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A Superior Scoopful
Researchers invent an energy-efficient way to make ice cream
By Lisa Scanlon

Ice cream makers, who are forever dreaming up new flavors, are far less creative when it comes to the machines that actually produce the dessert. The manufacturing devices in today's plants aren't that different from the hand-cranked churn Grandma used, says mechanical-engineering professor Joseph L. Smith Jr., ScD '59. But now, Smith, his colleague John G. Brisson II, and mechanical-engineering graduate student Teresa Baker '03 are creating a process that uses liquid carbon dioxide, saves energy, and results in a creamier-tasting treat.

Ice cream making typically involves two steps: the mix is sent through an externally chilled tube, and then blades within the tube scrape frozen ice cream off the sides, churning it back into the mix. This method, Baker says, is "probably double-processing things" and, therefore, wasting energy. Next, the ice cream, which is partially frozen during this stage, is poured into containers and blast frozen--another energy-intensive process.

The new method proposed by the MIT team blends the liquid ice cream mix into liquid carbon dioxide, a refrigerant. This mixture is sprayed as a fine mist into a metal container, where the carbon dioxide evaporates, freezing the ice cream within milliseconds. Because the process results in a product with very small ice crystals, even low-fat ice cream has a creamy taste. The team completed a prototype ice cream machine last fall and is conducting experiments to gauge the effects of changing variables such as how long the ice cream ingredients and liquid carbon dioxide stay mixed together. There's a long way to go before the method is ready for commercial use, but the rewards of the researchers' hard work will be sweet indeed.