The film on the tea can be an indicator of its taste

(ORDO NEWS) — It turned out that the Eastern tradition of adding salt to tea can really improve its taste, as well as the thin film that sometimes forms on the cooled drink.

The earliest monograph on tea is a series of scrolls called Cha Jing (Tea Canon) dating back to 762 BC. The author of the treatise, the Chinese poet and writer Lu Yu, describes the process of making tea: “During the first boil, add the amount of salt corresponding to the amount of water to harmonize the taste.”

The same practices of adding salt to tea are known in Mongolian, Tibetan, Kazakh and other oriental traditions. They seem strange to Europeans, but scientists from Switzerland have shown that the salt in tea can actually improve its taste.

Many people noticed a not very appetizing thin film on a little standing tea. Its surface has a metallic luster, and if the integrity is broken, “cracks” are formed, reminiscent of sea ice. The formation of the film is influenced by the hardness and acidity of the water, the presence or absence of sugar or milk in the tea, the concentration of the drink and the brewing temperature.

But still, few people know why such a film is formed.

Moreover, science became aware of this relatively recently: studies of the 1990s showed that the main role in the formation of a film is played by calcium carbonate contained in water and reacting with a drink. Previously, it was believed that the film was the result of the residual wax coating of the tea leaves.

Researchers from the Swiss Higher Technical School, whose work is published in Physics of Fluids, have taken up further study of this seemingly unremarkable phenomenon.

The scientists evaluated the mechanical properties of the tea film using interfacial rheometry, focusing on its chemical composition and thickness. In addition, they studied the rheological properties of the film by adding various concentrations of calcium carbonate to tea.

As a result, it was found that the films contain oxidized tea polyphenols, calcium carbonate, and other salts. And if you brew tea in perfectly clean, filtered water, it will not have a film, and the drink itself will acquire a different taste – less intense and more bitter.


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