Best Green Tea Chemical Secrets
Revealed By Study

What is your ideal of the best tea to drink? A group of UK scientists thought they might have found the answer for green tea.

Traditionally, tea-makers rely on professional tasters to determine the quality of tea. Higher quality usually means higher price.

Increasingly, scientists are turning to chemical analysis.

Previous studies have found that the quality markers of black tea are theaflavins, thearubigins, catechins and caffeine.

For green tea, they are theanine, catechins and caffeine.

Scientists from the UK Institute of Food Research used a method called high resolution NMR spectroscopy to understand what separates the best green tea from the rest.

The study is large: 191 green teas from 6 different countries were analysed.

According to lead author Dr. Gwenaelle Le Gall, green tea can be harvested in spring, summer and autumn. The first flush in April or May yields the best green tea.

The quality of the tea is assessed through its appearance, flavour and aroma. To quote Dr. Gall:

In general, high quality green tea is described as "delicate" or "sweet".

The chemical constituents depends on different tea types.

The highest quality tea from Japan called Gyokuro is grown under shade and is reported to contain high amino acids but low catechins content.

Sweetness is attributed to amino acids, especially theanine, which has the taste described as "unami" or "brothy", while the catechins and caffeine contribute to the astringency.

...young leaves and a clear brew with a pale green-yellowish tint are indicator of high quality.

The quality of a green tea declines with signs of cloudiness and brown-reddish pigments.

Last but not least, the aroma is also involved in the quality assessment of green tea.

Hence the single most important marker of tea quality is theanine, which gives the best green tea its characteristic sweetness.

Dr. Le Gall went on to explain why the age of tea leaves is important:

Some factors that are not environmental or process related affect the chemical composition of green tea.

The size (age) of the leaves is actually the main criterion for grading green tea, and unlike black tea, green tea quality is directly related to the grading.

In the present [2004] dataset, 38 high quality teas (Longjing or Dragonwell), graded from superfine to 4th grade, were priced from £12-£15 per 50 grams (superfine) to £4-£6 per 50 grams (4th grade).

In comparison, the 77 other Chinese teas ... cost £2.80 per 50 grams (superfine) to £0.80 per 50 grams (4th grade).

The study examined 191 green teas, of which 168 were from China, 7 from Japan, 6 from Indonesia, 5 from India, 3 from Vietnam and 2 from Bangladesh.

The Chinese Longjing teas were the most expensive, along with the Japanese Gyokuro tea.

The scientists found that green teas from different countries have different chemical patterns.

But with only have a small number of non Chinese teas, the scientists were not able to draw any conclusion from the results.

However, they were able to observe clear difference between the Longjing teas and the less expensive teas.

Previous studies have found that important green tea quality markers are theanine, catechins, caffeine and gallic acid.

The scientists discovered Longjing tea contains high levels of these compounds.

There are 4 types of catechins: EGCG (epigallocatechin gallate), ECG (epicatechin gallate), EGC (epigallocatechin) and EC (epicatechin).

Among them, the most potent are EGCG and ECG. A previous study has found that as tea shoots get older, levels of EGCG and ECG reduce, while the levels of EGC and EC increase.

And that's what the scientists found: Longjing tea contains high levels of EGCG and ECG (the most potent), and lower levels of EGC.

Longjing tea also contains higher levels of theogallin, 2-O-(arabinopyranosyl)-myo-inositol, 6 other minor sugar compounds, and lower levels of fatty acids and sucrose.

These compounds may not make the tea tastes better, but they are important quality markers. It's suggested that they are an indication of the maturity of tea shoots.

This is the best green tea paper I have ever read. Dr. Gall knows his tea well. Delicate, sweet-tasting young tea shoots harvested early spring make the best green tea.

The highest grade Longjing tea are made from youngest tea shoots. They contain nutritious compounds such as theanine (a relaxant), EGCG (most potent antioxidant), caffeine (stimulant) and gallic acid (antioxidant).

Are you still looking for the highest quality Longjing tea at the lowest possible price?

How does Dr. Gall's definition of best green tea compare with yours? Tell me about your favourite tea here!

Gwénaëlle Le Gall, Ian J. Colquhoun, and Marianne Defernez (2004). Metabolite Profiling Using 1H NMR Spectroscopy for Quality Assessment of Green Tea, Camellia sinensis (L.). J. Agric. Food Chem., 52 (4), 692 -700, 2004.

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