Download - 2 Ohmic Processing
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8/22/2019 2 Ohmic Processing
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OhmicOhmic HeatingHeating(Electrical Resistance Heating(Electrical Resistance Heating(Electrical Resistance Heating(Electrical Resistance Heating(Electrical Resistance Heating(Electrical Resistance Heating(Electrical Resistance Heating(Electrical Resistance Heating
or Electro heating)or Electro heating)or Electro heating)or Electro heating)or Electro heating)or Electro heating)or Electro heating)or Electro heating)
Valente B. AlvarezFood industries Center
Department of food Science and
Technology
OhmicOhmic HeatingHeating
Contents
Ohmic principle
Processparameters
Microbial
inactivation
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Basic principleBasic principle
Dissipation of electrical energyinto heat
Results in internal energygeneration
- proportional to the square ofelectric field strength and theelectrical conductivity
Electrical conductivity functionof temperature, material, and
method of heating
Food is made as apart of electricalcircuit
Alternating electriccurrent is passedthrough the food
Food act as a resistorto passage ofelectrical current
This causes heatgenerationP = I2 R
(P power, I current,R resistance)
R
L
V
))(1(A
LR
=
R Product resistance (ohms)L - Length (m)
A - Area
- electrical conductivity
(S/m)
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Ohmic heating and
microbial inactivation Main mechanism
like thermal process, inactivation by heat
Additional non-thermal electroporation at50-60 Hz
Electrical charges build up and formpores across microbial cells
(Wang, W.C., 1995)
AdvantagesAdvantages
Rapid heating
Reduce the total thermal abuse
Benefit heat sensitive foods (able to heatproteinaceous materials)
Suitable for continuous processing
lower capital cost than microwave Environmentally friendly
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Potential commercialPotential commercialapplications:applications: Aseptic processing of high
value added foods
pre-heating productsbefore canning
blanching, evaporation,dehydration, fermentation,and extraction
Critical process parametersCritical process parameters
Temperature and time are the principalcritical process factors
Other factors of interest include electrical conductivity(ies) of the respective
phases of the food,
temperature dependence of electricalconductivity,
design of the heating device,
extent of interstitial fluid motion,
residence time distribution (if any),
thermo physical properties of the food, and
electric field strength.
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Electrical conductivity of foodsElectrical conductivity of foods
0.34
4.3
Starch
with 0.2% salt
with 2% salt
0.42Beef
0.17Pea
0.041Carrot
0.037Potato
Electrical conductivity (S/m)Food
Electrical conductivity of foods is a function of temperature
Ohmic heating andmicrobial inactivation
Limitations & On-going research
Coupling between temperature,electrical and flow field
Shape and orientation issues
Economically viable for premiumquality foods
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Ohmically processed
commercial products
In the U.S. Canned low-acid particulate product
Pasteurized liquid egg
Italy, Greece, France, Mexico, andJapan Sliced, diced, and whole fruit within
sauces
Regulations
For in-container process
Similar to that of traditional thermalprocessing
Continuous flow processing andaseptic packaging
Under development by FDA and USDA
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OhmicOhmic HeatingHeating
Summary Ohmic principle
Processparameters
Applications andmicrobialinactivation
References (References (OhmicOhmic heating)heating) Sastry, S.K. 2003. Ohmic heating. Encyclopedia of
Agricultural, Food and Biological Engineering, MarcelDekker, Inc. 707-711.
Ramaswamy, R., Balasubramaniam, V.M., andSastry, S.K. 2005. Ohmic heating Fact sheet forfood processors (FSE 4-05). The Ohio StateUniversity, Columbus, OH, U.S.A.(http://fst.osu.edu/Ohmicfactsheet.pdf)
Wang, D.C. 1995. Ohmic heating of foods: Physical
properties and applications. Ph.D. Dissertation. TheOhio State University, Columbus, OH.
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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.
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.