Physics and Our Food Supply Kinetics of Microbial Inactivation for Alternative Food Processing Technologies Bruce Boehne

Applications of Physics to Our Food Supply

Physics Applied to Our Food

Overview

Typical Foodborne Pathogens Clostridium Botulin Escherchia coli 0157:H7 Salmonella Enteritidus

How do you kill off the bad stuff without ruining the food? How do you kill off the bad stuff without ruining the food? What applications of physics are useful to food safety? 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? 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 Exposing food to 50,000 to 100,000 psi from 30 seconds to one minute. Exposing food to 50,000 to 100,000 psi from 30 seconds to one minute. High pressure interferes with a pathogen’s life processes. 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. Food is mostly water so high pressure does not crush it and does not affect taste or nutritional value. Soups, jams, guacamole, dressings, salsa. Soups, jams, guacamole, dressings, salsa.

Pulsed Electric Field Place food between two electrodes and pulse kV/cm for less than one second Place food between two electrodes and pulse kV/cm for less than one second Used mainly to enhance food quality Used mainly to enhance food quality Restricted to food products that have low conductivity and do not contain or form bubbles. Restricted to food products that have low conductivity and do not contain or form bubbles. Needs further study Needs further study

High Voltage Arc Discharge Done by applying rapid discharge voltages through electrodes in a solution. Done by applying rapid discharge voltages through electrodes in a solution. Creates an intense pressure wave and produces new chemical compounds through electrolysis. Creates an intense pressure wave and produces new chemical compounds through electrolysis. Shows promise but still under study. Shows promise but still under study.

Pulsed Light Involves the use of intense short duration pulses of broad spectrum white 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. Used mainly to reduce microbial populations on packaging or food surfaces. More research needed on the exact mechanisms involved in inactivation of pathogens. More research needed on the exact mechanisms involved in inactivation of pathogens.

Oscillating Magnetic Fields Have been explored but the effects are controversial. 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. 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. Results have been inconsistant.

Ultraviolet Light UVC ( nm wavelength) has germicidal properties due to DNA mutation effects. UVC ( 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. 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. Used mainly to treat juices, water supplies, and food contact surfaces.

Ultrasound In the range of 20,000 Hz + 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. 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. 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. 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. 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. 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. Irradiation interferes with bacterial genetics, so the contaminating organism can no longer survive or multiply. Dosages in kiloGrays (1 kGy – death to insects) Dosages in kiloGrays (1 kGy – death to insects) Mostly used today for dried spices Mostly used today for dried spices

Ohmic and Inductive Heating The use of electrical resistance to heat food internally. The use of electrical resistance to heat food internally. Advantages include rapid and uniform heating. Advantages include rapid and uniform heating. Food is literally “plugged in” Food is literally “plugged in”

Microwave and Radio Frequency Found to be unreliable to non-uniform heating – cold spots. Found to be unreliable to non-uniform heating – cold spots. As food heats microwave absorption properties change and location of the cold spot shifts. As food heats microwave absorption properties change and location of the cold spot shifts. The coldest location determines the level of safety. 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 – Science and Our Food Supply – Investigating Food Safety from Farm to Table 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:

References xray.html xray.html xray.html xray.html fdir.html fdir.html fdir.html fdir.html /May01/051601/her0001.pdf /May01/051601/her0001.pdf /May01/051601/her0001.pdf /May01/051601/her0001.pdf