Why does green tea taste bitter?
What are the properties that provide this peculiar flavor, unique to common tea?
Originally from China and Japan, this ancient drink began to be consumed in the year 2,700 BC and became a fundamental part of the culture of many Asian countries.
However, it was only in the mid-1920s, when its chemical composition began to be studied and analyzed in detail, that it was possible to understand, among other things, where this bitter taste comes from.
The scientist responsible for this discovery is named Michiyo Tsujimura. Thanks to her curiosity and incredible ability to process tea leaves for analysis, the scientist concluded that the tea contains healing and beneficial elements for health.
But how did she manage to arrive at this discovery in a scientific world hitherto dominated by men?
Pioneer of science in Japan
Michiyo Tsujimura was born in 1888 in what is now the Japanese city of Okegawa, in Saitama District. She studied at Tokyo Normal School for Women, where she graduated in 1909.
She later joined the Department of Biochemical Sciences at Tokyo Higher School for Women. That’s when she discovered her interest in scientific research, which, until then, was mainly conducted by men.
Tsujimura met other women at the beginning of her career, such as Kono Yasui, a renowned cell biologist and biochemist, who would become the first Japanese woman to obtain a doctoral degree in science, deeply inspiring Tsujimura.
After graduating in 1917, Tsujimura devoted herself to teaching science at the country’s pioneering girls’ schools. But her huge interest in learning led her to move forward, entering the Imperial University of Hokkaido, Japan, which did not accept women as students.
Therefore, she joined as an assistant at the Laboratory of Nutrition and Food in the Department of Agricultural Chemistry, without receiving remuneration for her work.
At this post, Tsujimura devoted himself to studying silkworms and their nutrition. And so, little by little, it began to be recognized.
C vitamin
But her real passion wasn’t in silkworms. Two years later, in 1923, Tsujimura joined Riken—the immense and respected Japanese natural science research institute.
She worked in the laboratory that studied chemistry and nutrition in agriculture, alongside the famous scientist Umetaro Suzuki, who successfully discovered and extracted vitamin B1 from rice bran.
Tsujimura’s attention was especially drawn to green tea, which was (and still is) a very popular drink in Japan, China and other Asian countries. It was unbelievable that it had been so little studied.
Therefore, in 1924, thanks to a joint research with his colleague Seitaro Miura, Tsujimura discovered a strong presence of vitamin C in the leaves used to prepare the infusion.
According to the University of Ochanomizu in Japan, this discovery caused a huge increase in interest in green tea in the West, particularly in the United States — and, with that, the beverage’s exports from Japan to North America also increased.
PhD in agriculture
But Tsujimura’s research would not end there.
In 1929, the scientist managed to isolate and extract a flavonoid called catechin, a powerful natural oxidant that, among other functions, helps prevent cell damage and is responsible for the bitter taste of tea.
The following year, Tsujimura was able to extract catechin in the form of crystals — as well as tannin, another antioxidant component of green tea.
The University of Ochanomizu says this research required “a lot of patience” because it took repeatedly boiling a large amount of green tea to get a small amount of crystals. But the scientist knew that patience was a fundamental principle of her work.
“Chemistry is not for people who want to see results within a certain time frame,” she once said.
Afterwards, Tsujimura published his thesis with the two discoveries (vitamin C and catechin), entitled “On the chemical components of green tea”. With her, the scientist became the first woman to obtain a doctoral degree in agriculture in Japan, in 1932.
But her interest in green tea continued, and in 1934 she managed to isolate galocatechin, another flavonoid compound that is beneficial to health.
In 1935, Tsujimura patented his method of extracting vitamin C crystals from plants.
Currently, this procedure is used on a large scale throughout the world and the crystals are present in pharmaceutical form, in oral nutritional supplements.
A decade later, the scientist was appointed a professor at the University of Ochanomizu, where she would become the first woman to hold the position of dean of the Faculty of Home Economics.
After her retirement from Ochanomizu University in 1955, Tsujimura taught at Jissen Women’s University until the mid-1960s.
A year before her death, in 1968, the scientist examined her research career and told her students: “My research work was full of difficulties, but it was very pleasant. Having no regrets in life was my supreme happiness. “
Until his last days, Tsujimura used to go for long walks with his dog. She died in Toyohashi, Japan, on June 1, 1969, aged 81 years.
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