Tea is enjoyed all over the world, but many

tea lovers do not know that their favorite

black tea and green tea come from the

same plant species: Camellia sinensis.

How can this be? These two teas taste and

look so different! And to make it more

complicated: white, oolong and pu’erh teas

come from this same plant and are even

more different in flavor.

These different types of tea are created by natural processes — encouraged and carefully controlled by the tea maker.

What keeps green tea green? And what makes black tea black? What about other teas? Let’s explore.

Tea! The World in Your Cup THE SCIENCE OF TEA

Experience Tea Studio

A Little Science in your Cup of Tea!

Camellia sinensis is a plant species that is

thousands of years old and is thought to first

grow in southern China. It is a bush (but

sometimes a tree) with green leaves and it is

the leaves that make our coveted drink: tea!

Some varieties of this plant even grow to be

tall trees! There are some very old tea trees

in southern China’s Yunnan Province.

All tea is produced from the same plant:

Camellia sinensis. The differences in

chemical composition, color, taste and

aroma are created by controlling the degree

of oxidation during processing. In particular

— the steps of oxidation, stopping the

oxidation, forming the tea, and drying it all

impact color, taste, and aroma.

Only the very youngest leaves are picked

(plucked) for tea. The processing of the

leaves must begin right after they are

plucked. There are a few different varieties

and many hundreds of hybrids or unique

types of tea plants. Tea makers choose

hybrids that grow well in their soil type and

weather.

Tea contains lots of different chemicals, but

the main ones associated with the taste,

aroma, and health effects of tea are

polyphenols – mainly flavonoids. The plant

produces these chemicals not for our benefit

but to help the plant fight against predators

and stress.

Polyphenols make up approximately 30% of

the dry weight of the leaves of the tea plant.

Other chemicals that contribute to the flavor

and effects of tea (but to a lesser degree)

include caffeine and amino acids, mainly

theanine.

Tea is one of the most popular beverages in

the world, having been consumed for

thousands of years.

Camellia Sinesis—One Plant, Many Teas 1

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When the green leaves are picked, they

start to degrade and will turn black within a

day or so. Leaves of the tea plant, like all

plants, are made up of many, many cells

that have certain compounds and enzymes

in them. Picking a leaf separates it from the

nutrition and support of the bush and the

leaf cells start to lose moisture and collapse.

Some compounds that naturally stay

separate begin to mix and make new

compounds—turning the leaves black. This

is called oxidation.

China discovered that heating the fresh

picked leaves would keep them green.

Heating deactivates the enzyme in the leaf

cell

that

causes blackening or oxidation. They also

discovered that rolling the leaves after

heating gave the tea more of a vegetal,

green taste—which is very characteristic of

green tea.

Black tea, on the other hand, are the leaves of this same plant. The difference is that the tea maker encourages the blackening of the leaves (oxidation) and does this through a complex process of withering (softening) and rolling. During this process, the leaves are laid out and allowed to turn black before the final step of heating.

Do a taste test of black and green tea.

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Tea! The World in Your Cup THE SCIENCE OF TEA

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Tea plants love sunlight and water—thriving

in a subtropical environment— and ideally

free of predator bugs. If any of these

conditions change adversely, the plant gets

stressed.

Stress is usually not a welcome feeling for

human beings, but with the tea plant stress

might translate into heightened and/or

unique flavor. When the tea plant is stressed

by lack of water or low sunlight, it creates

more of some protective compounds to

compensate and protect its survival. Some

of these additional compounds lend good

flavor to the tea.

Here is an example: there is a bug in Taiwan

called a jassid. For a certain type of tea, the

tea farmers hope the jassid makes an

appearance in the summer to nibble on

their tea plants. This is because as the

plant is stressed by the predator, it produces

compounds to ward off the bug and these

compounds create a wonderful honey-like

aroma and taste.

