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Howard Zhang and chemical engineer David Geveke operate lab equipment used for testing pulsed electric field and radio-frequency electric field treatments. Link to photo information
In studies of methods to pasteurize liquid foods such as apple cider without using heat, research leader Howard Zhang (left) and chemical engineer David Geveke develop and evaluate pulsed electric field and radio-frequency electric field treatments. Click the image for more information about it.

Nonthermal Food Processing Heats Up

By Laura McGinnis
October 18, 2006

Technologies such as high-pressure processing, ultraviolet light and irradiation can be faster, cheaper and less disruptive to food quality than traditional thermal processing for killing microbes that can contaminate food products, according to scientists with the Agricultural Research Service (ARS).

Under the guidance of research leader Howard Zhang, scientists at ARS' Eastern Regional Research Center (ERRC) in Wyndmoor, Pa., have investigated the effectiveness of these and other antimicrobial methods.

High-pressure processing (HPP) treatment involves applying 80,000 to 130,000 pounds per square inch of pressure to a sample. The researchers found that applying that extreme pressure for two to five minutes will inactivate the majority of microorganisms on or in a food source.

While HPP can eliminate close to 100 percent of vegetative microorganisms, it is not effective at removing microbial spores. In addition, at a cost of 5 to 10 cents per pound, it's too pricey to be practical. Zhang hopes that future research will change that.

The scientists have also investigated ultraviolet (UV) light and irradiation to protect food. They used UV processing on an apple cider sample that had been inoculated with bacteria. The UV treatment compared favorably to heat pasteurization, reducing the pathogen populations by more than 99 percent without changing the cider's flavor.

Irradiation exposes food to a low level of ionizing radiation to inactivate molds, yeasts, parasites, bacteria and other microorganisms that can lead to food spoilage and illness. Studies show that eating irradiated foods poses no increased health risk for consumers.

ERRC research findings have enabled federal regulatory agencies to establish standards to ensure the safety and quality of irradiated products like fruit, vegetables, juice, meat and meat substitutes.

Read more about this and other food safety research in the October 2006 issue of Agricultural Research magazine.

ARS is the U.S. Department of Agriculture's chief scientific research agency.