Let`s talk about how oolong tea is made.

Oolong tea is a common tea-making method. It involves many steps, and when you want to understand it deeply, you often encounter the fact that each tea master has their own unique techniques. Listening to their explanations is like doing tai chi in the clouds and mist. It seems understood, but in reality, it`s still unclear. The process of making oolong tea is like a fermentation journey. The starting point of the journey is called green tea, the endpoint is called black tea, and the journey itself is called oolong tea. To see which scenery you want to see during the journey, it relies on your own experience and imagination. Making oolong tea can also be likened to hydraulic engineering. If the water in the tea leaves can be drained smoothly, the oolong tea will taste good.

Why is it compared to hydraulic engineering? When the leaves are picked from the tea tree, they contain about 80% moisture. By the time the processing is complete, the moisture content is reduced to 5%. This means that at least 75% of the moisture is removed during the tea-making process. As a result, various chemical substances that were originally present in the tea leaves undergo a series of complex chemical reactions due to the reduction in moisture.

Before we delve into the tea-making process, let`s imagine ourselves in a kitchen enclosed in a large water bubble, with many water pipes connected to its surface. Inside, there are many chefs and a large refrigerator filled with ingredients. Normally, these chefs don`t cook much, and the refrigerator isn`t frequently opened. Suddenly, one day, the water pipes outside the water bubble start draining water, and for some reason, the refrigerator door can`t be closed properly. As the space diminishes due to the disappearing water, the refrigerator gets closer and closer. It`s time to start cooking. This is the biochemical process of tea making.

In the tea-making process, we all know that the first step is to pick the tea leaves from the tree, known as plucking. So, what is the standard method of plucking? It`s called “bud and two leaves plucking.” How do you do it? First, open your hand and let the tea buds rest in the space between your thumb and index finger. Then, use your index finger to feel for the stem of the tea leaf. You`ll notice that the segment of the tea leaf from your index finger to your thumb is about one bud and two leaves to one bud and three leaves. Next, use your thumbnail to press against the stem of the tea leaf at the second joint of your index finger, then press it between your thumb and index finger. Repeat this motion continuously. You`ll find that all the tea leaves are about the same length and consist of one bud and two leaves to one bud and three leaves. However, it takes a lot of practice to do this.

So, what is the incorrect method of plucking? It`s called “cutting vegetables” or “slowly picking vegetables” in Taiwanese. It`s like harvesting vegetables, where the tea leaves are picked one by one regardless of their length. What`s even more unusual is that I`ve seen tea leaves being harvested with small sickles before.

How to determine when the tea leaves in the tea garden are ready for harvest? Simply by observing the growth of the top tea buds. If the top buds have just emerged, it means they are too young. If the top buds have grown but have just opened, it`s called “opening.” If all the tea buds have opened fully, or even formed small white buds resembling rice grains, it means they are too old. These rice grain-like small white buds are called “bud dormancy” or “dormant buds.” The best time to harvest is when the top buds have just opened. If the tea garden is too large, harvesting should be done a bit earlier to prevent the last harvest of tea leaves from becoming too mature. After harvesting the tea leaves, pruning is necessary to trim the tea bushes so that they grow at the same rate for the next harvest. Then, you only need to wait for about 50 days before the next harvest. The length of the waiting period depends on the duration of sunlight and temperature. If the tea bushes are left to grow without pruning, they will grow randomly, and I have seen people using ladders to harvest tea leaves in Lishan. Additionally, tea harvesting is done according to the solar terms. For example, spring tea is harvested around the Grain Rain period, and the well-known “pre-Ming” tea refers to tea harvested before the Qingming Festival, which is about 14 days before Grain Rain. Tea leaves harvested at this time are very tender and suitable for making green tea. By the way, the regions where tea leaves are harvested according to solar terms are usually at altitudes below approximately 1500 meters. If the altitude exceeds this height, the harvest time will be delayed because there is less sunlight and it is colder, resulting in slower tea leaf growth. For example, in Lishan, spring tea harvesting usually begins at the end of May or early June, while in the plains, summer has already begun.

