoilage and patho-
Sublethal Injury and Hurdle Concept
genic microorganisms has been shown and colony count re-
ductions depending on treatment intensity, product properties To obtain maximum food safety, a direct transfer of cells from
and type of microorganism in the range of 4–6 log cycles are the vital to the lethal fraction during microbial inactivation is
comparable to traditional thermal pasteurization. favorable. However, because the impact on food quality
Most studies conducted in the past showed that PEF is only characteristics limits the applicable treatment intensities, a
effective against vegetative microorganisms, yeasts, and molds limited number of dead cells may result. Membrane damage
as well as mold ascospores but ineffective against bacterial and inactivation of microorganisms due to PEF was first
endospores and viruses. Recent investigation indicated in- considered as an all-or-nothing event, but a differentiated
creased inactivation of B. subtilis endospores when thermal approach is required even if the critical parameters for the
treatment (75–115 1C) was combined with PEF application electrical breakdown of cell membranes are exceeded. Mem-
(15 kV cm 1, 60–120 kJ kg 1). brane damage and sublethal injury was found to be repairable
 Food Technologies: Pulsed Electric Field Technology 241

under certain conditions and the extent to which cells repair Inactivation in complex media like an orange juice–milk-
their injuries was reported to depend on the treatment in- based beverage was also under investigation. The authors
tensity, microorganism, and treatment medium pH. On the concluded the need for further investigation on the effective-
one hand, sublethally injured cell fractions are a risk from a ness and mechanism of action of the complex food com-
food quality and safety point of view because these cells position during PEF treatment, as the inactivation results
may recover and regain their initial vitality. On the other obtained in the complex orange juice–milk based beverage
hand, sublethally injured fractions have a potential for sub- were lower than in simpler substrates.
sequent complete inactivation by the application of additional In addition to the protective effect of food constituents,
hurdles such as suboptimal storage conditions or the other food matrix properties such as electrical conductivity, heat
inactivation methods such as the application of antimicrobials capacity, and viscosity have to be considered. These parameters
or other food preservation technologies. affect the power requirements necessary for the generation of a
The microbial inactivation rates differ considerably be- desired electric field level as well as the power consumption
tween simple media and a complex matrix. This was partly during operation. Viscosity will determine the flow behavior
attributed to the protective effect of some food compounds and residence time distribution in the treatment chamber
such as xanthan, proteins, or fat. Other studies did neither resulting in treatment time variations and subsequently also in
reveal differences in the microbial inactivation conducted in a nonuniform temperature increase with the occurrence of
either buffer or complex media, nor detect the occurrence of hot spots.
sublethally injured cells after PEF treatment of complex food
systems. However, inactivation kinetics obtained from PEF
treatment in buffer systems have only limited comparability Shelf Life Studies
with real food products. In addition, model microorganisms
An effective microbial inactivation (5 log10) must not only be
used in most studies and the method of sample preparation
accompanied by a minimal impact on food nutrients and
differ significantly from the native state of microbial popu-
vitamins but also by a shelf stable quality. The shelf life of a
lation present in the real food system. The diverse and
product is defined as the period in which the product is still
heterogenous microbial flora present in real foods is not
acceptable for human consumption. Products are spoiled by
comparable to inoculated microorganisms in most cases due
microbial, chemical, and physical processes. The shelf life is
to the strong variability of microbial species and physiological
determined by the raw material quality, product formulation,
state of microorganisms. Consideration of the microbial
processing, packaging, and storage conditions. Numerous re-
growth state, adaptation to treatment media, and existence
searchers have studied the shelf life of a food product in terms
of inhomogenous microbial populations with less sensitive
of microbial spoilage.
subpopulations seem to be the most challenging aspects when
Combinations of kinetic models which determine and
transferring inactivation results to real products and industrial
predict the shelf life of a product after microbial or enzyme
implementation. Assured food safety and stability, along with
inactivation are described. The basis is an inactivation of up to
a desired level of microbial inactivation requires an accurately
5 log10 units of vegetative pathogenic microorganisms. The
defined treatment intensity followed by a predictable mi-
pathogenic Salmonella, E. coli, and Listeria monocytogenes spe-
crobial inactivation. The transfer of inactivation results from
cies can be considered as most important targets for in-
model systems to real foods and the determination of ap-
activation due to its higher resistance to PEF treatments. In
propriate PEF treatment parameters require the consideration
products with low pH values, spore-forming bacteria (Bacillus
of existing particularities.
