Process Improved For Gauging Temperature Of Food Before Packaging

July 15, 1997

CHAMPAIGN, Ill. - A magnetic particle about 2 millimeters in diameter could improve food processing and lead to more nutritional products, University of Illinois researchers say.

The particle can be inserted temporarily in solid food suspended in liquid, thereby allowing aseptic food processors to measure the interior temperature of the food. In current aseptic processing, which preserves a product for stable and long-lasting packaging, a drink is thermally treated separately from its container as the drink is pumped through a pipeline. The process is considered superior to canning.

However, the process hasn't worked with foods such as peas, beans and stews prepared in liquid because there has been no way to make certain the solid has been heated sufficiently to kill bacteria. Current processes for canning can overheat a product, reducing its quality and nutritional value.

"Aseptic processing has been used for years for liquid foods, but no one has been able to safely process foods with solids mixed in with the liquid," said Bruce Litchfield, a professor of agricultural engineering at the U. of I. "The technique for processing food is passing it through a heat exchanger, and there is no way to have a temperature sensor go through. With liquid, you put a sensor into the pipeline, but solids heat more slowly, and you don't know if that chunk of potato, for instance, has been adequately heated."

The solution may be in the use of magnetic materials whose properties are temperature dependent, said Ken Ghiron, a postdoctoral scientist who is working with Litchfield. Ghiron is refining small ferromagnetic balls that acts as sensors when inserted into solid food. When the food passes through a magnetic field, the balls become magnetized, producing voltage that allows for accurate measurement of temperature within the solid. The balls are easily removed at the end of processing.

Ghiron described his technique at the seventh International Congress on Engineering and Food, held in Brighton, England, in April. A paper on his presentation was published in the proceedings of the event. A Chicago food manufacturer has agreed to test a prototype of the invention on its aseptic processing line later this year. The U. of I. has filed for U.S. and international patents.

"It has the potential to allow processors to package and deliver foods that are higher in nutritional value and flavor," Ghiron said. "This process uses less energy and allows for the use of lighter packages that are easier to ship. Hopefully, it will put better food on people's tables."

Litchfield previously had worked with other U. of I. researchers in creating a method to measure interior temperatures of food using magnetic resonance imaging. "The MRI results had been very effective, but using MRI is very expensive. This method is very inexpensive."

The research is funded by grants from the Illinois Council on Food and Agricultural Research, an industry consortium of companies known as the Center for Aseptic Processing and Packaging, and the Midwest Advanced Food Manufacturing Alliance.

University of Illinois at Urbana-Champaign

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