1 Pulsed Electric Field
-
Upload
enrique-guzman -
Category
Documents
-
view
231 -
download
2
Transcript of 1 Pulsed Electric Field
-
8/14/2019 1 Pulsed Electric Field
1/11
V.B. Alvarez/PEF/10-2007
PULSED ELECTRICPULSED ELECTRICPULSED ELECTRICPULSED ELECTRICPULSED ELECTRICPULSED ELECTRICPULSED ELECTRICPULSED ELECTRICFIELD PROCESSINGFIELD PROCESSINGFIELD PROCESSINGFIELD PROCESSINGFIELD PROCESSINGFIELD PROCESSINGFIELD PROCESSINGFIELD PROCESSING
Valente B. AlvarezFood industries Center
Department of food Science andTechnology
PULSED ELECTRIC FIELDPULSED ELECTRIC FIELDPULSED ELECTRIC FIELDPULSED ELECTRIC FIELDPULSED ELECTRIC FIELDPULSED ELECTRIC FIELDPULSED ELECTRIC FIELDPULSED ELECTRIC FIELDPROCESSINGPROCESSINGPROCESSINGPROCESSINGPROCESSINGPROCESSINGPROCESSINGPROCESSING
Contents Principle Processing
parameters Applications and
effects
-
8/14/2019 1 Pulsed Electric Field
2/11
Application of short burst of high voltage(approx. 20-80 kV/cm) to foods placedbetween two electrodes pulses applied at ambient or refrigerated
temperatures for short treatment time ofseconds or less
Square wave, bipolar, oscillatory pulses orof exponentially decaying waves
Aseptic packaging and refrigerated storageafter treatment
Nonthermal method of food preservation
Pulse electric field (PEF)Pulse electric field (PEF)Pulse electric field (PEF)Pulse electric field (PEF)Pulse electric field (PEF)Pulse electric field (PEF)Pulse electric field (PEF)Pulse electric field (PEF)basic principlebasic principlebasic principlebasic principlebasic principlebasic principlebasic principlebasic principle
PEF PrinciplePEF Principle
Non-thermal inactivationof microorganisms thatresults from thepermeabilization orelectroporation of the cellmembrane
Depends on electric fieldintensity, pulse duration,and number of pulses.
DesbalanceOsmotico
Hinchamiento
Celula
Ruptura de laMembrana
Mechanism of inactivation
-
8/14/2019 1 Pulsed Electric Field
3/11
Critical process parametersCritical process parameters
PROCESS RELATED Electric field strength Total treatment time Pulse width Pulse polarity Treatment temperature Pulsed shape (Square
wave, exponentialdecay, oscillatorypulses)
Flow rate
PRODUCT RELATED Electrical conductivity pH Water activity (a w)
Bacteria > Yeasts Gram (+) > Gram (-) Bacterial spores & Mold ascospores > Vegetative
cells
Stationary or Lag growth phase > Logarithmicphase
Microbiological resistanceMicrobiological resistance
-
8/14/2019 1 Pulsed Electric Field
4/11
Log phase cells are more sensitivethan stationary phase cells
Spores are not inactivated(Mertens & Knorr, 1992; Gould, 2001)
Pulse electric field (PEF)Microbiology
Intrinsic and extrinsic factorsinfluencing effectiveness:
More inactivation with risingtemperatures
Low ionic strength favors inactivation Reduction in pH increase
inactivation(Qin et al., 1994; Jayaram et al., 1992)
Pulse Electric Field (PEF)Pulse Electric Field (PEF)Process ConditionsProcess Conditions
-
8/14/2019 1 Pulsed Electric Field
5/11
Resistivity in general decreases astemperature increases
Resistivity decreases as ionic strengthincreases Hulsheger and Niemann (1980) found the same level of E.
coli inactivation in buffers of NaCl, Na 2S 2O3, NaH 2PO 4,
The bactericidal effect of PEF is generallyinversely proportional to the ionicstrength of the material treated Wouters and Smelt, 1997
PEF process conditionsPEF process conditions
PEF: less thermal damage toPEF: less thermal damage tofoodsfoods
FLAVOR Cranberry juice treated with PEF was not
distinguishable from raw juice, although heattreated juice was.
Apple cider treated with PEF had nodetectable flavor differences from untreatedproduct when fresh
Orange juice PEF treated at 65 oC was preferredover heat pasteurized product, but not overuntreated product
-
8/14/2019 1 Pulsed Electric Field
6/11
PEF: less thermal damage toPEF: less thermal damage tofoodsfoods
COLOR Cranberry juice retained more
anthocyanin pigments after PEFprocessing than after heat treatment
Tomato salsa processed with PEFretained a brighter red color than heatprocessed product
No significant color differences were
seen in orange juice or in apple cider
PEF: less thermal damage toPEF: less thermal damage tofoodsfoods
NUTRITIONAL COMPONENTS Vitamin C loss was more significant in heat
treated orange juice than in PEF treated juice
PROTEIN COAGULATION
Coagulation in the treatment chamber leads toreduced flow, non-uniform or over- treatmentand eventually plugging of the chamber.