species) are not able to grow. This means that a pasteurization
treatment is sufficient to achieve a microbiologically shelf
stable product. In case the product is recontaminated, for ex-
Protective Effects of Food Constituents ample, during packaging after treatment, mainly yeasts and
lactic acid bacteria will be introduced in the product. Because
The impact of food constituents on PEF effectiveness is not
lactic acid bacteria are not able to grow in acidic pH foods,
fully elucidated. Some authors report a protective effect of
yeasts are considered to be the target microorganisms during
xanthan, proteins, or fat. Other studies did not reveal differ-
storage. Therefore, a combination of the highest PEF-resistant
ences in the microbial inactivation conducted in buffer or
microorganisms and the microorganism that is most likely
complex media. Investigation of Escherichia coli inactivation
to grow under the storage conditions are suggested for
in an ovalbumin solution, fish egg suspension, dairy cream,
consideration.
and in phosphate buffer did not show any protective effect of
emulsified lipids, soluble proteins, or conductive food par-
ticulate. However, inactivation of Enterobacter sakazakii in
Validation and Availability of Indicators for PEF
peptone water and infant formula milk by PEF at 40 kV cm 1
Performance
for 300 ms was found to cause 2,7 log-cycle and 1,2 log-cycle
reductions, respectively; thus, showing an impact of the Strategies for process validation may include a record of par-
complex composition of infant formula milk in comparison ameters to prove the appropriate performance of a treatment.
to peptone water. When considering PEF effectiveness as a The temperature increase as a result of the dissipation of the
function of the treatment media, the critical field strength and total specific electrical energy input can be used as another
treatment time required was found to be dependent not only measure in order to evaluate the treatment intensity in terms
on cell geometry but also on the properties of the media. of energy input. However, it only reflects an average dose
242 Food Technologies: Pulsed Electric Field Technology

parameter. Measurement possibilities for the process par- contaminated product passes the treatment chamber, to avoid
ameters inside the treatment chamber would be necessary in recontamination of the presanitized processing line. However,
order to detect nonuniformities but they are limited owing to the electric field can only be switched on when the treatment
the small dimension of the treatment chamber and the chamber is filled. Therefore, to avoid insufficiently treated
physical conditions. However, numerical simulation provides product passing the treatment chamber and recontaminating
a capable tool in order to obtain relevant data on inhomo- the line, the installation must be filled with water of similar
geneities of electric field strength, treatment time, and tem- electrical conductivity to start the system at targeted process
perature. Other methods have been proposed to use enzymes parameters.
or chemical indicators to detect thermal or chemical side
effects occurring during PEF treatment. It has to be stated that
sensitivity of microorganisms to PEF is different from their
Electric Field Strength Distribution
sensitivity to thermal treatment. Hence, matrix-specific in-
activation kinetics have to be established in order to define Microbial and media properties have been widely investigated.
product relevant treatment parameters for different target However, the treatment chamber design and its influence
microorganisms. on processing parameters such as the electric field strength
and its distribution have hardly been discussed. One of
the main aspects related to chamber design is the insulator
shape and its impact on the flow and electric field distribution.
Technical Aspects Relevant for Safety Considerations
The insulator and its specific design have a considerable
impact on the process performance as they affect the electric
Treatment Chamber Design
field strength distribution and therefore the microbial in-
The treatment chamber is the key component of the PEF sys- activation. The velocity profile in the treatment chamber
tem for direct application of the electric field in contact with (laminar, transitional, or turbulent) determines the residence
the treatment media. Its design should consider the uni- time distribution and therefore the total treatment time of
formity of the electric field distribution in combination with the product. Because the fluid velocity differs depending
flow characteristics in continuous applications as well as the on the location in the treatment chamber, longer treatment
extent of temperature increase. times will occur near the wall owing to lower flow velocity
Various treatment chamber designs such as parallel plates, and shorter treatment times occur in the center of the treat-
coaxial cylinders, or colinear configurations have been used ment chamber where there is higher flow of velocity. Examples
for PEF processing and some modifications of these basic for modifications as insulator gap/diameter for colinear
designs have been proposed. A comprehensive overview of treatment chambers can be found in literature, where it
different treatment chamber configurations can be found in is stated that a gap increase will provide smaller electric
the further reading list. field strength, but will also provide a more homogenous
Adequate shape of electrodes and the insulator is a pre- distribution.
