This document provides information about pulsed electric field (PEF) technology, including: 1. PEF uses short electric pulses to preserve foods while maintaining fresh quality and nutrients. It kills microbes through electroporation without significantly heating the food. 2. The principles of PEF involve applying high-voltage pulses between electrodes to create an electric field that makes microbe cell membranes permeable, causing death. Factors like pulse strength and time affect treatment effectiveness. 3. Studies show PEF effectively kills bacteria, yeasts and molds in orange juice with reductions of 2-6 log, extending its shelf life while retaining quality. It is a promising non-thermal method for food preservation.

1. NHA TRANG UNIVERSITY
PROGRAM: MSc. IN FOOD TECHNOLOGY
COURSE: FS 518, THERMAL PROCESSING OF FOODS
1. MUSIIGE DENIS
2. SONKARLAY KARNU
3. LE THIEN SA
ACADEMIC YEAR: 2018-2019
PULSED ELECTRIC FIELD TECHNOLOGY

2. INTRODUCTION
 The quest for energy conservation by the manufacturers to reduce carbon
footprint of the processes involved in food processing and preservation
and the increasing consumers’ demand for fresh-like quality foods have
given rise to the development of innovative non-thermal food processing
technologies.
 WHY PROCESS FOODS?
Extend shelf life
Maintain sensory properties
Maintain nutritive properties
Ensure safety
Make more convenient.
Economic value

3. Non thermal processing
 Producing fresh like foods by replacing thermal treatments.
 Produces minimally processed food with fresh quality and higher nutritive
value because of color and flavor retention.
Examples-
 ohmic heating
 microwave heating
 high hydrostatic pressure (HHP)
 Ultrasonication
 PULSED ELECTRIC FIELD
FOOD PROCESSING
THERMAL PROCESSING NONTHERMAL PROCESSING

4. What is pulsed electric field?
 Pulsed electric field (PEF) used short electric pulses to
preserve the food.
 Pulsed electric field (PEF) treatment is an innovative and
promising method for non-thermal processing of
foodstuff.
 It is one of the most appealing technology due to-short
treatment time(typically below 1 second).
-reduced heating effect.
-energy lost during heating food is minimized
-for fresh-like characteristics, high sensorial quality and
nutrient content.
 It is suitable for preserving liquid and semi-liquid foods
removing micro-organisms and producing functional
constituents.

5. THE PRINCIPLE OF PEF
 The pulsed electrical currents is delivered to a product placed between a set of
electrodes
 The applied high voltage results in an electric field that causes microbial inactivation.
The electric field may be applied in the form of oscillatory pulses at ambient
temperature by increasing the permeability of microbial cell membrane
 The processing time is calculated by multiplying the number of pulses times the
effective pulse duration.
 Food is capable of transferring electricity because of the presence of several ions,
giving the product in question a certain degree of electrical conductivity.
 when an electrical field is applied, electrical current flows into the liquid food and is
transferred to each point in the liquid because of the charged molecules present
 After the treatment, the food is packaged aseptically and stored under refrigeration.

6. THE PULSED ELECTRIC FIELD SYSTEM
Working
 The equipment consists of a high voltage pulse generator and a treatment chamber with a
suitable fluid handling system and necessary monitoring and controlling devices.
 Food product is placed in the treatment chamber, either in a static or continuous design, where
two electrodes are connected together with a nonconductive material to avoid electrical flow
from one to the other.

7. WORKING PRINCIPLE CONT’D
 Generated high voltage electrical pulses are applied to the electrodes, which then conduct
the high intensity electrical pulse to the product placed between the two electrodes.
 The food product experiences a force per unit charge, the so called electric field, which is
responsible for the irreversible cell membrane breakdown in microorganisms.
 This leads to dielectric breakdown of the microbial cell membranes and to interaction with
the charged molecules of food
 Hence, PEF technology has been suggested for the pasteurization of foods such as juices,
milk, yogurt, soups, and liquid eggs

8. INPUT REQUIREMENT OF PEF
Input
requirements
of PEF
Microbial
inactivation
15 -40 kV/cm
Improvement
of mass
transfer in
plant/animal
cell
0.7 -3.0 kV/cm
In apple juice
22 -34 kV/cm
Sludge
disintegration
10 -20 kv/cm

9. MECHANISM OF MICROBIAL INACTIVATION BY PEF
 Two mechanisms have been proposed for the mode of PEF action on
microbial membrane:
 electroporation and
 electrical breakdown;
 In both cases, a phenomenon starts by electroporation resulting in
electrical breakdown by which the cell wall is perforated and cytoplasm
contents leak out resulting in cell death.
 The electroporation theory suggests that the main effect of an
electric field on microbial cells is to increase the membrane
permeability due to membrane compression and poration, and cell
inactivation results from osmotic imbalance across the cell membrane
(Tsong, 1990).

