Physics and Our Food Supply

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Physics and Our Food Supply

• Kinetics of Microbial Inactivation for
  Alternative Food Processing Technologies

Bruce Boehne - 2007
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Applications of Physics to Our Food Supply
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Physics Applied to Our Food
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Overview
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Typical Foodborne Pathogens
Escherchia coli 0157H7
Clostridium Botulin
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?

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Food Processing Technologiesthat Involve
Physical PrincipalsTaught in Our Classes
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High Pressure Processing

• Exposing food to 50,000 to 100,000 psi from 30
  seconds to one minute.
• High pressure interferes with a pathogens 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.

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Pulsed Electric Field

• Place food between two electrodes and pulse 20-80
  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

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High Voltage Arc Discharge

• 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.

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Pulsed Light

• 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.

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Oscillating Magnetic Fields

• 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.

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Ultraviolet Light

• 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.

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Ultrasound

• 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.

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Pulsed X-Rays

• 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.

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Irradiation

• 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

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Ohmic and Inductive Heating

• The use of electrical resistance to heat food
  internally.
• Advantages include rapid and uniform heating.
• Food is literally plugged in

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Microwave and Radio Frequency

• 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.

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Making the Connection

• 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 Teachers Resource Kit for both Middle and High
  School Science teachers.
• Feel free to contact me for assistance in using
  this in your classroom bruceboehne_at_netscape.net

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References

• http//www.cfsan.fda.gov/comm/ift-xray.html
• http//www.cfsan.fda.gov/dms/opa-fdir.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/May01/0
  51601/her0001.pdf
• http//vm.cfsan.fda.gov/comm/ift-toc.html