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SoldierTech: High-Pressure Processing Keeps Food Safe

KILLING PATHOGENS: High-Pressure Processing Keeps Food Safe

 

E. Coli, Salmonella and Listeria -- if consumed, these pathogens can make you as sick as a dog. Fortunately, high-pressure processing kills all of these and even sterilizes intravenous solutions and antigens for innoculation.

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Plastic tubes are used for pouch food while a metal tube is designed for foods in a can. Processing time is much faster using high pressure. (Courtesy Photo)

Pressed inside a vessel exerting 70,000 pounds per square inch or more, food can be processed so that it retains its fresh appearance, flavor, texture and nutrients while disabling harmful microorganisms and slowing spoilage.

High-pressure processing, an idea more than a century old, was resurrected in the past decade under the joint leadership of Patrick Dunne, a senior research chemist at the Department of Defense Combat Feeding Directorate at the U.S. Army Soldier Systems Center in Natick, Mass., and Edmund Ting of Avure Technologies Inc., in Kent, Wash.

Its potential is now being realized in the commercial market and in the future may lead to a wide array of appealing shelf-stable combat rations for warfighters.

“(High-pressure processing) has been quoted as being the best innovation in food processing in 50 years,” Dunne said, who's also the senior adviser for advanced processing and nutritional biochemistry at Combat Feeding. “It's another dimension of food processing that gives a cleaner (ingredient) label with fewer additives and in some cases improves texture.”

Although first discovered in the 1890s, high-pressure processing was dormant technology until the late 1980s, according to Dunne. His expertise in understanding microbial inactivation by high pressure and benefits of minimizing chemical changes in foods during and after processing was teamed with Ting and engineers from Avure, who developed the equipment to produce high-pressure processed foods.



Whole meats are preserved in a similar fashion. (Courtesy Photo)

Using hydrostatic pressure, water is pumped into a sturdy closeable steel vessel. Foods of any shape or size are equally squeezed around its surface area without crushing the food particles. It's effective on most moist foods, such as fruits, vegetables, sauces and ready-to-eat meats. It can even shell whole uncooked lobster.

“It rapidly and uniformly inactivates bacteria by injuring the protein and other key cellular structures that would be necessary for growth and function of bacteria. It also inactivates viruses,” Dunne said.

The high pressure cycle takes no longer than six minutes, compared to traditional high-temperature processing that takes an hour or longer, without causing chemical changes that degrade food quality.

The process is the only Food and Drug Administration and U.S. Department of Agriculture-approved technology that can kill E. coli, Salmonella and Listeria pathogens inside packaged food products without additives or additional heat processing, according to Dunne, but there's one pathogen still to overcome.

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“Clostridium botulinum has been a stumbling block to commercialization of low-acid, shelf-stable foods,” Dunne said. “It still has to be demonstrated on a prototype unit before the next step of full-scale research for a bigger production rate.”

A family of acidified shelf-stable items -- including seafood jambalaya, oriental chicken and Southwestern pasta -- was initially demonstrated at Natick under a contract to Oregon State University led by Professor Daniel Farkas in the 1990s with a longer than two-year shelf-life, he said, but processing equipment was too expensive for commercial application.

By 2001, Avure developed highly-reliable equipment to meet demand for a variety of extended shelf-life refrigerated products. Food companies are using the process for products ranging from orange juice to guacamole to deli meats, which are sold at major stores across the country.

Dunne said the next step for the Army is to develop a high-pressure-assisted thermal sterilization process in low-acid foods, which is expected to be approved by regulatory agencies this year.

Working with industry and academia, Combat Feeding food technologists want to investigate making shelf-stable acidified and low-acid foods, such as potatoes, pasta, rice, whole-muscle meats, seafood and eggs, Dunne said.



Food companies are using high pressure processing for products such as guacamole (above), which is sold at major stores across the country. (Courtesy Photo)

Mashed potatoes processed with a new high-pressure sterilization unit might be ready for field testing by the end of the year, he said. Egg products are a longer-term goal. Both degrade in quality during traditional processing.

“It's a new era where industry is collaborating in funding equipment and research on the inactivation of pathogens,” Dunne said. “Maybe in another three years, there will be a large enough commercial base to produce pressure-sterilized shelf-stable foods, and we hope beginning with the military.”

Beyond the food industry, high-pressure technology could lead to the processing of biological pharmaceutical products and specialized intravenous solutions, or lead to development of a human vaccine from pressure-inactivated viruses serving as antigens for inoculation.

High-pressure processing won a 2005 Federal Laboratory Consortium Award for Excellence in Technology Transfer, which will be presented to Dunne and Ting in May.

The award recognizes laboratory employees who have accomplished outstanding work in the process of transferring federally-developed technology to the marketplace. A panel of experts from industry, state and local government, academia and federal laboratory system judge nominations.

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Copyright © 2005 Military.com.

 
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