Physics and Our Physics and Our Food SupplyFood SupplyKinetics of Microbial Kinetics of Microbial

Inactivation for Alternative Inactivation for Alternative Food Processing Food Processing

TechnologiesTechnologies

Bruce Boehne - 2007

Applications of Physics to Applications of Physics to Our Food SupplyOur Food Supply

Physics Applied to Our Physics Applied to Our FoodFood

OverviewOverview

Typical Foodborne Typical Foodborne PathogensPathogens

Clostridium

Botulin

Escherchia coli 0157:H7

Salmonella

Enteritidus

How do you kill off the bad stuff How do you kill off the bad stuff without ruining the food?without ruining the food?

What applications of physics are What applications of physics are useful to food safety?useful to food safety?

How can we use food to connect the How can we use food to connect the principals taught in our classes to principals taught in our classes to the real world?the real world?

Food Processing Food Processing TechnologiesTechnologiesthat Involve that Involve

Physical PrincipalsPhysical PrincipalsTaught in Our Taught in Our

Classes Classes

High Pressure High Pressure ProcessingProcessing

Exposing food to 50,000 to 100,000 Exposing food to 50,000 to 100,000 psi from 30 seconds to one minute.psi from 30 seconds to one minute.

High pressure interferes with a High pressure interferes with a pathogen’s life processes.pathogen’s life processes.

Food is mostly water so high pressure Food is mostly water so high pressure does not crush it and does not affect does not crush it and does not affect taste or nutritional value.taste or nutritional value.

Soups, jams, guacamole, dressings, Soups, jams, guacamole, dressings, salsa. salsa.

Pulsed Electric FieldPulsed Electric Field

Place food between two electrodes Place food between two electrodes and pulse 20-80 kV/cm for less than and pulse 20-80 kV/cm for less than one secondone second

Used mainly to enhance food qualityUsed mainly to enhance food quality Restricted to food products that Restricted to food products that

have low conductivity and do not have low conductivity and do not contain or form bubbles.contain or form bubbles.

Needs further studyNeeds further study

High Voltage Arc High Voltage Arc DischargeDischarge

Done by applying rapid discharge Done by applying rapid discharge voltages through electrodes in a voltages through electrodes in a solution.solution.

Creates an intense pressure wave Creates an intense pressure wave and produces new chemical and produces new chemical compounds through electrolysis.compounds through electrolysis.

Shows promise but still under study.Shows promise but still under study.

Pulsed LightPulsed Light

Involves the use of intense short Involves the use of intense short duration pulses of broad spectrum duration pulses of broad spectrum white light.white light.

Used mainly to reduce microbial Used mainly to reduce microbial populations on packaging or food populations on packaging or food surfaces.surfaces.

More research needed on the exact More research needed on the exact mechanisms involved in inactivation mechanisms involved in inactivation of pathogens.of pathogens.

Oscillating Magnetic Oscillating Magnetic FieldsFields

Have been explored but the effects Have been explored but the effects are controversial.are controversial.

Food is placed in a plastic bag and Food is placed in a plastic bag and subjected to 1 to 100 pulses with a subjected to 1 to 100 pulses with a frequency of 5 to 500 kHz for a total frequency of 5 to 500 kHz for a total exposure time of 25 to 100 ms.exposure time of 25 to 100 ms.

Results have been inconsistant.Results have been inconsistant.

Ultraviolet LightUltraviolet Light

UVC (200-280 nm wavelength) has UVC (200-280 nm wavelength) has germicidal properties due to DNA germicidal properties due to DNA mutation effects.mutation effects.

UV exposure must be at least 400 UV exposure must be at least 400 J/sq m in all parts of the product to J/sq m in all parts of the product to be effective.be effective.

Used mainly to treat juices, water Used mainly to treat juices, water supplies, and food contact surfaces.supplies, and food contact surfaces.

UltrasoundUltrasound

In the range of 20,000 Hz +In the range of 20,000 Hz + Causes intracellular cavitation Causes intracellular cavitation

(micro-mechanical shocks) that (micro-mechanical shocks) that distrupt cell structures up to the distrupt cell structures up to the point of cell membrane disruption.point of cell membrane disruption.

Very tricky to get all the variables Very tricky to get all the variables just right.just right.

Pulsed X-RaysPulsed X-Rays

Has the advantage of being very Has the advantage of being very precise, having high depth of precise, having high depth of penetration, and by pulsing the penetration, and by pulsing the negative effects of irradiation can be negative effects of irradiation can be somewhat mitigated.somewhat mitigated.

Pulses can last from 1-30 ns up to Pulses can last from 1-30 ns up to 1000 pulses per second.1000 pulses per second.

IrradiationIrradiation

Food passes quickly through a radiation Food passes quickly through a radiation field--typically gamma rays produced field--typically gamma rays produced from radioactive cobalt-60. from radioactive cobalt-60.

Irradiation interferes with bacterial Irradiation interferes with bacterial genetics, so the contaminating organism genetics, so the contaminating organism can no longer survive or multiply. can no longer survive or multiply.

Dosages in kiloGrays (1 kGy – death to Dosages in kiloGrays (1 kGy – death to insects)insects)

Mostly used today for dried spicesMostly used today for dried spices

Ohmic and Inductive Ohmic and Inductive HeatingHeating

The use of electrical resistance to The use of electrical resistance to heat food internally.heat food internally.

Advantages include rapid and Advantages include rapid and uniform heating.uniform heating.

Food is literally “plugged in”Food is literally “plugged in”

Microwave and Radio Microwave and Radio FrequencyFrequency

Found to be unreliable to non-Found to be unreliable to non-uniform heating – cold spots.uniform heating – cold spots.

As food heats microwave absorption As food heats microwave absorption properties change and location of properties change and location of the cold spot shifts.the cold spot shifts.

The coldest location determines the The coldest location determines the level of safety.level of safety.

Making the ConnectionMaking the Connection

BioterrorismBioterrorism FrankenfoodFrankenfood Food Handling and ConsumptionFood Handling and Consumption Building an awareness of our food Building an awareness of our food

supplysupply How are we going to use this stuff?How are we going to use this stuff?

Science and Our Food Supply – Science and Our Food Supply –

Investigating Food Safety from Farm to Investigating Food Safety from Farm to TableTable

A Teacher’s Resource Kit for both Middle and A Teacher’s Resource Kit for both Middle and High School Science teachers.High School Science teachers.

Feel free to contact me for assistance in Feel free to contact me for assistance in using this in your classroom: using this in your classroom: bruceboehne@netscape.netbruceboehne@netscape.net

ReferencesReferences http://www.cfsan.fda.gov/~comm/ift-xray.hthttp://www.cfsan.fda.gov/~comm/ift-xray.ht

mlml http://www.cfsan.fda.gov/~dms/opa-http://www.cfsan.fda.gov/~dms/opa-

fdir.htmlfdir.html http://www.cfsan.fda.gov/~comm/ift4-http://www.cfsan.fda.gov/~comm/ift4-

5.html5.html http://www.cfsan.fda.gov/~dms/http://www.cfsan.fda.gov/~dms/

3fs3re09.html3fs3re09.html http://www.fda.gov/ohrms/dockets/dailys/http://www.fda.gov/ohrms/dockets/dailys/

01/May01/051601/her0001.pdf01/May01/051601/her0001.pdf http://vm.cfsan.fda.gov/~comm/ift-toc.htmlhttp://vm.cfsan.fda.gov/~comm/ift-toc.html