requisite for an optimal electric field distribution and will The alteration of electric field distribution by modifying
reduce dielectric breakdown effects of the food, because local the insulator geometry can be used to improve the microbial
high electric field strength levels can be avoided, for example, inactivation results. However, this depends strongly on other
by providing a round-edged insulator geometry. Dielectric processing conditions, such as number of pulses, media con-
breakdowns of food are undesired as they cause arcing, which ductivity, and velocity profile, that have to be considered
leads to the destruction of the food, damage on the electrode during the microbial inactivation process. Owing to high
and insulator surface, as well as explosion of the treatment inhomogeneities presented in a continuous treatment system,
chamber due to pressure increase. Electric field homogeneity PEF processing should be characterized in terms of the electric
and the avoidance of low field intensities are not only desir- field strength, treatment time, and specific energy input. An
able from the microbial inactivation point of view but also average value from the previously mentioned parameters with
from the fact that energy dissipation and power consumption their respective standard deviation as well as occurring max-
will take place in low field regions without contributing to the imum and minimum values should be described in detail for
microbial inactivation. the process. The lowest value of electric field strength, treat-
In addition to distribution of the electric field strength ment time, and energy input will be the limiting factors for
and flow velocity considerations, hygienic aspects need food safety reasons and the maximum value for the resulting
to be taken into account for the design and operation of product temperature should be considered with regard to
a PEF unit. product quality. The modification of a colinear treatment
General hygienic guidelines for the food industry (e.g. chamber by inserting static mixing devices provides a possi-
guidelines of the European Hygienic Engineering & Design bility to improve electric field strength distribution, with the
Group, www.ehedg.org) apply and particular attention should aim of increasing the average value and reducing standard
be paid to treatment chamber design and the possibility of deviation. This will result in an increased microbial in-
fouling and accumulation of deposits during processing and activation. The insertion of static mixing devices also provides
their removal during cleaning. Apart from construction a more homogenous velocity profile (thus a more homo-
elements, process aspects and in particular process start up genous treatment time as well) and a more homogenous
with the incoming product after sanitation requires particular temperature distribution, which aims at higher retention of
attention. PEF treatment needs to be started before a heat sensitive compounds.
 Food Technologies: Pulsed Electric Field Technology 243

Thermal Effects and Impact on Safety and Quality fields are unlikely to affect covalent chemical bonds but the
electric field application and related side effects may show an
Although the PEF treatment is a nonthermal food processing
impact on food compounds and process modifications toward
technology, there is a significant temperature increase during
the inactivation of microorganisms and enzyme structures are
high intensity PEF treatment, when applied for pasteurization
also possible. Owing to the application of PEF, changes in the
purposes due to Joule heating. Many authors have described
conformational state of proteins might cause changes in
the temperature distribution in a PEF treatment chamber and
protein structure and enzyme activity.
reported the occurrence of high local temperatures owing to
In general, the mechanisms involved in the inactivation of
inhomogenous field distribution of the electrical field, limited
enzymes and the modification of proteins by PEF are not fully
flow velocity, and recirculation of the liquid. For this purpose,
understood. Possible mechanisms could entail polarization of
numerical simulations using computational fluid dynamics
the protein molecule; dissociation of noncovalently linked
have gained growing interest because experimental measure-
protein subunits involved in quaternary structures; changes in
ment of the related parameters is not possible in most cases
protein conformation so that hydrophobic amino acid or
due to small dimensions of the treatment chamber as well as
sulfhydryl groups are exposed; attraction of polarized struc-
the interference of the measuring device with the product flow
tures by electrostatic forces; and hydrophobic interactions or
and electric field. Apart from the overall liquid temperature
covalent bonds forming aggregates. The effect of PEF on milk
measured at the outlet of the treatment chamber, treatment
proteins may also be explained as a result of the modification
inhomogeneity and the occurrence of temperature peaks
of the apparent charge after exposure to intensive electric fields
within the treatment chamber have to be considered as ther-
and subsequent modification of ionic interactions of the
mal impact factors. This is of particular importance when
proteins. A comprehensive overview of PEF effect on food
discussing PEF effects on functionality of heat sensitive com-
material properties can be found in the literature given below.
