5. KITTUR RANI CHANNAMMA COLLEGE OF HORTICULTURE,
ARABHAVI
SEMINAR-II
Preservation of juice by pulsed electric
field
ARCHANA T JANAMATTI
UHS13PGM341
PHT DEPARTMENT
6. Basic concept of PEF
• Non thermal food preservation method
• Based on the use of electric fields
• Extend the shelf life of food products
• Preserve quality attributes
• Microbiological safety of the food
Toepfl et al., 2005
7. • It involves the application of high voltage
(typically 20 – 80 kV/ Cm) in short (1-10 µs)
pulses ( up to 1000 HZ) to foods between two
electrodes
• Total treatment time < 1s (generally)
• Conducted at ambient, sub – ambient, or
slightly above ambient temperature
What is pulsed electric field ?
Toepfl et al., 2005
8. The principle of
PEF
ELECTROPHORATION
Exposing a biological cell (plant, animal
and microbial) to a high intensity electric
field (kV/cm) in form of very short
pulses (μs to ms) induces the formation
of temporary or permanent pores on the
cell membrane.
Toepfl et al., 2005
10. How this can be exploited commercially ???
Area 1: Preservation – microbial inactivation
e.g. Preservation of high quality beverages
Area 2 : Cell disintegration – less difficulty vs. Above
e.g. Extraction of juices and ingredients
Dehydration of fruits and vegetables (↑ drying rate)
Toepfl et al., 2005
11. Mile stones of pulsed electric field
1920 1950 1960 1968 1980 1988 2003 2007
ELECTROPURE
ELECTROHYDRAULIC
TREATMENT
DOEVENSPECK-PEF
SALE&HAMILTON–PEFON
MICROBES
GENETRANSFER
PATENTTOKRUP–ELCRACK,
ELSTERIL
CELLPERMIABILIZATION
GENESISJUICEPRODUCTION
20001960
Zhang et al., 2008
20201970
14. The main components of PEF
Pulse generating
system
Treatment chamber
Fluid handling system
Control and
monitoring device
15. PUSLE GENERATION SYSTEM
Generation of DC voltage at the
required intensity by a power
supply
Storage of electrical energy in a capacitor
or of group of capacitors
Release of high voltage in the form of pulse (pulse width
and shape) through pulse forming network
Barbosa et al., 1998
16. Barbosa et al., 1998IMPUSLE GENERATION
SYSTEM
ON ON/ OFF
EXPONENTIAL DECAY
PULSE SQUARE PULSE
19. FACTORS OF THE
PRODUCT
Composition
Factors vs. Microbial
inactivation
Ionic strength
Conductivity
pH
Air bubbles
Solid/ fluid
Fat / carbohydrate
Barbosa et al., 1998
20. Application of PEF
Pasteurization of foods such as juices, milk, yogurt, soups, and liquid eggs
Cause the formation of large, permanent pore in cellular tissues, which can
be used to improve juice yield
Plant oil extraction
Barbosa et al., 1998
21. Application of PEF
Induce increase in mass and heat transfer and enhance drying process
Enhance extraction of sugars and other cellular content from plant cells,
such as sugar beets
For heat-sensitive liquid foods where thermal pasteurization is not an
option (due to flavour, texture, or colour changes), PEF treatment would be
advantageous
Barbosa et al., 1998
24. Objective: To investigate the inactivation of L. brevis suspended in
the orange juice by HIPEF
Treatment details:
Lactobacillus brevis strain – CECT 216
HIPEF:
Continuous flow bench scale system
Square wave pulses
Electric field strength – 5, 15,20,30,35 kV/cm
Treatment time – 50, 150, 300, 600 and 1000 µs
Pulse width – 1, 2, 4, 8 and 10 µs
Frequency – 50, 150, 200, 250 and 300 Hz
Polarity – monopolar and bipolar
Pedro et al., 2005
25. Pedro et al., 2005
Figure 5: Inactivation of L. brevis in orange juice exposed to mono- (A), and bipolar (B) HIPEF
(mean7SD, n ¼ 4). Pulse frequency=200 Hz; pulse width=4 µs. Square pulses. E, electric field
strength. Thermal treatment=90± 1 ⁰C/1 min (horizontal line)
26. Figure 6: Effect of pulse frequency on the survival fraction of L. brevis in orange juice
exposed to HIPEF (mean7SD, n ¼ 4). S, survival fraction; f, pulse frequency. Electric
field strength=30 kV/cm; treatment time=300 µs; polarity mode=bipolar; pulse
width=4 µs. Square pulses. The plotted line corresponds to a linear model fit (Eq. (1)).