10. Stages of electroporation in a cell membrane
through osmosis
The red arrows show the field intensity and blue dots are water molecules

11. Factors Affecting Microbial Inactivation in PEF Treatment
Type and Growth Stage of Microorganisms
 The Gram-positive bacteria are more resistant to PEF treatment than Gram
negative ones
 Yeasts are more sensitive to electric fields due to their larger size,
 Sporulated microorganisms are the most difficult ones to inactivate by PEF
treatment
 Cells of Log phase are more sensitive to PEF treatment than the lag and
stationary phase cells.
Processing parameters
 Field intensity: Smaller cells require higher field intensity for inactivation

12. Factors Affecting Microbial Inactivation in PEF Treatment
 Pulse Wave Shape and Polarity: square pulses maintain peak voltage for a
longer time (over 2 µs) which makes them more lethal and energy efficient
than exponentially decaying pulses
 Bipolar pulses are more effective for microbial inactivation than mono polar
pulses
Environmental Parameter
 Treatment temperature- elevated temperature leads to higher lethality rate
 pH: the lower the Ph the higher the synergetic effect of inactivation
 Conductivity & ionic strength: inactivation level increases as conductivity and
ionic strength decrease

13. Factors Affecting Microbial Inactivation in PEF Treatment
 Treatment Time and Total Specific Pulsing Energy Input
 defined as the product of number of pulses by the pulse
width (µs); achieved in PEF by either changing the flow rate
or the pulse frequency while maintaining the pulse width.
t = Np x Nc x Pw
 The number of pulses:
Np = tr x f
 Residence time:
tr = V/F
 Energy input Q into the food for square pulses,
Q = v.I.Pw / V,
 Treatment time and energy input are linearly correlated;
increasing each can result in further microbial or enzymatic
inactivation.
 t = treatment time
 Np = number of pulses,
 Nc = number of treatment
chambers
 Pw = pulse width.
 f = pulse frequency (Hz)
 tr = residence time (s) in
each chamber
 V = volume of each
chamber (mL)
 F = flow rate (mL s-1)
 v =voltage
 I = current

14. PEF impact on Enzymes
 Compared to microorganisms, more intense PEF treatments are required to
inactivate enzymes
 Mild PEF treatments enhances the activity of some enzymes such as fungal
polygalacturonase (Giner and others 2003).
 The mechanism of enzyme inactivation by PEF is due to unfolding,
denaturation, and breakdown of covalent bonds and oxidation-reduction
reactions caused by intense electric fields in the protein structure (Barsotti
et al., 2002).
 Enzymes are stabilized by weak non-covalent forces, such as hydrogen bonds
and hydrophobic interactions, and the application of high electric field pulses
affects the three-dimensional structure of the globular protein in enzyme
(AlP)

15. PEF impact on Enzymes cont’d
 The electrochemical and thermal effects associated with PEF
individually or in synergy result in changes in the structure and
conformation of enzymes, which leads to inactivation
 The application of an external electric field may affect the local
electrostatic fields in proteins and disrupt electrostatic interactions
of peptide chains leading to conformational changes.
 PEF‐induced electrolysis and free radical formation results in
localized pH shifts in watery systems, and oxidation of amino acid
residues important for the activity and stability

16. Mathematical Model for Microbial and Enzymatic Inactivation
 N and No = microbial population before
and after PEF treatment,
 A and Ao = enzymatic activity before and
after PEF treatment
 bE =regression coefficient;
 E = field intensity
 Ec = extrapolated critical value for field
intensity
 Mathematical model defines and quantifies the
effects of processing parameters on treatment
effectiveness as well as determining critical
factors in inactivation kinetics.
 Hülsheger et al. (1981 & 1983) model relates the
microbial survival fraction S with PEF treatment
time
 ln(N/No) or S = -bE(E-Ec)…….(microorganism)
 ln(A/Ao) or S = -bE(E-Ec) …………. (enzyme)
 The model is based on the assumed linear
relationship between the log survival fraction
and field intensity as well as a linear relation
between fraction of survivors and treatment
time.