pounds, such as proteins or when conducting inactivation
kinetic studies. Additional thermal effects may occur in case of
Electrochemical and Toxicological Aspects
application of high total energy inputs, insufficient tempera-
In addition to the microbial safety and control of process
ture control, or unfavorable treatment chamber design.
parameters relevant for a high level of microbial inactivation,
However, the application of PEF in combination with mild
possible chemical, and toxicological safety issues related to
heat seems to be a promising technique for a gentle, multi-
PEF need to be considered.
hurdle preservation process. The synergism between tem-
In PEF systems working at electric field intensities are
perature and PEF membrane electroporation can be used to
suitable for pasteurization applications, electrochemical re-
improve the inactivation efficiency. The phospholipid bilayer
actions can occur at the electrode–solution interface. Related
structure of the cell membrane changes from a gel-like to li-
effects could be a partial electrolysis of the solution or the
quid crystalline state when increasing the temperature and
corrosion of the electrode material and an emission of metals
increased membrane fluidity leads to reduced membrane sta-
from the electrodes in the liquid.
bility and facilitates the electroporation of the cell membrane.
However, these unwanted phenomena can be limited
The synergetic effect of temperature during PEF inactivation of
or avoided by suitable selection of electrode materials and
microorganisms can be used to improve the inactivation re-
adaptation of the electrical pulse shape and duration.
sults and/or to reduce the electrical energy costs.
The modification of the electrode material such as the use
of titanium, which is oxidized to water insoluble titanium
dioxide at the electrode surface or the application of innova-
PEF Impact on the Food Matrix
tive materials such as carbon loaded polymers have the po-
Food Constituents Affected by PEF tential to decrease the amount of metal release into the
When PEF treatment of liquid or semisolid raw materials is product.
used for microbial inactivation, the desired effect is primarily However, to control the electrochemical reaction it is
nonthermal pasteurization of the food product considering preferable to eliminate causes rather than eliminating results
the microbial cell as target of the treatment. The modification such as the corrosion of electrode material. Therefore, it is
of other food constituents as well as functional food prop- required to modify the electrical characteristics of the PEF
erties may be considered as an unwanted side effect in most systems in two ways: (1) avoiding direct leak currents by im-
cases. However, potential applications to use the electric field proving the electrical switching components and (2) reducing
effect to modify functional properties of food constituents will low frequency alternating voltages and currents by improving
gain increasing attention. the pulse conditions.
The evaluation of the effect of PEF on food compounds is In properly designed PEF systems working at adequate
complex. Available reports are limited and different experi- processing conditions, the metal release can be reduced far
mental setups and processing parameters make them difficult below the existing standards for maximum concentrations in
to compare. The consideration of electric field side effects such drinking water or fruit juices.
as temperature increase and temperature hot spots due to Comprehensive studies on the impact of PEFs on food
Joule heating effects within a nonuniform electric field and the constituents are limited. Most studies focus on single com-
occurrence of electrochemical reactions and pH shifts is the pounds such as enzymes or vitamins. However, to conduct a
most challenging aspect within this context. The nonthermal product specific substantial equivalence study, a complex
inactivation of microorganisms by PEF is based on the elec- analytical approach has to be undertaken which also includes
troporation of membrane structures. High-intensity electric the formation of process induced contaminants. A statement
244 Food Technologies: Pulsed Electric Field Technology

of the Senate Commission on Food Safety of the German Further Reading

Research Foundation on the treatment of food using a PEF is
available since 2008 indicating the need for a case-by-case Barbosa-Cánovas GV, Góngora-Nieto MM, Pothakamury UR, and Swanson BG (1999)
evaluation of PEF-treated products and for the availability Preservation of Foods with Pulsed Electric Fields. San Diego: Academic Press.