R2, determination coefficient; significance level, p ¼ 0:05
Pedro et al., 2005
27. Figure 7: Effect of pulse width on the survival fraction of L. brevis in orange juice exposed
to HIPEF (mean7SD, n ¼ 4). S, survival fraction; t; pulse width. Electric field strength=30
kV/cm; treatment time=300 µs; polarity mode=bipolar; pulse frequency=200 Hz. Square
pulses. The plotted line corresponds to a linear model fit (Eq. (2)). R2, determination
coefficient; significance level, p ¼ 0:05.
Pedro et al., 2005
28. Figure 8: SEMs of untreated and HIPEF-treated cells of L. brevis in orange
juice. (A) Untreated (2.000); (B) treated (2.000) at a field strength of 35
kV/cm for 1000 ms using pulses of 4 µs width at 200 Hz frequency applied in
bipolar mode. Arrows indicate damaged cells or cells with rough surface or
merging cells.
Pedro et al., 2005
29. Figure 9: TEMs of untreated and HIPEF-treated cells of L. brevis in orange
juice. (A) Untreated (20.000); (B) treated (25.000) at a field strength of 35
kV/cm for 1000 µs using pulses of 4 µs width at 200 Hz frequency applied in
bipolar mode. Arrows indicate the ruptured cell wall or cytoplasmatic
material that has leaked out of
the cells.
Pedro et al., 2005
30. Flavour retention and related enzyme
activities during storage of strawberry juices
processed by high-intensity pulsed electric
fields or heat
31. Objective: The aim of the present work was to study and compare the retention
of volatile compounds contributing to the strawberry characteristic aroma during
the commercial shelf-life of HIPEF and thermally-processed strawberry juices. In
addition, this study evaluated the effect of HIPEF and thermal processing on
enzyme activities involved in flavour synthesis.
Treatment setup
HIPEF
35kV /cm for1700 µs
Square wave pulse of 4µs
Pulse frequency of 100 Hz in a bipolar mode
Thermal treatment (TT)- 90 ⁰C for 30 s and 60 s
Ingrid et al., 2009
32. Figure 1: Effects of HIPEF and thermal treatments, 90 ⁰C for
60 s (TT 60 s) or for 30s (TT 30 s) on residual lipoxygenase
(RALOX) activity (mean ± SD) of strawberry juice throughout
storage at 4 ⁰C
Ingrid et al., 2009
33. Figure 2: Effects of HIPEF and thermal treatments, 90 ⁰C for 60 s
(TT 60 s) or for 30 s (TT 30 s) on residual β-glucosidase ( RAβ-LGUC )
activity (mean ± SD) of strawberry juice throughout storage at 4 ⁰C
Ingrid et al., 2009
34. Table 1: Effects of HIPEF treatment and thermal treatments, 90 ⁰C for 60 s (TT 60 s) or for 30 s (TT 30
s) on the retention of hexanal, 1-butanol, linalool and DMHF (mean ± SD) (n = 3) of strawberry juice
throughout storage at 4 ⁰C Ingrid et al., 2009
35. Carotenoid and phenolic profile of tomato
juices processed by high intensity pulsed
electric fields compared with conventional
thermal treatments
36. Objective: The aim of the present work was to evaluate and compare
the effects of HIPEF processing and heat pasteurisation on individual
carotenoids and phenolic compounds of tomato juice
Treatment details:
1. Pulsed electric field treatment
35kV/cm for 1500 µs
Bipolar square wave
Pulse of 4 µs with frequency of 100 Hz
2. Thermal treatment
90 ⁰C for 60 s
90 ⁰C for 30 s
Isabel et al., 2009
37. Table 2: Effects of high-intensity pulsed electric field and heat pasteurisation on carotenoids
of tomato juice throughout storage at 4 ⁰C Isabel et al., 2009
38. Table 3:Effects of high-intensity pulsed electric fields and heat pasteurisation on phenolic
compounds of tomato juice throughout storage at 4⁰C Isabel et al., 2009
39. Thermal and pulsed electric fields pasteurization
of apple juice: Effects on physicochemical
properties and flavour compounds
40. Objective: The aim was to investigate the impact of PEF and HTST
pasteurization of apple juice on retention of volatile compounds
which are responsible for characteristic aroma and tasteful flavour
Treatment details:
Golden delicious apple variety
PEF treatment: 35 kV/ cm for 1200 µs with 4 µs
bipolar pulses
Heat pasteurization: 90 ⁰C for 30 s
Rosas et al., 2007
43. Figure 3: Effect of PEF and HTST treatment method on total phenol
compounds of pasteurized apple juice
Rosas et al., 2007
44. Rosas et al., 2007
Table 4: Percentage of volatiles losses, compared with untreated
sample, in apple juice treated by two methods
45.
