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What Is Green Tea, Anyway?
First things first: The word “tea” is only
used correctly when it refers to leaves taken from the Camellia sinensis bush.
And that means that herbal teas really aren’t tea – only green, black
and oolong tea are the “real thing.” That said, the way the Camellia
sinensis leaves are processed will determine which of these three
choices the end product becomes.
To make black tea, the freshly picked tea leaves
must undergo a process called oxidation. Oxidation occurs when an enzyme
in the tea leaf called polyphenol oxidase is brought into contact
with the air. To do this, the leaves are left in the sun for 18-24 hours
to wither and dry; then they’re broken up to encourage further
oxidation. Steaming, pan-firing or roasting the leaves stops the
oxidation process, after which they are rolled, twisted and dried.
Making oolong tea involves a similar process, although the leaves are
withered for a shorter period, which produces a partially-oxidized leaf.
But for green tea, the leaf isn’t withered or broken at all – in fact,
just the opposite! The tea leaves are steamed almost immediately after
picking in order to stop the oxidation process, after which they
are rolled and dried.
The health benefits of the resulting tea will
largely be determined by whether or not the tea leaf has been oxidized.
That’s because the fresh tea leaf contains large amounts of
catechins
(pronounced “CAT-i-kins”), which are the powerful disease fighters and
potent antioxidants that give green tea its health-enhancing abilities.
But when exposed to air and polyphenol oxidase, the catechins change
into completely different compounds called theaflavins and
thearubigens.
The theaflavins and thearubigens, which give black tea its distinctive
taste, aroma and dark color, do have some health benefits, but
not the same wide-ranging antioxidant and disease-fighting prowess seen
in the catechins.
So in green tea manufacturing, it’s extremely
important to rush the freshly picked leaves from the field to the
manufacturing plant, being careful not to break or bruise them. There,
the leaves are steamed or pan-fired immediately to inactivate the
polyphenol oxidase. Afterwards, it’s safe to roll, twist, dry and
package the leaves without worrying about obliterating the catechins.
Yet even after the manufacturing process has been completed, green tea
catechins can be destroyed if exposed to oxygen for too long. That’s why
you should always keep your green tea in an air-tight container, even if
it’s already in tea bag form. Remember: oxygen is the catechins’ worst
enemy!
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Nadine Taylor, M.S., R.D. presents
GreenTeaLibrary.com,
the most comprehensive collection of scientific information
describing the health benefits of green tea.
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