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June 2, 2006

Vermelding onderdeel organisatie

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Pulsed Elect r ic Fields (PEF)The alt ernative w ay for preservat ion ofliquid food product s

Waldur Symposium 2006 Pulsed Pow er Eindhoven

Treatment system for 500 L/h in our Laboratory

1860

2003Bart Roodenburg

Electrical Power Processing EPP


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Contents

Why food preservation PEF applications

EET-PEF project PEF inactivation principle Project objectives

Up scaling to industrial volumes

System design (pulse generator, chambers & hydraulicsystem) Experiments

Inactivation tests

Product tests

Metal release and electrode wear Future Conclusions


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Why food preservat ion

Prevent illness

#costs 1800 M/year (NL)

Prevent food spoilage Increase shelf life

Methods

Pasteurisation (Louis Pasteur, 1822-1895)

Temperature 70 - 80C

Sterilisation

Temperature 130 - 180C

PEF

Temperature 40 - 50CPEF (Temp & E-field)

pasteurization (Temp)

#35% (working population) of 2.2 million people for 3 days, 8h a 100


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PEFApplications: pasteurisation of liquids(juices, beer, sauces, soft drinks )

optimise drying processes Effect on: micro organisms

Limitations:

homogeneous liquids no spore inactivation

General: save energy #

higher nutritional value better colour and taste

# Saving in case of PEF: 4 kJ / kgK at (80-50) results in 120 kJ / kg productYear consumption of juices and soft drinks in NL 3109 Litre, which results in 360 TJ/yearor 100 GWh, 5 million / Year


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EET-PEF project

Subsidised project (Dutch government)

Partners Dutch PEF consortium

Stork food and Dairy (equipment) Unilever

Friesland foods

TNO

Universities (Wageningen & Delft)

Project aims

Further develop mild preservation

Up scaling

Save energy (pasteurisation)

Better products


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PEF inact ivat ion pr inciple

Electric field 2..4kV/mm, pulsed 1..10s

A: Voltage across membrane

B: Compression C: Pore formation

D: Irreversible pores

Cell death


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Project object ives

Up scaling

From lab scale [ml/min] to

Industrial plant scale [

#

5..10 m

3

/h] System design

(Pulsed) power electronics

Continuous flow treatment chamber

Hydraulic system

Sensorial tests

Determination of product changes

#16 h/day, 6 days/week, 50 weeks with 5,000 L/h = 24 million L/year


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Up scaling

Create a step in between

[ml/min] to [m3/h]; 15,000 times

System specification our Testplatform Product flow up to 500 L/h

Large system flexibility

Easy exchange of treatment chambers Output U/I: 080 kV / 01000 A

Repetition rate: 1500 Hz

Pulse duration: 14 s

Product conductivity range ~0.32.5 S/m (i.e. Beer, Fruitjuices, Milk, sauces )


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System design

Pulse generation via:

Charging lumped transmission line (i.e. PFN)

Voltage step up to 80 kV Stacked thyristors or thyratron switches

Continuous flow treatment system

charger

lumped

T-line withthyratron

pulse

transformer

treatment

chamber

pump

cooling

storage

tank

P

1 : 4

40 kV


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Pulse generat ion


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Chamber design (1)

Continuous flow

Easy and cheap to manufacture (SS electrodes, lifetime)

Investigated chamber types:

Co-field

Cross-field

Co-flow

Main differences

Flow & field direction

Electrode shape

Cooling

Hygienic design


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Chamber design (2)

Avoid partial discharges (pds), causedin vapour bubbles

Why?

Can lead to full break down

Affect product quality

How? Avoid too high local electric fields

Pressurize the system (bubble

shrinking)

Partial discharge


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Chamber design (3)

Relationship between applied voltage, pds,temperature rise and pressure


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Chamber design (4)

The maximum intensity of PEF treatment withoutpartial discharges depends strongly on chamber

geometry

Co-flow, 140 J/ml (less hygienic)

Co-field, 90 J/ml Cross-field, 45 J/ml

Co-field and Co-flow chamber has been used duringthe product- and inactivation tests


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Experiments

Inactivation tests

Buffer inoculated with bacteria or yeast e.g.

Candida magnolia Influence of electric parameters, E-field, pulse

duration

Product tests Orange juice (mostly spoiled by yeast)

Change sensorial quality (taste panel)

Product change due to electrode wear


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I nact ivat ion test s

Electrical influences

Applied Electric field

Pulse duration


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Product t est s

Orange juice

Keeping quality (THT)

Taste in relation to fresh squeezed

A: Fresh squeezed unprocessed spoiled after 7 days

B: PEF treated (50C), fresh like taste, THT 21 days

Advantages: better taste and shelf life extension

A B


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Met al release due t o w ear (1)

Electrodes Stainless steel, why?

commonly accepted in

food industry cheap & easy to shape

Reducing-oxidizingreactions at electrodes

Main species of SS canbe found in theproduct Iron, Nickel


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Met al release due t o w ear (2)

PEF treated Orange juice Additional Iron (Fe) 15 g/kg

Additional Nickel (Ni) 0.2 g/kg

Relationship with European legislation rules

Nothing mentioned in Dutch warenwet

LegislationFe

[g/kg]

Ni[g/kg]

European A.I.J.N. code (Fruit Juices) 5,000 -

Codex standard 45-1981 15,000 -

Drinking water directive 98/83/EG 200 50


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Product

flow

Future

Up scaling from 0.5m3

/h to 20m3

/h

General investment in Pulsed Power Energy saving due to PEF: 0.2 cent/L

Investment to use PEF: 0.8 cent/L

PEF in-pack (ongoing STW project)

Product is packed untreated Package has integrated electrodes No contamination afterwards

Integrated treatment systems Product is treated just before use Combat feeding U.S. army


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Conclusions Food preservation is from main importance

Considerations of health Economical point of view

PEF results in

Alternative for pasteurisation Fresh like taste (especially for fruit juices) Saves energy

EET-PEF project gives us more insight in Effect of electrical parameters on inactivation, wear, product quality Electrode wear in relation to legislation rules Up scaling matters (pilot-plant for 500 L/h)

Product tests on fresh squeezed Orange juice results in Shelf life increase from 7 to 21 days PEF treated juice tastes like fresh juice


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Thank you for your at t ent ion

[email protected]

http://ee.ewi.tudelft.nl/epp/

http://www.senternovem.nl/eet/

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