Health of Tea
Over the past millennia, tea has served its main purpose to people from
every walk of life, those from high society and those from the working class,
and that is, to provide its various health-conducive medicinal effects. Most
research done regarding tea has focused on green tea and black tea, but there
is this professor Lin Jen-kuen from the National Taiwan University Hospital and
his team working on tea and its preventive attributes against cancer. They
found a close relationship between the amounts of polyphenols taken in and
cancer inhibition. His team must be the only team on earth that has devoted
their time to studying Baozhung tea and Oolong tea.
The medicinal and health-conducive properties from tea are mostly physiological and can be found in polyphenols, or to be more exact, in catechins. The following are the catechin-related medicinal effects that have been experimented on the human body and proved effective.
The medicinal and health-conducive properties from tea are mostly physiological and can be found in polyphenols, or to be more exact, in catechins. The following are the catechin-related medicinal effects that have been experimented on the human body and proved effective.
1. To function as anti-oxidants, to remove the free radicals
and to slow down the aging process.
The polyphenols found in any tea have been found to have
powerful anti-oxidant effects, to be able to temper the free radicals produced
from all over the body, and to curb the fats from oxidation and to alleviate
allergic reactions. Due to their high metabolic rate in the body, to better
make use of their various healthful effects, one has to consume them regularly
to maintain the right consistency in the environment for antioxidants.
2. To curb hypertension
Three months into a daily intake of 500 milligrams of
catechin, any healthy person will find that his systolic and diastolic pressure
have both been markedly reduced after a meal.
3. To reduce blood sugar
Catechin inhibits starch intake and sucrase, and it is
believed that catechin serves as an inhibitor of the rising blood sugar level
and helps with weight reduction.
4. To prevent dental caries
The fluoride in tea is believed to work against dental
caries, to be resistant to the corrosive property against the tooth enamel. Catechin
also serves as a powerful agent against streptococcus mutans. Clinically it has
been proved that catechin can remarkably reduce dental plaque and the
possibility of periodontitis without working negatively against the other
microorganisms in the mouth.
5. To have anti-carcinogenic effects
Professor Lin Jen-kuen from NTUH and his team found that
the amounts of polyphenols have a lot to do with the inhibition of cancer. In
addition, tea grown in the mountains mostly contains more polyphenols than tea
in the plains. One factor is the slower growth for tea trees in the mountains,
with the result that polyphenols can take their time in their formation. Also,
polyphenols like EGCG (Epigallocatechin-3-gallate) and TF-3 have inhibitive
effects on such reactive oxygen species as generated by xanthine oxidase.
6. To soothe the intestines and combat bacteria
Modern-day research has pointed out the inhibitive
effects catechins have on such disease-inducing bacteria as botulinum toxin;
however, catechins do not interfere with the multiplication of useful bacteria
(lactic acid bacteria) in the intestines. In a word, catechins have nothing but
benefits for the functions of the intestines.
The Chemistry of Tea
The chemicals in tea can be a maze of variety, generally categorized into
fresh leaves, tea and tea liquid. The chemicals in fresh leaves vary from
species to species, having to do with their position in the tea tree, the
environment and ways of cultivation. The tea-making process exposes tea leaves
to oxidation, decomposition, and aggregation of different degrees. The tea
liquid is the water-soluble part from tea and dictates the quality of the tea.
（% of dried tea）
Content |
Fresh Tea
|
Black Tea
|
Liquid of Black Tea
|
protein
|
15
|
15
|
few
|
cellulose
|
30
|
30
|
0.0
|
pigments
|
5
|
5
|
few
|
caffeine
|
4
|
4
|
3.2
|
polyphenols, prototype
|
30
|
5
|
4.5
|
polyphenols, oxidized
|
0
|
25
|
15.0
|
free amino acids
|
4
|
4
|
3.5
|
ash
|
5
|
5
|
4.5
|
carbohydrate
|
7
|
7
|
4.0
|
flammable materials
|
0.01
|
0.01
|
0.01
|
Resource：Sanderson (1972)
Polyphenols
The biggest portion of solubles in tea leaves are polyphenols, accounting
for 30 percent of the weight of dry goods, with 80 percent of that being
catechin, the key to the color, taste, and quality of tea liquid.
