If you are like me, a hot cup of tea can be just what the doctor (or therapist) ordered, but where do the leaves come from and how are they prepared? Are they fermented or oxidized, and what is the difference? Because the various methods of processing is what results in the type of resulting tea, I dug a little deeper to find out just how tea is made and why it matters.
Teas are oxidized for different amounts of time, and is a process that is often falsely called fermentation. White and green teas undergo minimal oxidation, while oolong teas are semi-oxidized and black teas are fully oxidized with some fermentation. Certain varieties like Pu’er and Kombucha extend the fermentation process for unique flavors and health benefits.
The oxidation process requires exposing tea leaves to air for a period of time to develop flavor while fermented tea leaves actually begin to break down from prolonged exposure.
The terms “oxidation” and “fermentation” are sometimes used interchangeably, but they refer to two different phases of the process.
Because the end results will create different types of teas, it’s worth knowing about the processes, the differences between the two, and the types of teas each process produces.
“Teas are oxidized for different amounts of time, and is a process that is often falsely called fermentation. White and green teas undergo minimal oxidation, while oolong teas are semi-oxidized and black teas are fully oxidized with some fermentation. Certain varieties like Pu’er and Kombucha extend the fermentation process for unique flavors and health benefits.”
TEA CROSSING
You may also want to read my article Is All Tea Really from the Same Tea Plant in China?
Let’s take a look.
Oxidation vs. Fermentation
All tea, whether green, black, oolong, or other, comes from the same tea plants, also known as Camellia sinensis.
Once these leaves are picked, they are dried and processed to enhance the natural flavor of the plant.
Depending on the desired result, tea leaves are dried and either oxidized or fermented, or sometimes both.
The oxidation process changes the color of tea leaves, turning the leaves from green to black. The process is stopped by cooking the leaves through slight exposure to heat. While there are several different methods that tea producers use, all teas are oxidized for different, specific periods of time.
Fermentation is defined as the extraction of energy from carbohydrates when oxygen is lacking. This means that it only occurs at the end of the oxidation process, so most teas are not fermented.
While white, green, and oolong teas oxidize as the leaves are dried, only those black teas that are exposed to prolonged oxidation naturally begin to ferment. The fermentation process has, however, also been intentionally implied to create other unique varieties.
Tea from Plant to Cup: The Process
Tea is traditionally made from the young shoots of the Camellia sinensis plant and can be dated back to China’s Shang dynasty of approximately 5,000 years ago, at which time it seems to have been used for medicinal purposes.
Today, tea has spread in popularity and is enjoyed for its many tastes and health benefits in many countries around the world.
Tea leaves immediately begin to wither upon being plucked, so the process requires much care and skill. From picking them at the right time to processing them in the correct manner, any small change can drastically alter the end result in terms of flavor, aroma, and nutritional values.
After the tea leaves are picked, they are set to wither a bit to soften before being rolled. In modern tea factories, the leaves are spread out on bamboo or stainless-steel troughs and the heat and humidity are strictly controlled.
Amino acids and simple sugars arise during the process, and the tea’s fragrant aroma comes forth as complex compounds break down. The whole process can take up to a day, depending on the conditions, and when the leaves are ready is determined by their feel and smell.
The premise of rolling the withered leaves is to break the cell wall, releasing the inner juices of the leaves and speeding up the oxidation process.
This process is done in one of two ways:
- Rolling the leaves
- Mechanically macerating the leaves
Rolling and maceration ruptures the cells of the withered leaves and exposes the cell sap, the molecules which contain the polyphenolic compounds that give tea its flavor and aroma. Once the cell sap is exposed to air, it begins to oxidize.
Teas are then laid out to dry and oxidize which develops the flavor of those polyphenolic compounds as oxygen is absorbed. Heat is introduced through different methods to stop the oxidation at a desired level.
This video by the Madar Tea Company does a great job of giving insight into the tea production process.
Types of Tea Focused Primarily on Oxidation
The different categories of teas are white, green, oolong, and black and each is determined by the level of oxidation and fermentation. White teas are very slightly oxidized and are generally made from younger and more tender shoots of the tea plant, while green teas are oxidized a bit longer, oolong teas are semi-oxidized and black teas are fully oxidized.
The section below compares the oxidation levels and flavor profiles of popular teas.
White Tea
White is made from young, tender shoots of the tea plant and undergo minimal processing to retain the naturally sweet and subtle flavors. White teas are low in caffeine, but some people claim that harvesting the young plant means that the tea retains higher levels of antioxidants.
Because white tea uses such young buds off the tea plant, it is the most sensitive variety. White teas are best brewed with lukewarm water so that the leaves aren’t scalded in the brewing process. Using near-boiling water to brew hot tea would burn the leaves and produce a bitter beverage.
