Transcript Physics and Our Food Supply - Southern Methodist University

Physics and Our Food
Supply
Kinetics of Microbial Inactivation
for Alternative Food Processing
Technologies
Bruce Boehne - 2007
Applications of Physics to Our Food
Supply
Physics Applied to Our Food
Overview
Typical Foodborne Pathogens
Clostridium
Botulin
Escherchia
coli 0157:H7
Salmonella
Enteritidus
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How do you kill off the bad stuff without
ruining the food?
What applications of physics are useful to food
safety?
How can we use food to connect the principals
taught in our classes to the real world?
Food Processing
Technologies
that Involve Physical
Principals
Taught in Our Classes
High Pressure Processing
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Exposing food to 50,000 to 100,000 psi from 30
seconds to one minute.
High pressure interferes with a pathogen’s life
processes.
Food is mostly water so high pressure does not
crush it and does not affect taste or nutritional
value.
Soups, jams, guacamole, dressings, salsa.
Pulsed Electric Field
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Place food between two electrodes and pulse 2080 kV/cm for less than one second
Used mainly to enhance food quality
Restricted to food products that have low
conductivity and do not contain or form
bubbles.
Needs further study
High Voltage Arc Discharge
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Done by applying rapid discharge voltages
through electrodes in a solution.
Creates an intense pressure wave and produces
new chemical compounds through electrolysis.
Shows promise but still under study.
Pulsed Light
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Involves the use of intense short duration pulses
of broad spectrum white light.
Used mainly to reduce microbial populations on
packaging or food surfaces.
More research needed on the exact mechanisms
involved in inactivation of pathogens.
Oscillating Magnetic Fields
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Have been explored but the effects are
controversial.
Food is placed in a plastic bag and subjected to 1
to 100 pulses with a frequency of 5 to 500 kHz
for a total exposure time of 25 to 100 ms.
Results have been inconsistant.
Ultraviolet Light
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UVC (200-280 nm wavelength) has germicidal
properties due to DNA mutation effects.
UV exposure must be at least 400 J/sq m in all
parts of the product to be effective.
Used mainly to treat juices, water supplies, and
food contact surfaces.
Ultrasound
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In the range of 20,000 Hz +
Causes intracellular cavitation (micro-mechanical
shocks) that distrupt cell structures up to the
point of cell membrane disruption.
Very tricky to get all the variables just right.
Pulsed X-Rays
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Has the advantage of being very precise, having
high depth of penetration, and by pulsing the
negative effects of irradiation can be somewhat
mitigated.
Pulses can last from 1-30 ns up to 1000 pulses
per second.
Irradiation
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Food passes quickly through a radiation field-typically gamma rays produced from radioactive
cobalt-60.
Irradiation interferes with bacterial genetics, so
the contaminating organism can no longer
survive or multiply.
Dosages in kiloGrays (1 kGy – death to insects)
Mostly used today for dried spices
Ohmic and Inductive Heating
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The use of electrical resistance to heat food
internally.
Advantages include rapid and uniform heating.
Food is literally “plugged in”
Microwave and Radio Frequency
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Found to be unreliable to non-uniform heating
– cold spots.
As food heats microwave absorption properties
change and location of the cold spot shifts.
The coldest location determines the level of
safety.
Making the Connection
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Bioterrorism
Frankenfood
Food Handling and Consumption
Building an awareness of our food supply
How are we going to use this stuff ?
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Science and Our Food Supply –
Investigating Food Safety from Farm to Table
A Teacher’s Resource Kit for both Middle and
High School Science teachers.
Feel free to contact me for assistance in using this
in your classroom: [email protected]
References
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http://www.cfsan.fda.gov/~comm/ift-xray.html
http://www.cfsan.fda.gov/~dms/opafdir.html
http://www.cfsan.fda.gov/~comm/ift4-5.html
http://www.cfsan.fda.gov/~dms/3fs3re09.html
http://www.fda.gov/ohrms/dockets/dailys/01/
May01/051601/her0001.pdf
http://vm.cfsan.fda.gov/~comm/ift-toc.html