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High school project with DNA barcoding reveals what else is in your tea

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Unlisted Ingredients  in Teas and Herbal Brews Revealed in 

DNA Tests by High School Students

New-to-science genetic differences found in teas from India, China;

Research required just $5,000 in equipment atop dining room table; Presenting: 1st DNA portrait of tea family – world’s most popular beverage 


Take a second look at your iced or steaming tea. Guided by scientific experts, three New York City high school students using tabletop DNA technologies found several herbal brews and a few brands of tea contain ingredients unlisted on the manufacturers’ package.

The teen sleuths also demonstrated new-to-science genetic variation between broad-leaf teas from exported from India versus small-leaf teas exported from China.

Guided by DNA “barcoding” experts at The Rockefeller University, an ethno-botanist at Tufts University and a molecular botany expert at The New York Botanical Garden, co-authors Catherine Gamble, 18, and Rohan Kirpekar, 18, and Grace Young, 15, of Trinity School, Manhattan, published their findings today in the Nature journal Scientific Reports.

The results are detailed as well online at http://phe.rockefeller.edu/barcode/teabol2011.html and a short video of the students describing the project is available at http://www.urbanbarcodeproject.org/index2.html 

The unlisted ingredients included weeds such as annual bluegrass and herbal plants such as chamomile. The surprise ingredients are mostly harmless but could affect a tiny minority of consumers with acute allergies.  

Three (4%) of the 70 tea products tested and 21 (35%) of 60 herbal products had unlisted ingredients.

For example, DNA testing showed that an herbal infusion labelled “St. John’s wort” (Hypericum perforatum; EOL page  www.eol.org/pages/584888  ) included material from a fern in genus Terpischore. 

A DNA “barcode” obtained from another herbal tea labelled “ginger root, linden, lemon peel, blackberry leaves, and lemongrass” matched annual bluegrass (Poa annua; www.eol.org/pages/1114594 ), a common weed unrelated to lemongrass. Four herbal infusions yielded sequences identical or nearly identical to the tea plant, C. sinensis (www.eol.org/pages/482447) but none listed “tea” as an ingredient. 

The most common non-label ingredient, found in seven herbal products, was chamomile (Matricaria recutita  (www.eol.org/pages/873076 ).

Four products yielded barcodes of plants closely matching parsley, but none listed ingredients in that plant family.

Other unlisted ingredients included common weeds – white goosefoot (Chenopodium album www.eol.org/pages/587522 ) and red bartsia (Odontites vernus www.eol.org/pages/486640), a garden flower – lantana (Lantana spp.), an ornamental tree – Taiwanese cheesewood (Pittosporum pentandrum); and herbal plants such as alfalfa (Medicago sativa), lemon balm (Melissa officinalis), heal-all (Prunella vulgaris), blackberry (Rubus spp.), and papaya (Carica papaya)