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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. Escherchia coli 0157:H7. Clostridium Botulin.
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Physics and Our Food Supply Kinetics of Microbial Inactivation for Alternative Food Processing Technologies Bruce Boehne - 2007
Typical Foodborne Pathogens Escherchia coli 0157:H7 Clostridium Botulin Salmonella Enteritidus
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 Technologiesthat Involve Physical PrincipalsTaught in Our Classes
High Pressure Processing • 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 • 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
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.
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.
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.
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.
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.
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.
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
Ohmic and Inductive Heating • The use of electrical resistance to heat food internally. • Advantages include rapid and uniform heating. • Food is literally “plugged in”
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.
Making the Connection • Bioterrorism • Frankenfood • Food Handling and Consumption • Building an awareness of our food supply • How are we going to use this stuff?
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: bruceboehne@netscape.net
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/May01/051601/her0001.pdf • http://vm.cfsan.fda.gov/~comm/ift-toc.html