Tea World

Lesson 3

Antioxidants in Tea

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You all know that all tea comes from the same plant, Camellia sinensis.Only the differences in processing yield the various  types of tea  such as black tea, green tea, oolong tea, white tea etc. You will learn how to process different types of tea in the Lesson, “Tea Processing”. The antioxidants present in tea are a group called flavanoids.

Catechins and Theaflavins, Green and Black Tea

Catechins are a class of flavanoids found in tea. The six main catechins found in green tea are catechin, gallocatechin (GC), epicatechin (EC),epigallcatechin (EGC), epicatechingallate (EGCG) and the most important, epigallocatechin gallate (EGCg or EGCG).

In black tea, and oolong tea, catechins are oxidised during fermentation of manufacture and transformed to compounds with tanning properties. The oxidised polyphenols in made tea are divided into two groups: thearubigin (TR) partly polymeric pro-anthocyanidins and impart colour to the tea infusions,the second group of compounds are theflavins (TF- theaflavin 3-0-gallate) contribute to the briskness of the tea infusions. The theaflavins – theaflavin (TF1), theaflavin-3-gallate (TF2A), theaflavin-3′-gallate (TF2B) and theaflavin-3,3-digallate (TF3) are formed during the fermentation (oxidation) process. As with catechins, these theaflavins also possess antioxidant properties.

Green tea contains very high levels of polyphenols, mainly catechins. In green tea, they are present in significant quantities. The polyphenols in green tea which have powerful anti-oxidant properties   enhance immunity by preventing or slowing down the oxidative damage to our body. They protect our cells and tissues from oxidative stress by scavenging on free radicals and reactive oxygen species (ROS) that are responsible for heart disease, diabetes, cancer, hypertension, etc.

The key constituents of green tea provide many health benefits. Studies of MRIs have shown that people who drink green tea had greater activity in the areas of the brain affected by Alzheimer’s disease.

Both green and black tea are good for health. They contain different types (and levels) of polyphenols as you can see from the table below:

Green tea Black Tea
  • Non-fermented
  •  It contains
    •  Catechins – 80-90%
    • Flavonols – <10% of total    flavonoid.
The infused leaf is green, and the liquor is mild, pale green or lemon-yellow
  • Fermented 
  • It contains
    • Catechins – 20-30%
    • Flavonoids-60-70% (Theaflavins–10%, Thearubigins–50-60%)

 The infused leaf has a dark-brownish colour and a sweet aroma

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