60-Second Science

Student Researchers Find Secret Tea Ingredients

Three NYC high school students did DNA analyses of various teas and spotted sequences belonging to lots of flora that weren't listed on the label. Cynthia Graber reports

After water, tea is the world’s most popular drink. Now three New York City high school students [Catherine Gamble, Rohan Kirpekar and Grace Young] have discovered what may be a brewing scandal. Because they found stuff in lots of teas that shouldn’t be there.

The students were guided by professional researchers as they worked their way through 70 teas and 60 herbal varieties. The material tested came from 33 companies and originated in 17 countries.

The high schoolers extracted and amplified the tea DNA and then sent it to a sequencing facility. They then compared the sequences they got back with known sequences listed in the GenBank database maintained by the U.S. National Library of Medicine.

The junior scientists found that four percent of the straight teas contained additional plant material. And more than a third of the herbal products included unlisted ingredients – such as the weeds bluegrass and white goosefoot. Four of the herbal mixes contained relatives of parsley. And seven had unlisted chamomile.

The research was published in the Nature journal Scientific Reports. [Mark Stoeckle et al., "Commercial Teas Highlight Plant DNA Barcode Identification Successes and Obstacles"]

The effort shows that it’s possible to cheaply identify food ingredients and do quality control. And all that chamomile may represent an attempt to keep us calm about impurities.

—Cynthia Graber

[The above text is a transcript of this podcast.]

[Scientific American is part of the Nature Publishing Group.]

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