Apart from hand-picking, machine harvesting is also common, commonly known as mechanical harvesting. As the name suggests, machines are used for harvesting. Common tools for machine harvesting include single-person clippers, two-person checkers, and ride-on tea harvesters. Machine harvesting of tea leaves requires skill, especially in controlling the depth of the machine`s operation. If the machine is not handled properly, it`s easy to cut leaves that are too long or cause leaf breakage. Many people say that machine-harvested tea leaves are not good, and I think this issue needs to be explored further. The term “not good” here refers to the fact that machine harvesting can cause leaf breakage, resulting in poor tea flavor and an impure taste when brewed. From a tea garden management perspective, machine harvesting can injure the tea bushes, and if done too frequently, it can shorten the lifespan of the tea bushes. Overall, if the frequency of harvesting is reasonable and broken leaves are removed after processing, I believe the tea brewed from such leaves will be delicious.

Can high-mountain tea be machine-harvested? In theory, yes, but there are natural limitations, namely the terrain. Because tea harvesting machines are usually heavy, even harvesting tea leaves on flat ground is quite labor-intensive. Operating these machines on steep slopes in high mountains would be quite challenging. Not to mention using ride-on tea harvesters.

So, why pick one bud and two leaves? Wouldn`t picking just the bud be better? In fact, picking one bud and two leaves aims to balance the flavor. The tea bud, when brewed, has sweetness but can also be bitter and astringent without much aroma. The leaves, on the other hand, are sweet and aromatic but lack sweetness. So, by picking one bud and two leaves, the resulting tea is both aromatic and sweet with a lingering aftertaste, and it can withstand brewing with boiling water.

In addition, many people think that farmers should work at sunrise, but tea picking cannot be done then. It`s necessary to let the morning sunlight shine on the tea leaves for a while, allowing the dew on the surface to evaporate before picking. If the tea leaves are covered in dew or it`s raining, it will make the subsequent tea-making process quite challenging, and it`s not easy to produce good tea. Currently, there are very few young people in Taiwan who pick tea in the mountains. Instead, there are “thousand-year-old” teams and international teams, often consisting of people from other countries like Vietnam and Thailand.

Tea picking wages are quite attractive because they are paid based on weight. As long as the tea picking speed is fast enough, workers can usually earn a handsome wage. However, there is a fatal flaw: if the picking speed is not fast enough but workers still want to earn more money, what should they do? They pick longer leaves. We often hear that tea leaves should be picked one bud and two leaves or one bud and three leaves. Picking longer leaves means picking more leaves. Some people jokingly say that nowadays, tea picking in the mountains is not about picking one bud and two leaves anymore; it should be called “five-leaf pine,” “seven-leaf gall,” or “nine-layer basil,” referring to picking multiple leaves. Picking too many leaves will make the subsequent tea-making process quite troublesome.

Another method to earn a bit more from tea picking is to start picking earlier. Some tea pickers sneak into the tea garden with their baskets before the sun rises and start picking tea leaves. After picking a large amount, they forcefully stuff them into the basket and wait to take them out officially when work begins. This method is both amusing and frustrating because the tea leaves are soaked with dew and sticky, and many of them are damaged due to excessive pressure.

After tea picking, the next step is sun-drying, which allows the fermentation of the tea leaves to proceed smoothly under the sunlight. I believe that the taste of oolong tea is the taste of the sun. It`s like drying clothes: clothes dried in the sun have a different smell and comfort level compared to those dried in a dryer. During the tea picking season, you can see trucks rushing on the roads, carrying baskets the size of oil barrels filled with freshly picked tea leaves. They drive so fast because they are afraid that the tea leaves will be compressed for too long, causing heat to be trapped and damaging the leaves. As soon as the tea baskets are taken off the truck, the first thing to do is to spread out the tea leaves and expose them to the sunlight. This step is called outdoor withering. If the sunlight is too strong, black nets can be used to reduce its intensity. The ideal sunlight intensity for outdoor withering is the level that feels comfortable to people.

Some may ask, how long should the tea be sun-dried? This question is very difficult to answer because it depends on the weather, including temperature, wind direction, humidity, and the total amount of tea leaves to be harvested today. Here, “tea leaves” refer to the leaves picked from the tea trees. In practice, the duration can vary from no sun-drying to sun-drying for two to three hours. When is no sun-drying needed? During midday, because the tea leaves have already been exposed to the sun on the trees.