Theaflavins and thearugigins are fermented (oxidized) byproducts generated by catechin in the tea-making process. These materials explain the yellow, red, brown colors of fermented teas. The amount of catechin has most to do with the tea-making process (fermented or not), and yet other factors also have to be taken into account such as the season it is, the species, the position in the tree and the ways of cultivation.
Tea making is in a sense the control of reaction of catechin to oxidation in the course of fermentation, which results in the unique features of tea. Catechin plays a key role in the fermentation, the most essential ingredient to the tea leaf.
Theaflavins and thearugigins are fermented (oxidized) byproducts generated by catechin in the tea-making process. These materials explain the yellow, red, brown colors of fermented teas. The amount of catechin has most to do with the tea-making process (fermented or not), and yet other factors also have to be taken into account such as the season it is, the species, the position in the tree and the ways of cultivation.
Tea making is in a sense the control of reaction of catechin to oxidation in the course of fermentation, which results in the unique features of tea. Catechin plays a key role in the fermentation, the most essential ingredient to the tea leaf.
Caffeine
Caffeine is also called theine. Caffeine weighs 3 to 4 percent of the dry
goods, bitter and a powerful alkaloid, a stimulant to the central nervous
system, and serves to alleviate exhaustion. It is believed that the combination
of catechin and caffeine acts in a way to cushion the impact of caffeine on the
body. Fresh leaves in different seasons contain different amounts of catechin.
In the tea-making process and in storage, caffeine has but minor changes, which
means caffeine functions as a very stable agent in tea leaves.
Free Amino Acids
There are more than 20 free amino acids in tea leaves, accounting for 2 to
4 percent the weight of the dry goods, with theanine claiming the highest
percentage, most of which can be found in the stems. In the leaves, mostly
theanine is found in the tender one-leaf-and-one-bud part, decreasing in
proportion to its maturity.
Besides having a lot to do with the taste of the tea liquid, free amino acids also serve as an aroma precursor in tea leaves, and in the roasting process the Maillard reaction between the amino acids and the reducing sugars brings out the aroma in tea leaves.
Besides having a lot to do with the taste of the tea liquid, free amino acids also serve as an aroma precursor in tea leaves, and in the roasting process the Maillard reaction between the amino acids and the reducing sugars brings out the aroma in tea leaves.
Pigments
In fresh leaves are found lots of pigments, most of which are green
chlorophylls and light coral carotenoids, both of them fat-soluble, not
water-soluble. The color of carotenoids emerges only when chlorophylls decrease
due to damage. It has been found that in the tea-making process some
carotenoids add to the aroma of tea leaves, a reason why they are considered to
be an aroma precursor.
Aroma from Flammable Materials
The insipid and indefinite aroma explains the popularity of tea. Both the
quality and the processing of the tea leaves contribute to this divine aroma.
The flammables in the fresh leaves account for the aroma, alcohols, aldehydes,
ketones, esters, and nitrogen compounds all playing their respective parts.
Alcohol compounds are the key player in fresh leaves. Those low-carbon and
low-fat compounds give off a vanilla-like smell, while the aromatic compounds
and alkene compounds help with the fragrance of flowers.
Some fermented tea goes through only 20 to 30 percent the fermenting process
of black tea, giving off a light floral fragrance. According to research
conducted in Japan, in Baoczhung tea are found huge amounts of nerolidol,
jasmine lactone, methyl jasmonate and benzyl cyanide among others. Since the
bigger part of the jasmine flower is composed of jasmine lactone and methyl
jasmonate, the two ingredients also found in Baozhung tea, it is only
understandable why the tea gives off the exhilarating aroma of the jasmine
flower.
Carbohydrate
The tea leaf is mainly composed of cellulose, most of which is not
water-soluble so it will not end up in the tea liquid, nor will it suffer major
changes during the tea-making process. Carbohydrates are a rare element in tea
leaves, with their amounts not much different from one to the other, depending
much on the environment and the tea-making process. A high percentage of pectin
can be found, so they have a way of influencing the consistency of the tea
liquid. Starch is rare, except in the case of old leaves.
( source of information: Tea in Taiwan; The Holy Bible
for Tea in Taiwan)