46. Objective: The aim of this paper is to evaluate the effect of PEF
processing on the bioactive compounds and browning activity
in comparison with thermally treated Embilica officinalis juice
Vasudha et al., 2013
Thermal treatment : 90 ⁰C for 60 s
Storage : 20 ⁰C for 6 weeks
Rectangular monopolar pulse
Pulse width - 4µs
Electric field strength – 24 k V/ cm
Pulse frequency – 1 Hz
Treatment details:
Pulsed electric field treatment
47. Figure 4: Effects of PEF processing on total polyphenolic content of
Emblica officinalis Juice
Vasudha et al., 2013
48. Vasudha et al., 2013
Figure 4: Effects of PEF on non enzymatic browning index of Emblica
officinalis juice
49. Vasudha et al., 2013
Table 5: Effect of PEF and thermal treatment on formation of 5-hydroxymethyl-2-
furfural and on DPPH
50.
51. Objective: The purpose of this study was to evaluate the microbiological
shelf life of apple, pear, tomato, strawberry and orange juice treated by
HIPEF with or without added citric acid or cinnamon bark oil.
Treatment details:
Apple ( Malus domestica Borkh var. “Fuji”)
Pear ( Pyrus communis L. var. “Flor de invierno”)
Tomato ( Solanum lycopersicum var. “Roma”)
Jonathan et al., 2012
Strawberry (Fragaria spp. var. “Camarosa”)
Orange (Citrus sinensis L. var. “Valencia”)
53. Table 7 : Estimated values of the Gompertz’s parameters of mesophilic, mold and yeast and
psychrophilic populations of HIPEF-treated fruit juices stored at 5 ⁰C
Table 6: Estimated values of the Gompertz’s parameters of mesophilic, mold and yeast, and
psychrophilic populations of untreated fruit juices stored at 5 ⁰C
Jonathan et al., 2012
54. Table 8: Microbiological shelf life of fruit juices under different processing conditions and
stored at 5 ⁰C Jonathan et al., 2012
55. Present status
Today about 25 research groups working in this area world wide
Though the technology has been explored almost 50 years ago,
only a limited amount of technical or industrial scale prototypes
or commercial applications available at present
Manufacturers
Pure pulse technologies, USA
DIL (German institute of food
technology)
The first commercial scale
continuous PEF system is-
The Ohio State University
Department of Food Science and
Technology.
Heinz et al., 2007
57. Cost of technology
US $250,000 to 500,00
The PEF processing would add only $0.02 to $0.07/L to final
food costs.
A commercial-scale PEF system can process between 1,000
and 5,000 litres of liquid foods per hour and this equipment is
scalable.
Heinz et al., 2007
59. Comparision between the PEF and Thermal
Processing
PULSED ELECTRIC FIELD THERMAL PROCESSING
It is maintain the color, flavour &
aroma of the food.
It doesn't maintain the color, flavour
& aroma of the food.
Initial cost is more but running cost
is less.
Initial cost is less but running cost is
more.
Less time required. More time required.
Gauri et al., 2000
60. Plus Less treatment time
Low treatment temperature
Substitute for conventional heat pasteurization
Increase shelf life and maintain food safety with low
processing costs
PEF inactivates vegetative micro-organisms including
yeasts, spoilage micro-organisms and pathogens.
Minus
High capital cost
Effective for the inactivation of vegetative bacteria only
Spores, with their tough protective coats are not destroyed
Refrigeration is required to extend shelf-life
PEF is a continuous processing method, which is not
suitable for solid food products that are not pumpable
PEF processing is restricted to food products with no air
bubbles and with low electrical conductivity
Gauri et al., 2000
64. Many possible project development designs that need to be focused
on the better understanding of this technology
There are many technical issues that need to be addressed
To ensure food safety, a risk assessment is required that deals with
chemical safety of PEF treated products in relation to public health
future
aspects..............................
Based on theoretical considerations and calculations, taking
into account field strength, current, time, polarity and
chemical composition of food products, the FDA
decided that there is no objection to PEF treatment of
food for preservation purposes
65. Conclusion
SL.
