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PNNL researchers cook up ultrasound recipe in new laboratory

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December 14, 2000 Share This!

RICHLAND, Wash. — Researchers at the Department of Energy's Pacific Northwest National Laboratory have cooked up a new way to help food processors solve some sticky, gooey or lumpy problems-add a little ultrasound to the mix.

"Here at home, we've developed ultrasonic measurement techniques to assist DOE at its Hanford site in the transport and processing of nuclear waste, but we've also designed ultrasonic measurement techniques to help the U.S. Customs Service, international border police and security agencies detect contraband associated with weapons of mass destruction," said Dick Pappas, project manager of PNNL's Food Science and Process Measurement Laboratory. "After developing methods to inspect commodities like orange juice and cooking oils for contraband, we saw real possibilities in how ultrasound could be applied directly to the food processing industry."

Earlier this year, ultrasonic sensor capabilities among PNNL's various research areas were consolidated into the Food Science and Process Measurement Laboratory. Today, researchers are putting ultrasound to work on everything from potatoes to pudding. The lab is equipped with an industrial-sized mixer, oven, steam kettle and other standard food processing equipment, all of which are instrumented with ultrasonic sensors.

Additionally, the laboratory contains three flow loops made of plastic piping through which various products can be pumped. Ultrasonic sensors are used to monitor the physical properties of the materials during pumping. The activity mimics the material transport operations that take place during the manufacturing of foodstuffs, chemicals and other consumer products.

"U.S. food processors sell into a very competitive marketplace and they constantly must provide products that meet customer requirements," said Dennis Stiles, manager of PNNL's Agriculture & Food Processing Technology Initiative. In other words, consumers want smooth, not lumpy, pudding and tomato ketchup that is thick, not runny.

"Until now, there has been no non-invasive method available to determine when a product is uniformly consistent in its composition," said Pappas.

Using ultrasonic equipment, companies can test products non-invasively by placing sensors on the outside of the vessels and piping in a product being mixed or transported. For products flowing through a pipe, PNNL has developed a viscosity meter based on ultrasonic Doppler measurements.

"The Doppler measurement is a lot like listening to a train whistle," said Pappas. "Depending on the train's speed and whether the train is moving toward you or away from you, the whistle takes on a different pitch. Similarly, PNNL's ultrasonic Doppler measurement can be used to build a velocity profile for product flowing through a pipe, an invaluable tool for process engineers."

PNNL has developed other acoustic monitoring methods for determining product composition and uniformity. Depending on what is or isn't in the mixing bowl or process tube at the time, or depending on the length of time the product is being mixed, the product exhibits different sound speeds and dissipations. In some cases, particle sizes and concentrations in a product can be measured ultrasonically under process conditions.

Not only are PNNL researchers designing ultrasonic measurement systems for food-specific products, they're looking at other consumer items and chemical products, as well.

For example, shampoo.

"Like most consumer products, the production of shampoo is highly competitive," said Pappas. "By using ultrasonic sensors we might be able to tell that a shampoo, or other product, needs to be mixed 10 minutes instead of 15. If we can help cut down the mixing time we help a company make more product, and profit, by the end of each day."

PNNL is working with several large food processing and consumer product corporations on improving many products including: potatoes, tomato paste, pudding, bread dough, cookie dough, cooking oils, sauces, cake mix, beef, chicken, corn, paper and industrial polymers.

The laboratory works with clients from the pre-proposal/feasibility study phase to the design, prototype and final manufacturing of their specialized piece of ultrasound equipment. Potential clients who would like access to this facility are encouraged to call Walter Weimer, manager of PNNL's Process and Measurement Technology at (509) 375-6922 or e-mail at

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