17. Juice processing
 PEF treatment produces juice of exceptional
sensorial quality, which is safe from a microbial
point of view.
 The shelf life of fresh orange juices is extended
by PEF treatment from a few days to a few
weeks.
 This extension considerably simplifies the
distribution of this kind of juice and results in
less waste of juice that otherwise would have
expired

18. PEF inactivation of microorganisms in Orange Juice
Microorganism Juice
pH
PEF conditions (E, t,
Tmax)a
Log 10
reduction
Reference
Staphylococcus aureus 3.7 40 kV/cm, 150 μs, 56 ◦C 5.5 (Walkling-Ribeiro and others
2009b)
Listeria innocua 3.5 40 kV/cm, 100 μs, 56 ◦C 3.8 (McNamee and others 2010)
Escherichia coli n.d.c 30 kV/cm, 12 μs, 50 ◦C 6.0 (McDonald and others 2000)
Salmonella typhimurium 3.4 22 kV/cm, 59 μs, 45 ◦C 2.05 (Gurtler and others 2010)
yeasts and moldsb 3.85b 25 kV/cm, 280 μs, T not
reported
>3 (Rivas and others 2006)
Saccharomyces
cerevisiae
3.4 12.5 kV/cm, 800 μs, 10 ◦C 5.8 (Molinari and others 2004)
Lactobacillus plantarum 3.4 22 kV/cm, 59 μs, 45 ◦C 2.57 (Gurtler and others 2010)
Lactobacillus lactis 3.4 22 kV/cm, 59 μs, 45 ◦C 4.15 (Gurtler and others 2010)
Lactobacillus
fermentum
3.4 22 kV/cm, 59 μs, 45 ◦C 2.11 (Gurtler and others 2010)
Lactobacillus casei 3.4 22 kV/cm, 59 μs, 45 ◦C 0.43 (Gurtler and others 2010)
Lactobacillus brevis 3.6 25 kV/cm, 150 μs, 32 ◦C 1.4 (Elez-Mart´ınez and others
2005)

19. PEF inactivation of Enzyme (PME) in Orange Juice
Product PEF conditions (E, t, Tmax)a Inactivation Comments Reference
Orange juice 35 kV/cm, 59 μs, 60.1 ◦C 90% Pulse width used was 1.4 μs (Yeom and others 2000b)
Orange juice 25 kV/cm, 250 μs,
approximately 64 ◦C
90% 2-μs pulse width (Yeom and others 2002)
Orange juice 80 kV/cm, 60 μs, 44 ◦C 92.7%
(estimate)
Exponential pulsed of 2 to 3
μs applied in a batch
system
(Hodgins and others 2002)
Orange juice 20 kV/cm, 4000 μs,
approximately 25 ◦C
≤10% Increased PME activity (Van Loey and others
2002)
Orange juice 35 kV/cm, 1500 μs, 37.5 ◦C 78.1% Continuous treatment(4-μs)
rect pulses applied in
bipolar mode. energy input
8.085 MJ/L
(Elez-Mart´ınez and
others 2007)
Grapefruit
juice
20 kV/cm, 25 μs, 59% Continuous treatment (Riener and others 2009)
Orange–
carrot
blend (4:1
v/v)
25 kV/cm, 340μs, 63◦C 81.4% Continuous treatment with
2.5-μs rectangular pulses
applied in bipolar mode
(Rodrigo and others 2003)

20. Advantages of PEF Processing
 It offers high quality foods
 Reduces detrimental changes in sensory and physical properties of foods
 Preserves food’s fresh-like characteristics
 Kills microorganisms while better maintaining original colour, flavour,
texture and nutritional value of the unprocessed foods
 Highly effective for inactivation of microorganisms
 Increases the pressing efficiency
 Enhances juice extraction from food plants
 Intensifies food dehydration and drying
 It has the potential to efficiently and economically improve energy usage

21. Disadvantages
 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.
 PEF treatment has considerable added value for specific product ranges.
 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.

22. conclusion
 PEF processing under conditions suitable to ensure microbial safety and
stability can result in less degradation of vitamin C, carotenoids,
polyphenols, and volatile aroma compounds in juices than conventional
thermal pasteurization (for example, 95 ◦C for 30 s).
 In addition to PEF technology in combination with standard operations
of the food industry, such as mechanical pressing and extraction with
solvent, used to improve the effiency of these processes and to add
value to food products and by-products. Furthermore, it can be a useful
tool for food processing without any quality defects and nutritional
losses.

23. REFERENCES
 http://www.novelq.org
 http://altered-states.net/barry/rife/pulsedelectricflds.htm
 http://www.foodtech-international.com/papers/PulsedElectricField.htm
 http://www.youtube.com/watch?v=uSK-7dqaVLo
 http://www.sciencedirect.com/science/article/pii/S1466856411000701
 http://www.docstoc.com/docs/76279678/Pulsed-Electric-Field-Processing-(PDF)