Popular types of white tea include the following:
- Silver Needle or Baihao Yinzhen, the most famous type of white tea made from light silver buds.
- White Peony or Bai Mudan, a combination of buds and leaves that create a stronger flavor than that of silver needle tea.
- Long Life Eyebrow or Shou Mei, made from the left over leaves from silver needle and white peony teas.
Green Tea
Green tea is relatively new in the western world, really only gaining popularity through fitness crazes since the 1990’s. It has, however, grown rapidly in popularity, especially with the introduction of a variety of flavors to sweeten green tea’s naturally earthy flavor.
Green teas are made from the mature leaves of tea plants and undergo the shortest time spent withering. This means that the natural aromas do not have as much of an opportunity to come forth as in other teas, leaving green tea with a grassier scent. The shoots of the tea plant, however, undergo a slightly longer processing and oxidation than white teas.
Chinese green teas are generally considered lower grade than Japanese green teas due to the way they are processed. The oxidation process of Chinese green tea is halted by frying the leaves in a pan, which results in a slightly toasted flavor and aroma and a darker, brownish/yellow color.
Chinese green teas include the following:
- Dragonwell
- Fur
- Peak
- Gunpowder
- Green Snail Spring
- Hyson Lucky Dragon
For Japanese green tea, on the other hand, the oxidation process is stopped with steam. This retains a vibrant green color and a fresh, grassy flavor.
Japanese green teas include the following:
- Bancha
- Ganmaicha
- Gyokuro
- Matcha
- Sencha
Like with white teas, green teas should be brewed with warm, not boiling, water so that the resulting beverage isn’t bitter.
Matcha and Sencha Tea
Matcha and sencha teas are powders that are made from dried green tea leaves that can be brewed into a traditional, ceremonial beverage. Matcha is a high-grade, ceremonial quality tea while sencha is the name given to lower-quality instant green tea powders.
Oolong Tea
Oolong teas are semi-oxidized, meaning that they make up the range between green teas and black teas. Anything that is between 5% and 85% oxidized is considered to be an oolong, so this category is broad and inclusive of a great variety of variation in the boldness of the flavors and aromas as well as the types tastes and scents that can be drawn out of the leaves.
Oolong is easily recognizable because it has much longer leaves than are found in green on black tea that are found scrunched up into balls that unfurl as they steep. Many oolong teas are made with the highest quality plants and deliver both the subtle, earthy flavors of green tea and the richness of black tea. Oolong teas are picked and oxidized to their desired extent, then heated to halt the oxidation process and preserve the desired state.
Skilled oolong tea makers will also consider factors such as ensuring that the leaves are tossed and bruised in a way that correctly releases the liquids or allowing the leaves to rest long enough to achieve different desired flavors.
The roasting time of oolong can also greatly affect the flavor. While light or “jade” varieties of oolong can be green enough to be mistaken for green tea, though the higher oxidation levels along it being more roasted brings out more complex floral and buttery flavors than are found in plain green teas. The more the tea is oxidized, the deeper and warmer the flavors become as the spices and flavors come out, with heavily oxidized oolong being reminiscent of coffee in its boldness.
Although there are many different varieties of oolong, some of the most favorite choices include the following:
- Chinese Phoenix oolong, made from a plant who’s leaves are tall enough to require ladders and that produces a uniquely woody flavor.
- Taiwanese Dong Ding oolong, which has a sweet and smooth flavor at a 30% oxidation level.
- Taiwanese Jin Xuan, also known as milk oolong, is sweet and smooth enough to feel creamy.
- Taiwanese Oriental Beauty or Dongfang Meiren oolong has a 70% oxidation level and is sometimes considered to be the traditional form of Taiwanese tea.
- Darjeeling oolong, which is an Indian tea variety grown in Chinese fashion.
- Assam oolong, which is a tea that is smoked to bring out its flavors.
This article by teaallure.com is a great comprehensive guide to the many types of oolong tea and even features some great visuals to clarify the production process.
Oolong is best brewed with close to boiling water and for a short amount of time.
Black Tea
In the modern world, black tea is statistically the most consumed type of tea throughout the world, making up approximately 80% of all tea sales.
Black tea today was traditionally Chinese red tea, although it wasn’t even consumed in China until the mid 17th century.
Most black tea comes from India and is made from the Camellia assamica species which has a high yield, high caffeine levels, and bold flavor.
They are exposed to air for long periods of time to allow the green leaves of the tea plant to oxidize into a darker color and are sometimes allowed to ferment. Fermentation is a natural, exothermic reaction involving enzymatic oxygen and the polyphenolic compounds in the cell sap.
