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All About Tea

Tea has been harvested and brewed for over 3,000 years. As one of the oldest and most consumed beverages in the world, tea is a celebration of human history and our relationship with nature. It is enjoyed in cultures and traditions around the world, and Open Heart Tea Company aims to raise awareness and appreciation of it here in North America.

Tea Processing

All tea leaves come from the same plant, Camellia sinensis, and are classified into different categories based on how the leaves are processed--namely, the amount that a tea leaf is exposed to air; or oxidized.  Within each category there is variation in tea appearance, flavor, caffeine content, and aromas. There is an enzyme in tea which, when exposed to moisture and oxygen, causes the leaf to darken. How and at what stage this enzyme is deactivated defines the kind of tea produced. The following are the major processes used in tea production, and their purposes in classifying the major types of tea.

Pan Firing
Pan-firing involves the use of high temperatures to deactivate the enzymes and halt the fermentation of the leaves. It makes the tea limp by evaporating some of the water content in the leaves.
Withering helps evaporate extra moisture, activate enzymes that stimulate various chemical reactions inside the leaves, and make the leaves soft.
Rolling ruptures leaf cells to make tea juices rise to the surface of leaves and activate oxidation of enzymes. This further enhances the aroma and unique characteristics of the leaves.
Roasting halts the fermentation process and completely dries out the leaves, retaining their quality.
Fermentation occurs when microbial activity breaks down compounds in the leaf as a result of enzymatic oxidation. Non- or lightly-fermented teas retain their original green, fresh flavor, and fully-fermented teas are dark red, often with malty flavors. Post-fermented teas are allowed to ferment a second time and aged, often for many years. These Pu'erh teas have rich, complex, and earthy flavors and may go through heaping, a process of stacking up the leaves inside a humid, warm environment that stimulates chemical changes inside the leaves.

Black ("red") tea is fully fermented and high in caffeine, with a bright reddish infusion and rich aromatic flavor. During oxidation, the tea leaves turn dark red, brown, or black and add malty, fruity, or smoky aromas to the tea.

Principle methods for processing black tea: Plucking -> Withering -> Rolling -> Long fermenting -> Roasting

Oolong tea is partially fermented and relatively high in caffeine. It typically has bright, yellowish infusions with fresh, rich flavors and long-lasting, aromatic aftertastes. Oolong teas offer the widest character range among teas, from light and floral to dark and intense. To allow for partial oxidation, leaves are twisted and bruised and then heated. Some oolong leaves are rolled, which allows for complex flavor development as the leaves unfurl with each steeping.

Principle methods for processing oolong tea: Plucking -> Withering -> Light fermentation -> Pan-firing -> Rolling -> Roasting.


Green tea is not oxidized and therefore the leaves remain green. They are quickly steamed or roasted to prevent oxidation, and then dried. The infusions are generally yellowish green with a fresh, aromatic taste. In Japan, green tea leaves are typically steamed rather than roasted.

Principle methods for processing green tea: Plucking -> Pan-firing -> Rolling -> Roasting / Steaming


White tea is the least-processed style of tea. Traditionally plucked by hand to avoid damaging the leaves and exposing them to oxygen, white tea is made from the newest buds and leaves of the plant, which have soft, downy, white hairs. Once plucked, the leaves are laid out in the sun to wither, which stops the oxidation process. White tea has the least amount of caffeine and contains high amounts of antioxidant polyphenols and L-theanine amino acids.

Principle methods for processing white tea: Plucking -> Withering -> Roasting


Pu'erh tea is the post-fermentation aging of leaves that are processed as green, oolong, or black tea. The infusion is brownish red with a rich, mellow, earthy flavor. Black pu'erh may be referred to as "cooked," the transformation it undergoes due to natural fermentation rather than oxidation.

Principle methods for processing pu'erh tea: Plucking -> Pan-firing -> Rolling -> Heaping Fermentation -> Roasting

Herbal teas ("tinsanes") are not technically tea because they are made from herbs, flowers, and spices rather than from the Camellia sinensis plant. Cultures around the world have gathered and blended native plants to make various herbals teas, often for healing purposes.

Brewing Tea

Start with whole leaves, either loose tea or in tea bags that maintain the integrity of the leaves. The flavor of these teas evolve with each steeping rather than mass-produced tea bags that are usually made from chopped leaves, fannings, or tea dust. The strength of brewed tea depends on the ratio of leaves to water. Since each tea varies in weight, we recommend that you weigh leaves rather than measure them when brewing.

Use filtered water that is neither too hard nor soft, and pay close attention to temperature. Highly oxidized teas (oolong and black) need hot water to "wake up" the leaves (about 200°F), while green and white teas should have water that isn't as hot (about 175°F) to avoid activating bitter tannins or other cooked flavors.

Adjust your brewing time based on the size of your vessel and amount of leaves used. Generally, when using hotter water, steep the leaves for less time.  You may want to steep green and white teas for longer in lower temperature water. The complexity and quality of whole-leaf teas allow for multiple steepings.

The type of vessel you use can be based on the type of tea you like to drink, or what is available. Glass and ceramic teaware is good for a variety of teas, while a clay pot is recommended if you drink one tea most often. Keep in mind that the size of your pot will determine the water to leaf ratio and steeping time.

Tea Compounds

The chemistry of tea is complex. Some of the primary compounds may impact people differently, depending on each individual's system and sensitivity to stimulants and enzymes.

Caffeine is a stimulant found in coffee, tea, chocolate, and other products. Tea generally contains less caffeine than coffee (20-90mg in a cup of tea vs. 100-200mg in a cup of coffee). The amount of caffeine in tea is based on a number of variables including the plant varietal (more durable leaves tend to have more caffeine); the age of the source plant (older plants have more caffeine); the harvest season (later flushes generally have more caffeine); amount of sunlight (sunlight encourages caffeine production); age of the leaves (leaves picked later have more caffeine); and the brewing method/temperature of the water used to infuse tea (hotter water increases the caffeine level). The general amount of caffeine in a cup of each type of tea is as follows:

Black tea      60-90mg
Oolong tea   50-75mg 
Pu'erh tea    40-70mg   
Green tea     35-70mg
White tea     30-55mg 

Polyphenols are a compound of antioxidants that include flavonoids (tannins) that contribute to the bitter flavor of tea, and anthocyanin. These compounds - like wine - determine the tea's infusion, aroma, complexity, mouthfeel, and flavor.

L-Theanine is a rare amino acid that increases the production of alpha waves in the brain. L-theanine, in combination with caffeine, may improve brain function and contributes to the more mellow, relaxing effect produced by drinking tea versus coffee. These amino acids give tea its umami flavor, and tea is one of only three natural sources of theanine.

Enzymes, in particular polyphenol oxidase and peroxidase, contribute to the browning of the leaves when exposed to oxygen. The deactivation of these enzymes using heat is a key process in tea production. 

Tea leaves also contain chlorophyll, aroma compounds, and several minerals including fluorine and potassium. Additionally, herbal teas may contain spices, flowers, and herbs that have a variety of properties.