After a lovely dinner and as dessert is about to be served, nothing sounds so enticing as being asked if you would like any “aqueous infusions prepared from dried plants.”
And the authors of these poetic words continue with an equally inspiring endorsement of tea, with its “desirable physiologic activities and potential health benefits.”
But looking past scientific speak, this 2011 study of plant DNA identifications for commercial teas yields some fascinating info, and I want to thank Mike Loab of Leaf House Tea for bringing this work to my attention.
Researchers Mark Stoeckle and team tested DNA barcoding, which uses a short sequence of DNA, as a way to determine whether the plant products that are in a given tea match the ingredients listed on the label.
After all, it’s sometimes hard to tell what you have when you just look at tea or herbal leaves, as users of Reddit know well—with many people sending in photos of various dried plants and asking if anyone knows what on earth the stuff is! And even when you might think it’s definitely A, another person will argue that it’s surely B.
I’ve looked at identification studies before, mostly those seeking to determine whether a particular tea actually comes from the country that the seller claims (see post Why Fingerprinting Tea Is a Good Idea).
I’ve also previously looked at adulteration of tea (see post A Royal Tea: Victorian Earl Grey), which is not confined to today. Back in 1853, Robert Fortune noted that Prussian blue and gypsum made tea leaves “uniform and pretty,” fetching better prices in the English and American markets. He also calculated that “in every hundred pounds of coloured green tea consumed in England or America, the consumer actually drinks more than half a pound of Prussian blue and gypsum!” And even after tea reached England, other plant material might make their way into tea.
But this study by Stoeckle et al. has a bit of a twist that I didn’t expect.
The scientists evaluated 146 teas that all together listed 82 plant names. Half of the teas were Camellia sinensis (true tea) and half were herbal teas (tisanes).
They isolated and sequenced DNA from each tea, then matched them to existing databases. Of the 146 teas, 58% of them matched the listed ingredients. Of course some may not have matched because the databases were incomplete, differences within a species hadn’t yet been documented, or there simply was an error somewhere.
But other reasons for a product not matching its label included contamination—with different plants, with weeds, and, disconcertingly, even with non-food plants.
It stands to reason that when herbs are harvested, other plants could easily find their way into the mix. Or that a similar-looking or more-flavorful herb might be blended in. Or even a prettier herb, such as flower petals.
In this study, seven herbal teas were found to include chamomile although that was not a listed ingredient.
Similarly, it seems feasible that a subpar tea just might have some other, cheaper, plant material added in to stretch the tea out, bring down production cost, and so on.
But four herbal blends also contained Camellia sinensis leaves, which were not listed on their label!
I was not expecting that, and people who are extremely sensitive to caffeine probably won’t be happy to learn that this is a possibility!
While the researchers point out that processing equipment could account for some of this contamination, they also make the point that:
the finding of unlisted chamomile (M. recutita) or tea plant (C. sinensis) in multiple products suggests the possibility of addition or substitute to improve taste, appearance, or for economic reasons. (Stoeckle et al. 2011)
Such results strengthen the argument for buying tea that has been vetted by an independent facility, and give researchers good reason for continuing work into DNA fingerprinting so that we consumers can be confident that what we get is exactly what we’ve been told we’re getting.
And if your caffeine-free herbal blend seems to be keeping you awake at night, maybe the tea really is to blame.
–Fortune, R. Tea Countries of China and the British Tea Plantations in the Himalaya, John Murray, London, 1853.
–Stoeckle, M. Y. et al., “Commercial teas highlight plant DNA barcode identification successes and obstacles,” Scientific Reports 1(42), 7/21/2011.