Black teas, when brewed, have a deep red color, hence the original Chinese name, as well as a rich deep, flavor. Black tea is also often mixed with spices, fruit peel, and other flavors. Black teas have less caffeine than green teas but carry more antioxidants.
Many black teas are exposed to prolonged oxidation and begin to ferment. Some teas, like Pu-erh teas, are exposed to prolonged fermentation as they are aged for months, or years in some cases, to develop deeper, richer flavors.
Chinese black teas include the following:
- Keemunqi
- Lapsang
- Yunnan
Indian black teas include the following:
- Assam
- Darjeeling
- Nilgiri
Sri Lankan black teas include the following:
- Ceylon
“Making tea is a science that has been developed, refined, and expanded upon in different regions of the world for centuries.”
TEA CROSSING
Types of Fermented Teas
While the process of producing tea generally revolves around the oxidation process, there are certain types of teas outside of certain black tea varieties where the focus is instead on fermentation, creating a whole new variety of flavors, mouth feels, and health benefits.
Pu’er Tea
Pu’er, or pu-her tea, is relatively new to the western world and is considered in a similar category as fine wine. It can come raw (partially fermented) or ripe (fully fermented), the tea becoming less acidic the more it is fermented. Raw pu’er has a long history of trade, while ripe pu’er has become the popular choice internationally.
Pu’er comes in both green and black varieties but is unique in that it is sun dried to promote fermentation, a process that gives it a unique flavor. Ripening this tea happens in a process that is similar to composting, and the flavors of the tea only increase the longer it is properly stored.
Kombucha Tea
Kombucha tea is fermented after it is brewed using yeast, sugar, and bacteria, similar to the process of making yogurt or vinegar. Kombucha teas are traditionally made from brewed black or green tea but can be made using herbal teas as well.
Kombucha is made using a scoby or “symbiotic culture of bacteria and yeast” which eats the sugars that are added to brewed, acidic tea. The scoby ferments the tea over 7 to 10 days and turns it into kombucha, a slightly sour drink rich in probiotics.
Other Blends Commonly Known as “Tea”
Although there are many blends that are referred to as tea, a blend is technically only tea if it actually contains tea leaves. If not, the blend is referred to as tisane, the Greek word meaning “non-tea”. Below are some popular varieties of tisanes.
Rooibos
Rooibos, or red tea, technically isn’t tea at all. It is harvested from a red bush called Aspalathus linearis that is native to South Africa. The leaves and shoots of the bush are dried and brewed into a beverage that has naturally sweet, vanilla flavor notes. Rooibos is dried and is neither fermented nor oxidized.
Rooibos is naturally caffeine free, making it a great choice for anyone who is caffeine sensitive. It is also low in tannins that can reduce the absorption rate of iron, but rich in free-radical fighting antioxidants.
If you have little ones to care for, you may want to read my article 17 Reasons Rooibos Tea is Good for Babies and Toddlers.
Other believed benefits of rooibos tea include the following:
- Allergies
- Colic
- Digestive problems
- Insomnia
- Mental health issues
- Poor appetite
This article by Medical News Today goes into more depth about the benefits of rooibos tea.
Hibiscus, Chamomile, and Other Floral and Herbal Teas
Herbal teas and teas that are flavored with fruit contain the dried buds of flowers, dried fruit peels, and other dried parts of plants. While some mixes that are falsely called teas are actually just blends of different dried botanicals, others are blended with actual tea leaves.
Hibiscus teas, for example, are simply made from the dried leaves of hibiscus flowers, and the same is true for chamomile, rose, and other popular floral varieties. These teas are also often brewed with dried fruit peels for added flavor, and they can sometimes be found blended with different types of tea as a way of adding flavor and caffeine to the blend.
Chai
The word chai means “tea” in Hindi and stems from the Chinese word cha which also carries the same meaning. Although chai does often include black tea, it is heavy in a variety of spices including the following:
- Ginger
- Cinnamon
- Black pepper
- Cardamom
- Cloves
Chai is often sweetened and mixed with milk, but can vary greatly depending on the regions it stems from and is consumed in.
Yerba Mate
Although yerba mate is similar to tea, it stems from a different plant, the holly plant called Ilex Paraguariensis that is found native to south America. It has grown in popularity due to its natural caffeine content and has been commonly found sold in stores as an alternative to coffee or energy drinks.
Making tea is a science that has been developed, refined, and expanded upon in different regions of the world for centuries.
Although the oxidation levels of tea leaves are one of the main focuses in the process of creating excellent tea, many other factors play into the process to create each unique blend.
When the process is carried out long enough for it to go into fermentation, a whole other world of possibilities opens, and when other spices and botanicals are brought into the equation, there is enough variety for there to be a type of tea that is sure to please any palate, even your doctor’s or therapsist’s.