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How to detect the cheap filler ingredients in your pricey coffee

Ground coffee can contain adulterants like corn and soybeans.
Reuters/Brendan McDermid
Four down, one to go.
By Michael Silverberg
Published Last updated This article is more than 2 years old.

What exactly is in your cup of coffee? Besides coffee grounds and water, of course, there may be corn, potato flour, soybeans, brown sugar, and other fillers. Coffee ranks alongside olive oil, honey, and milk as one of the most frequently adulterated foods. And as climate change and a coffee-eating fungus wreak havoc on the world’s arabica supply, the tinkering is likely to rise as producers try to maximize profits.

Ground coffee is typically tested by taste, smell, or a gander under a microscope—hardly the level of sophistication you’d expect for the world’s second-most-traded commodity. But researchers in Brazil, one of the world’s top coffee suppliers, have developed a simpler, less error-prone test that can sniff out filler materials by their chemical fingerprints. The test uses liquid chromatography, a process that separates individual components from a mixture and identifies each one according to its chemical content. Comparing carbohydrate profiles, it’s simple to spot adulterants like grains from pure coffee.

“With our test, it is now possible to know with 95% accuracy if coffee is pure or has been tampered with,” says Suzana Lucy Nixdorf, who led the research and is presenting the findings this week at a meeting of the American Chemical Society. If the test is adopted by the industry, expect fewer potato-flour espressos—unless you’re into that sort of thing.

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