-
8/14/2019 1 Pulsed Electric Field
7/11
ISSUEISSUE THERMALTHERMAL PEFPEF
Mode of operation Batch/continuous Primarily continuous
Process in Package Yes No
Chemical changes Many Limited
Physical changes Many None
Enzyme Inactivation Yes Limited
Comparison between thermalComparison between thermalComparison between thermalComparison between thermalComparison between thermalComparison between thermalComparison between thermalComparison between thermalprocessing and PEFprocessing and PEFprocessing and PEFprocessing and PEFprocessing and PEFprocessing and PEFprocessing and PEFprocessing and PEF
Potential Food ApplicationsPotential Food ApplicationsPotential Food ApplicationsPotential Food Applications
Juice Milk Liquid eggs Soups
Syrups, sauces Emulsion Flavor ingredients
-
8/14/2019 1 Pulsed Electric Field
8/11
Electric resistivity of variousElectric resistivity of variousfood materialsfood materials
Zhang, et al., 1994
FoodsElectric
resistivity( -cm)
Conductivity
(mS/cm)
Testtemperature
(oC)
Apple juice 570 1.8 15Orange juice 234 4.3 42Orange juice conc. 300 3.3 15
Tomato ketchup 42 23.8 15Crushed tomatoes 125 8.0 50
Milk, skim 310 3.23 15Milk, raw 230 4.4 20
Yogurt 169 5.9 23Egg whites 155 6.5 15Liquid whole egg 170 5.9 21
The importance of pH in PEFThe importance of pH in PEFformulationsformulations
High acid foods are moresuccessfully treated with PEF Vegetative organisms are more effectively
treated at lower pH
product is a high acid or acidified food (pH
-
8/14/2019 1 Pulsed Electric Field
9/11
PEF Advantages & disadvantagesPEF Advantages & disadvantages
Limitations due to thedifficulty of inactivatingendospores and lowconductivity caused bysolids in foods.
Regulatory requirementsdeveloping
Difficult to incorporatenecessary equipment intomost production areas
High quality fresh-likeliquid foods
Improve flavor, nutritionalvalue, and Shelf life
Foods retain their fresharoma, taste, andappearance
Energy efficient processcompare to thermal
processing(Ramaswamy, 2003)
Combination processesCombination processes
PEF may offer synergistic effect with Ultrasound Temperature Chemical & additives
e.g. Bacteriocin
High pressure Sequential or simultaneous
-
8/14/2019 1 Pulsed Electric Field
10/11
PEF Work at OSU
Raw & UHT skim milk were PEFprocessed 0.3 to 3.0 log reduction of P.
fluorescens , L. lactis and B. cereus and of total m.o.s in raw skim milk
No changes in protein, total solids,color, pH, particle size, and densitydue to PEF effects
Overall effectiveness of PEF vs.
Pasteurization (73oC for 30s)(Alvarez et al., 2003)
Microbial Inactivation of Microbial Inactivation of Microbial Inactivation of Microbial Inactivation of Microbial Inactivation of Microbial Inactivation of Microbial Inactivation of Microbial Inactivation of Pulsed Electric Field Treated MilkPulsed Electric Field Treated MilkPulsed Electric Field Treated MilkPulsed Electric Field Treated MilkPulsed Electric Field Treated MilkPulsed Electric Field Treated MilkPulsed Electric Field Treated MilkPulsed Electric Field Treated Milk
-3.5
-3
-2.5
-2
-1.5
-1
-0.5
047 94 141 188
Treatment Time ( s)
L o g r e
d u c
t i o n s ,
N / N o
( c f u m
L - 1
)
P.fluorescens L. lactis B. cereus Microorganisms in Raw Skim Milk
-6
-5
-4
-3
-2
-1
0P. fluorescens L. lactis B.cereus
Microorganisms inRaw Skim Milk
L o g r e
d u c
t i o n ,
N / N o ( c
f u m
L - 1
)
Pasteurization PEF
Source: Michalac, Alvarez..., 2003
-
8/14/2019 1 Pulsed Electric Field
11/11
PULSED ELECTRIC FIELDPULSED ELECTRIC FIELDPULSED ELECTRIC FIELDPULSED ELECTRIC FIELDPULSED ELECTRIC FIELDPULSED ELECTRIC FIELDPULSED ELECTRIC FIELDPULSED ELECTRIC FIELDPROCESSINGPROCESSINGPROCESSINGPROCESSINGPROCESSINGPROCESSINGPROCESSINGPROCESSING
Summary Principle Processing
parameters Applications and
effects
References (PEF)References (PEF) Bendicho, S., Barbosa-canovas, G.V., and Martin, O.
2002. Milk processing by high intensity pulsedelectric fields. Trends in Food Science & Technology,13, 195-204.
Michalac, S., Alvarez, V. B., Ji, T., and Zhang, Q.2003. Inactivation of Selected Microorganisms andProperties of Pulsed Electric Field Processed Milk. J.Food Proc. and Preservation . 27 (2). 137-151.
Ramaswamy, R., Jin, T., Balasubramaniam, V.M.,and Zhang, H. 2005. Pulsed electric field processing.Factsheet for food processors (FSE 2-05), The OhioState University, Columbus, OH, U.S.A.(http://ohioline.osu.edu/fse-fact/0002.html)
Wouters, P.C., Alvarez, I., and Raso, J. 2001.Critical factors determining inactivation kinetics bypulsed electric field food processing. Trends in FoodScience & Technology, 12, 112-121.