Have you heard of matcha tea? This is a

ground green tea popular in Japan and used

in the Japanese Tea Ceremony. The

Camellia sinensis tea plants for matcha are

shaded with black fabric during the growing

season in order stress the plants and

heighten certain flavor characteristics.

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Tea! The World in Your Cup THE SCIENCE OF TEA

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The science of enjoying a good cup of tea

doesn’t stop with growing and processing

the leaves: steeping or brewing the tea

correctly helps ensure that the finished tea

gives you wonderful flavor in your cup!

Basically, when you steep tea you are

coaxing the leaves to release their best taste

expression through temperature of the water

and the time the leaves sit in the water.

Since we have been talking mostly about

green teas and black teas, we’ll focus on the

steeping preparation of these two teas.

With green teas, a temperature that is quite

a bit cooler than boiling (175F) brings out

the best flavor. In addition, we want to limit

steeping time to 2 minutes for green tea.

Why is this? The finished green tea is

sensitive due to the heating and rolling

processes we talked about above. The

compounds within the leaf are released very

easily when in contact with hot water and

some of these compounds are bitter. By

using hot, not boiling water, and limiting the

steeping time, we “pace” the amount of bitter

compounds that are released into the cup.

Many people think they do not like green tea

because they find it bitter, but maybe it’s

because they steeped the tea too hot and

too long.

For black teas, we almost always want to

use boiling water (there are a few

exceptions) and steep the tea for four or five

minutes. The very hot boiling water brings all

the flavor compounds out of the leaf and this

is what gives us the wonderful complex taste

of good black tea.

Some tea experts determine the temperature of water this way:

• When you see fish eyes along the side of the kettle, the water is hot enough for white and green teas.

• When you see a string of pearls along the inside of the kettle, your water is hot enough for Oolong tea.

• When the water comes to a roiling boil, your water is ready for black teas.

How to brew tea is a matter of personal

choice – there is no one ‘right’ way.

However, there are many customs and

rituals associated with drinking tea that have

developed in different cultures around the

world, which we will discuss in a different

part of this patch series.

Watch this video from the BBC on the

science of tea and how Britons have

been making their tea all wrong.

It’s All About the Brew 4

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How to make the perfect cup of tea? Start with a great tea or tea blend. Your choice of tea will dictate the necessary water temperature and the time needed to steep.

Most Americans use commercial tea bags, but to truly enjoy a cup of tea, loose leaf might be a better choice. While teabags provide convenience, they are generally made from machine cut dry tea leaves and include tea dust. Loose leaf tea is generally larger tea leaves which maintain more oils.

Do a quick comparison. Cut open a teabag and pour the tea onto a small plate or bowl. Then scoop a teaspoon of loose leaf tea. What differences do you see?

Now for a taste test. Try making a cup of tea using a commercial tea bag and a second cup made from loose leaf tea.

1. Brew your tea bag as you would usually.

2. Follow the directions below to make a loose leaf tea.

• Pre-heat your tea pot with hot water and then pour it out. This is called tempering your pot.

• One teaspoon of loose tea per cup and one extra teaspoon for the pot.

• Boil the water to a roiling boil. Note: most modern electric water kettles over boil the water. White and green tea should have 180 degrees. Oolong should be 200 degrees. Black tea should have water at 210 degrees.

• Use filtered water, if possible.

• Steep for a minimum of 5 minutes. Some teas may take longer, like a Darjeeling.

• Stir the pot before pouring.

• Pour over a tea strainer into your cup.

• Add milk, cream or lemon (never both), and sweetener.

• Stir your cup in the gentle back and forth movement (between 6 and 12 o’clock).

Use your senses to review your teas. How do the two cups smell? Can you see any differences in color or texture? How do the teas taste?

Think back to how you made your tea using the tea bag. How long did you steep it? How does it compare to the process of brewing a loose leaf tea?

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Tea! The World in Your Cup THE SCIENCE OF TEA

Experience Tea Studio

Tea! The World in Your Cup THE SCIENCE OF TEA

Experience Tea Studio