Keeping chocolate milk smooth, stable without carrageenan

High-pressure jet processing of food is a completely new concept, Harte pointed out, and he has been experimenting with the idea for about six years at Penn State. His work on the technology in a pilot plant in the Rodney A. Erickson Food Science Building is unique because it uses an intensifier pump the size of a subcompact car to spray milk through a diamond or sapphire nozzle. The liquid exits the nozzle as a jet of fine droplets that collide with the air, forming an aerosol.

“The equipment that we use for making these chocolate milks is not equipment that you find in the food industry — you would normally find it in an engineering services shop,” Harte said. “This equipment is used for cutting metals. It’s a water jet instrument that is used for cutting tough materials such as marble or stainless steel. We are using it in a completely different application.”

Harte bought the equipment with funds from a National Institutes of Health grant a decade ago when he was a faculty member at the University of Tennessee and had it shipped to the University Park campus when he came to Penn State. “You won’t find this type of instrument in any university food science department in the U.S.,” he said. “And I don’t know of any in other parts of the world, either.”

To appreciate the pressure developed by the pump that processes the chocolate milk, Harte offers this comparison: At the bottom of the Mariana Trench — the deepest point in any ocean — the pressure is 100 megapascals. “We are applying five times that pressure, 500 megapascals,” he said. “The liquid, as it leaves the orifice, is moving at Mach 3 — three times the speed of sound.”

Also contributing to the study were Michelle Tran and Grace Voronin, graduate students in food science; Robert Roberts, professor and head of food science; John Coupland, professor of food science; and Greg Ziegler, professor of food science.

The U.S. Department of Agriculture’s National Institute of Food and Agriculture and the National Dairy Council partially funded this research.


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