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Journalism of Courage
A new book on the science of tea has sparked online debates among Americans and the British on the best way to prepare the world’s second-most-consumed beverage (after water).
Author of the book ‘Steeped: The Chemistry of Tea’ and Chemistry professor Michelle Francl said in an interview to the UK news outlet Daily Mail on Wednesday (January 24), that a pinch of salt should be added to tea to reduce its slightly bitter taste. The UK’s Cabinet Office and the US Embassy in the UK also joined in on the ‘fight’, with the latter saying in a statement: “We want to ensure the good people of the UK that the unthinkable notion of adding salt to Britain’s national shrink is not official United States policy. And never will be.”
Tea has long been seen as a beloved drink in Britain, ever since it first reached European shores from China in the colonial era. Meanwhile, the US is largely a nation of coffee drinkers, and the differences in preferences – along with the ways of preparing tea – have often been a source of friendly contentions.
Both tea and coffee have a slight bitterness to them (also described as being astringent). This is partially because of the compounds caffeine and tannin. The explanation behind why the salt tip seems to work for some seems to be related to how the human tongue experiences taste. Taste receptors are key cells in this regard.
“Humans perceive taste through thousands of tiny sensory organs called taste buds, which are located mostly on the upper surface of the tongue. Each taste bud contains 50 to 100 taste cells, which contain molecules, known as receptors, that can detect each type of taste—sweet, bitter, sour, salty, or umami (savory). These taste cells then relay this information from the tongue to the brain,” according to Columbia University Irving Medical Center (CUIMC).
CUIMC found in 2017 that signals sent by the tongue’s taste cells prevent the brain from confusing flavours such as bitter and sweet. So apart from the receptors, it is also the signals sent to the brain that affect the perception of taste. When salt and bitter compounds are mixed, according to earlier research, salt can help mask the bitterness. Salt is also used at times in baking, to help enhance the sweetness of an item. But how exactly does salt do this is not very well-known.
Francl said adding a pinch of salt helps because the “sodium ion in salt blocks the chemical mechanism that makes tea taste bitter.” A BBC report noted that her suggestion is not the first. She reportedly got the idea from “eighth century Chinese manuscripts”. “What is new is our understanding of it as chemists,” Francl said.
Many unusual things, according to the new book. Fracl’s work is reportedly a product of three years of research and experimentation. The book explores the more than 100 chemical compounds found in tea and “puts the chemistry to use with advice on how to brew a better cup,” its publisher says.
She says that firstly, the tea cup needs to be short and stout to conserve heat. It should be heated separately to “release more ‘aromatic compounds’”. Loose tea is preferable to teabags because it results in more room for tea leaves to circulate, and this enhances the fragrant compounds. She also discourages using microwaves, seemingly the preferred mode to make tea in the US.
Francl told The Guardian that in case tea bags are being used, they should be large for the same reason. They should be steeped in hot water quickly but with plenty of dunking and squeezing. This helps reduce the sour-tasting tannins (which lend the astringent flavour), created by caffeine dissolving slowly in water.
Finally, warmed milk should be added after pouring the tea to reduce the chance of milk curdling. Another tip was adding a small amount of lemon juice to remove the “scum” that sometimes floats on the surface of the drink, which is formed from chemical elements in the tea and water.
Francl writes in her book’s introductory chapter that “The chemistry of tea is also entwined with more fundamental discoveries in science.”
She recalls the history of how in 1902, Emil Fischer was awarded the second-ever Nobel Prize in Chemistry, “in part for his work on caffeine”. Francl adds: “In 1913, Hungarian chemist George de Hevesy had tea with another young scientist working at Manchester, Henry Moseley. de Hevesy wondered aloud if there was a way to follow the water molecules in the tea through his body… But 20 years later, with the help of Harold Urey’s gift of heavy water and a few dozen goldfish, not to mention liters of distilled urine, de Hevesy would crack the problem. The work would contribute to de Hevesy’s 1943 Nobel Prize in Chemistry for the development of isotopic tracing—a phenomenon that has spawned such innovations as PET scans and methods for mapping ocean currents.”