Barsotti L, Merle P, and Cheftel J (1999) Food processing by pulsed electric fields:
of standardized process parameters and assessment criteria 1. Physical effects. Food Reviews International 15(2): 163–180.
including indicators. Bhandari B and Roos Y (eds.) (2012) Food Materials Science and Engineering.
Oxford: Wiley-Blackwell.
Gerlach D, Alleborn N, Baars A, Delgado A, Moritz J, and Knorr D (2008)
Numerical simulations of pulsed electric fields for food preservation: A review.
Summary Innovative Food Science and Emerging Technologies 9: 408–417.
Grahl T and Märkl H (1996) Killing of microorganisms by pulsed electric fields.
PEF technology was shown to effectively inactivate micro- Applied Microbiology and Biotechnology 45: 148–157.
organisms in liquid foods resulting in shelf stable safe prod- Huang K and Wang J (2009) Designs of pulsed electric fields treatment chambers
ucts. Because the PEF resistance of microorganisms is different for liquid foods pasteurization process: A review. Journal of Food Engineering
95: 227–239.
compared to thermal treatment and strongly depends on Knoerzer K, Juliano P, Roupas P, and Versteeg C (eds.) (2011) Innovative Food
matrix properties, inactivation levels between microorganisms Processing Technologies: Advances in Multiphysics Simulation. Oxford: Wiley-
and products differ significantly. In addition, technical PEF Blackwell.
treatment parameters with impact on microbial inactivation Knorr D, Engel K-H, Vogel R, Kochte-Clemens B, and Eisenbrand G (2008)
Statement on the treatment of food using a pulsed electric field. Molecular
are multifaceted and provide various adjustment options.
Nutrition and Food Research 52: 1539–1542.
Nonuniform distribution of these parameters in continuous Knorr D, Froehling A, Jaeger H, Reineke K, Schlueter O, and Schoessler K (2011)
industrial scale PEF units and occurring thermal effects result Emerging technologies in food processing. Annual Review of Food Science and
in complex process–product interactions. Hence, the design of Technology 2: 203–235.
a PEF process requires the consideration of process and Lelieveld HLM, Notermans S, and de Haan SWH (eds.) (2007) Food Preservation
by Pulsed Electric Fields. Abington, UK: Woodhead Publishing.
product related characteristics to guarantee food safety. To Raso J and Heinz V (2007) Pulsed Electric Fields Technology for the Food Industry.
have maximum process performance, process optimization New York: Springer.
needs to consider particularities regarding the microbial in- Rubinsky B (ed.) (2010) Irreversible Electroporation. Heidelberg: Springer.
activation such as the occurrence of sublethally injured cells as Van Loey A, Verachtert B, and Hendrickx M (2002) Effects of high electric field
pulses on enzymes. Trends in Food Science and Technology 12: 94–102.
well as the protective effect of a complex food matrix. In
addition, process analytical tools such as numerical simu-
lation are required to exactly define process conditions.
Relevant Websites
Technological aspects such as pulse characteristics, electrode
material, and treatment chamber design can be considered as
http://www.fda.gov/food/scienceresearch/researchareas/safepracticesforfoodprocesses/
key aspects to improve process performance. ucm101662.htm
Food and Drug Administration: Kinetics of Microbial Inactivation for Alternative
Food Processing Technologies.
http://www.foodsafetymagazine.com/article.aspid=3533&sub=sub1
See also: Characteristics of Foodborne Hazard and Diseases: Food Safety Magazine: Process Control of Novel Processing Technologies.
Sublethally Injured and Viable but Nonculturable Cells. Foodborne http://ohioline.osu.edu/fse-fact/0002.html
Diseases: Overview of Emerging Food Technologies. Risk Analysis: Ohio State University: PEF Fact Sheet for Food Processors.
Risk Communication: Novel Foods and Novel Technologies http://www.oardc.ohio-state.edu/sastry/USDA_project.htm
Ohio State University: Safety of Foods Processed Using Alternative Technologies.