Engineering R&D: Move over, retort

February 1, 2010
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The math of commercial cost and consumer willingness to pay remains to be calculated, but in-container sterilization with microwaves already has achieved several milestones.

Researchers at Washington State University used a 40 KW pilot-scale microwave system to produce sterile, low-acid foods. Source: Washington State University.

Juming Tang, professor of food engineering, Washington State University, Pullman, WA. Source: Washington State University

Scientific proof of the consistency and reliability of new processing technologies has stopped cold more than one novel process with the potential to improve the taste and nutritional quality of food. When the FDA recently approved a microwave sterilization process for prepackaged mashed potatoes that will remain safe at ambient temperatures, researchers at Washington State University (WSU) achieved what several novel processes had failed to do: they validated to regulators that they could deliver a safe product with an unconventional process.

The WSU system was patented in 2006, and a 76-by-12 ft. pilot unit went into service soon after in the pilot plant at WSU’s Pullman, WA campus, processing salmon fillets and other low-acid foods. But developing a computer-vision method based on chemical-marker formation to determine the cold spot in trays being conveyed through the system required a combination of perseverance and good fortune. With October’s FDA approval, the project entered a new phase, as investment groups and equipment builders began exploring commercialization opportunities.

In the meantime, the WSU team led by Professor Juming Tang continues to optimize the design and prepare FDA filings for additional products. Tang has taught food engineering at WSU since 1995, following similar academic duties at South Dakota State University and Canada’s Acadia University. Since 2001, he has served as director of the Microwave Sterilization Research and Development Consortium, which includes Kraft, Hormel, Rexam Containers and the US Department of Defense. Tang earned an undergraduate degree in mechanical engineering at Central-South University of Technology in Hunan, China, before studying in Canada, receiving a master’s degree at University of Guelph and a PhD in agricultural engineering at the University of Saskatchewan.

FE: Describe the microwave system’s design.

Tang: We use single-mode microwave energy and concepts found in a conventional retort: recirculated water spray in a pressurized vessel and an environment where you raise the temperature close to 250

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