If you find that the energizing effect of your morning cup has worn off before the bus arrives, the scientist behind the controversial tip to put salt in tea has an even sweeter tip: try grapefruit.
Michelle Francl, a professor of chemistry at Bryn Mawr College, has a international storm in a teacup last month after suggesting that a pinch of salt would create the perfect brew.
Now she has a tip that’s far less likely to reignite the biggest transatlantic fight over tea since the American Revolution: ways to prolong the pickup. Speaking at an online webinar hosted by the Chemistry World magazine, she revealed that fruits and vegetables can prolong or shorten the caffeine rush.
“If you eat a lot of grapefruit, you can increase the amount of time the caffeine stays in the system,” Francl said. “And if you add cabbage, broccoli and Brussels sprouts to your diet, you can clear caffeine faster.”
She said the response to the advice given in her book Steeped: the Chemistry of Tea left her “overwhelmed” – especially the diplomatic interventions that followed – and that the American approach to making a brew was not to her taste.
Her advice caused an outcry, and led the American embassy to London to post on X that “the unthinkable idea of adding salt to Britain’s national drink is not official policy of the United States. And never will be.” However, the otherwise reassuring post ended: “The US Embassy will continue to make tea the right way – by microwaving it.”
Francl has a problem with the American habit of using a microwave oven for their brew. She said the approach promotes the formation of a cloudy material, known as tea foamcomposed of organic matter with calcium and magnesium carbonates.
“This happens when you microwave because you bring things to a boil so quickly, you don’t remove the oxygen and the carbon dioxide. So you have more carbonates in the water and oxygen also promotes the development of the organic matter that leads to this floating stuff.”
Francl said consternation over a previous comment — that milk should be heated — was somewhat of a misunderstanding, noting that she didn’t mean it should be heated.
“But really cold milk from the fridge poured into hot tea can actually curdle,” she said.
Francl said the size and material of tea bags mattered, but not their shape, while it was important to warm a teapot before use to ensure water did not cool when added.
“At 60C, the total caffeine extracted is about half that of 90C,” she said. “[If] the water [you are] used to make your tea isn’t hot enough, you’re not getting the caffeine dose you think you’re getting.”
For those who like a calming cuppa, Francl said earl gray may be best because it has higher levels of a substance called linalool because of the citrus oil it contains.
“It appears that linalool activates the same pain relief pathways as opioids,” Francl said. Inhalation of the aroma has been shown to reduce pain perception in mice and anxiety in humans.
“Earl gray tea with that distinctive flavor is something that can reduce anxiety in people. So when my husband drinks that cup of tea before his departmental meeting, he is on to something.”
Scientists have revealed there is another key ingredient to the perfect tasting cup: microbes.
In the journal Current Biologyresearchers reported that different varieties of tea are associated with different soil microbes, and that varieties associated with microbes involved in nitrogen metabolism contain higher levels of the amino acid theanine – a substance that forms the flavor of the drink.
“Our results show that the flavors of tea can be influenced by soil microbes, as we showed that the microbes influence the level of theanine,” said Zhenbiao Yang, a co-author from Fujian Agriculture and Forestry University in China.
“However, the microbes are unlikely to have an impact on the type of tea, which is mostly determined by cultivars and processing procedures.”
