Dirt, corn and twigs: A test reveals hidden coffee ingredients that aren’t necessarily good for you. (Claudio Baldini/Photographergallery.org)

Cream and sugar may not be the only additives in your morning cup of coffee. Tough growing conditions and rising demand are leading some coffee producers to mix in wheat, soybean, brown sugar, rye, barley, acai seeds, corn, twigs and even dirt.

The filler ingredients are natural and don’t pose health risks for most people. But these additives could be a serious problem for people with soy or wheat allergies, said Suzana Lucy Nixdorf, a researcher at Universidade Estadual de Londrina in Brazil.

That’s why Nixdorf developed a chemical test that can spot the difference between a batch of pure coffee grounds and a batch with unwanted ingredients. [10 Things You Need to Know About Coffee]

According to a 2013 report from the National Coffee Association, 83 percent of Americans drink coffee, up from 78 percent in 2012, and 63 percent said they drink it daily. The health effects of coffee are not totally clear, though studies suggest it may reduce the risk of developing Type 2 diabetes, some cancers and cognitive decline.

As the demand for coffee increases, high temperatures, drought and a plant disease known as coffee rust are devastating Arabica coffee trees, which produce one of the most popular kinds of coffee bean and are grown in high-altitude farms in Central and South America.

Brazil, the world’s leading producer of coffee, usually cranks out about 55 million 132-pound bags each year. But a drought that hit the country in January and lasted through March means that Brazil’s coffee growers may produce about 10 million fewer bags this year, according to one estimate. That difference translates to about 42 billion cups of coffee lost.

That doesn’t mean that caffeine addicts and coffee lovers should start hoarding coffee beans. Producers will probably be able to keep up with demand, but they may have to rely more on lower-quality coffee, Gleidson Patto, a coffee cost analyst , told National Geographic News.

These trends will eventually drive up the price of coffee and are already encouraging “coffee counterfeiting,” experts say, because fillers can make supplies of pure ground coffee last longer and boost profits.

“Less coffee makes prices rise,” Nixdorf said. “You pay for coffee, but you aren’t really getting coffee. That’s the problem.”

How to spot coffee fraud

One way to detect counterfeit coffee is to put the grounds under a microscope, Nixdorf said. But after the beans are roasted and ground, it may be close to impossible to spot any twigs, berries or even dirt that blend in with the dark grounds. Nixdorf said because it is common for Brazilian growers to produce very dark roasts, filler ingredients can blend in better.

Counterfeit coffee also can be identified by taste. For example, coffee grounds mixed with corn will produce sweeter coffee, but the subtle flavor change can be hard to detect, Nixdorf said.

Nixdorf invented a test that analyzes the chemical composition of coffee. She uses liquid chromatography, a process that creates a unique stain for each ingredient. First, brewed coffee is sent through a pressurized pump and a special paper filter. Each ingredient interacts differently with the filter and flows through it at different rates. The ingredients are separated by the length and color of the stain they leave behind. The filler ingredients have different sugar levels than the natural compounds in coffee, and they leave behind distinct stains. Nixdorf said the test can tell if filler ingredients are mixed into coffee grounds with 95 percent accuracy.

For now, the chromatography test can be done only in a lab. Nixdorf recommended that consumers grind their own coffee beans or buy ground coffee from reliable brands and trusted shops.

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