NO
JUICE PROCESSING
CONDITION
PURPOSE
1. STRAWBERRY 35 kV/ cm for 1700 µs Retain the volatile compound
and enzyme activities involved
in flavour synthesis
2. TOMATO 35 kV/ cm for 1500 µs Maintain the total carotenoid and
phenolic content of juice
3. APPLE 35 kV/ cm for 1200 µs Reduce volatiles losses and
maintain greater total phenolic
content
4. AONLA(Embelica
officinalis )
24 kV/cm for 500 µs Retain bioactive compounds and
to reduce the browning activity
5. ORANGE 35 kV/ cm for 1000 µs To inactivate lactobacillus brevis
6. APPLE, PEAR
AND TOMATO
35 kV/cm for 1575, 1600,
1000 respectively
To inactivate microbes and to
maintain sensory properties
66. PEF technology offers potential alternatives
to the food industry to accomplish
preservation process with high quality , safe
and nutritious food.
Consumer preferences have shifted towards fresh, healthy, tasty foods, which are readily accessible, easily stored and quickly
prepared. Providing such foods in a form suitable for mass production and distribution, which will store as readily at home as in
the supermarket, without affecting flavour, texture and colour, is technically difficult and expensive. The majority of European food
manufacturers are small companies with few resources and limited expertise to develop and implement new technologies. The
advantages and disadvantages as well as the technical problems and potential risks associated with new technologies are often
more complicated than first imagines. This business case, describing pulsed electric field (PEF), considers some important issues
and serves as a basis for discussion.
Since 2005 the first commercial PEF application has been reported (Clark 2006) for fruit juice
preservation in the US. In a scale of 200 l/h premium quality juices are treated at Genesis,
Eugene, US, a fruit juice cooperative using an OSU system. Genesis used to distribute
unpasteurized, premium fruit juices, but in 2003 a warning letter of FDA was published (FDA
2003), initiating the quest for a non-thermal preservation technique. After a PEF
pasteurization a shelf life of four weeks is obtained, clearance of FDA is available since
1996, indicating the potential of the technique for safe and gentle preservation.
Transforms low electric power from low utility level voltage to pulsed high intensity electric fields
Charged by DC high voltage power supply
Dependent on electrode distance to produce pulses of sufficient electric field strength
Electric power is discharged across high voltage switch and protective resistors within microseconds
Preserve the original sensory and nutritional characteristics of foods due to the very short processing time and low processing temperature
The shelf life of fresh juice is extended by few days to a few weeks
Environmental friendly as no waste is generated
Inactivates microorganisms and inhibit enzymes
PEF inactivates vegetative micro-organisms including yeasts, spoilage micro-organisms and pathogens, and it can be used to
pasteurise fluids such as juices, milk and soups without using additives.
pasteurisation or it can operate at room temperature to retain quality and heat-sensitive vitamins. PEF can be used as continuous
process but, after processing, products have to be packaged hygienically and kept cool during storage.
PEF processing offers high quality fresh-like liquid foods with excellent flavor, nutritional value, and shelf-life. Since it preserves foods without using heat, foods treated this way retain their fresh aroma, taste, and appearance.
Application of PEF technology has been successfully demonstrated for the pasteurization of foods such as juices, milk, yogurt, soups, and liquid eggs.
It is suitable for preserving liquid and semi-liquid foods,
removing micro-organisms and producing functional constituents.
PEF causes the formation of large, permanent pores in cellular tissues, which can be used to improve juice yield, increase
concentrations of functional components and enhance the characteristics of dried produce.
At present there are approximately 25 research groups working on PEF applications for food
production. Though the technology has been explored almost 50 years ago, only a limited
amount of technical or industrial scale prototypes or commercial applications is available at
present. A transfer of successful results from laboratory to industrial scale showed to be a
difficult task.
This PEF system is part of a new food treatment system assembled by a DoD sponsored, University directed industry consortium. Diversified Technologies Inc., Bedford, MA, builds commercial PEF systems of processing volumes ranging from 500 to 2,000 liters per hour, with The Ohio State University supplying the PEF treatment chambers.
An industrial scale-up PEF pilot plant facility is available at The Ohio State University in the Department of Food Science and Technology. Food processors are invited to take advantage of the expertise of OSU faculty and staff, and facilities to conduct confidential product evaluations for food safety, quality, and shelf-life, and to obtain guidance on product development. A portable pilot scale PEF processing system is also available for customer-site evaluation. The resources at OSU can be accessed for a nominal fee.
Influence of the food matrix
The dielectric strength of the food matrix has a significant influence on the applicability of PEF, as dielectric breakdown has to be prevented. Air bubbles cannot withstand high electric field strengths. They may be present in sparkling products or be released due to temperature increase. In particular for microbial inactivation, where a higher electric field strength is required, air has to be removed from the product. Vacuum degassing or pressurizing the treatment media during PEF processing, using positive back pressure, can minimize the presence of air bubbles.
For treatment of solid foods, such as plant or animal material or fruit mashes, air encapsulations have to be removed to avoid electric discharges. Foam forming products might be unsuitable for PEF-treatment.