People have been adulterating coffee for hundreds of years, sometimes openly (think Cafe du Monde and other chicory-laced coffee) and sometimes surreptitiously (in the late 19th century, fraudsters added everything from dirt and dog biscuits to lead and cyanide to coffee).
But we're past those dark times right? Not exactly. A 2012 study in the Journal of Food Science found that coffee is one of the top 7 adulterated foods (along with olive oil, milk, honey, and orange and apple juice, and saffron). Unscrupulous coffee vendors mix in corn, soybean, potato flour, and brown sugar, among other additives, Michael Silverberg writes at Quartz. And the usual coffee-purity tests are unexpectedly primitive — largely taste and smell.
Researchers in Brazil, the world's largest coffee producer, have come up with a new test to detect impurities in ground coffee. The procedure, presented at the American Chemical Society's upcoming meeting, uses liquid chromatography and promises to detect additives quickly and with 95 percent accuracy. (The National Coffee Association says the warnings about additives are vastly overblown.) So if this test takes off, great. But you could avoid the risk almost entirely by buying whole coffee beans and grinding them yourself.