How do we determine if the tea leaves have been sun-dried properly? Many people say that the tea leaves should have a misty appearance on the surface. Here, “tea leaves” refer to the majority of the leaves, not every single leaf. If every leaf becomes misty, then it`s overdone, indicating that the tea leaves have been sun-dried excessively. Tea production emphasizes stable averages. In other words, if 80% of the leaves meet the requirements, it`s considered acceptable. If 100% meet the requirements, it means that some leaves have exceeded the requirements, which can lead to a loss of control over the quality of the tea. Additionally, besides observing the misty appearance, you can also smell the aroma. If the grassy aroma is not too strong, it indicates that the leaves have been properly sun-dried. This grassy aroma is also referred to as “Jingwei” aroma.

Why is it said that the tea leaves should appear misty after sun-drying? We can discuss this from the chemical and physiological aspects of the leaves. Let`s go back to the analogy of the water balloon kitchen. When the water balloon kitchen is still connected to the tea tree, nothing happens. But when the water balloon kitchen is detached from the tree, the water pipes on its surface start draining, causing the room to shrink. From the outside, it looks like a waterless water balloon, so the tea leaves appear misty. Sun-drying not only accelerates moisture removal but also loosens the lock on the refrigerator door, causing the ingredients inside to start falling out. During the sun-drying process, gentle handling is required; you shouldn`t sprinkle the tea leaves too forcefully or grip them too tightly. This can cause the water pipes to malfunction, leading to poor drainage. Once drainage is obstructed, water will accumulate in the tea leaves, a condition referred to professionally as “water accumulation.”

We all know that Taiwan often experiences rainy weather. If, unfortunately, it rains continuously during tea processing, what should we do? The common method is to use hot air withering. This process takes place indoors, where the tea leaves are spread out and exposed. Dehumidifiers and electric fans are used to assist in draining excess moisture from the tea leaves. During outdoor withering, if the tea leaves are not spread out evenly and appear clumped together, resembling chicken scratches, it`s referred to as “chicken foot marks.”

After the tea leaves are sun-dried, they are moved indoors for stirring and resting. This process is called indoor withering. During this process, the tea leaves are flipped over, left for a while until they become soft, flipped again until they become straight and rigid, resembling they`ve come back to life. Afterward, they are left for some time before evenly processing them in a rolling machine. When the tea leaves smell sweet and the grassy aroma is not too strong, it indicates that fermentation is complete. This process takes about eight hours.

Besides relying on the aroma to determine if fermentation is complete, visual cues can also be helpful. At this stage, the tea leaves still maintain their green color but appear slightly darker. However, solely relying on color may not reveal much change. Instead, you can observe the tea stems. Due to moisture removal, the stems develop wrinkles. The edges of the tea buds may have a very subtle red border, and the first leaf below the tea bud may have red dots along its serrated edge. The third and fourth leaves may not show much change, making the entire tea leaf appear deflated like a deflated balloon. If most of the tea leaves exhibit these characteristics, it indicates that fermentation is complete. If the tea buds turn red, it means fermentation has gone too far, also known as “dead leaves.”

What is “green leaves with red edges”? Those who frequently drink tea may hear about traditional Dong Ding Oolong tea emphasizing green leaves with red edges. This refers to the first leaf of the tea leaf having a red border around its edge. This phenomenon occurs because the edge cells of the leaf are more prone to damage during agitation, coupled with being thinner than the middle of the leaf, resulting in rapid oxidation. This phenomenon was more common in the past when there was no air conditioning to control the fermentation speed. Nowadays, with the assistance of air conditioning equipment, it is easier to control the fermentation speed.

Now someone must ask why tea is no longer made with green leaves and red edges. This is because tea with green leaves and red edges tends to have a stronger flavor and less aroma. By reducing this phenomenon, the taste of the tea becomes lighter, and the aroma richer. This taste is more suitable for most consumers.

Let`s delve deeper into what happens during the fermentation of tea leaves. Before discussing fermentation, let`s first understand the definition of fermentation. Fermentation refers to the process by which organisms convert organic substances into energy, as seen in the production of beer and bread. However, there are no organisms involved in the fermentation process of tea leaves, such as yeast. Instead, the fermentation process of tea leaves is mediated by enzymes. Therefore, it would be more accurate to describe the fermentation of tea leaves as oxidation.

Why do people refer to the oxidation process of tea leaves as fermentation? It`s because in the early days, people didn`t have a deep understanding of biochemistry. During the tea-making process, heat and aroma are produced, similar to the fermentation process of bread. Therefore, it was called tea fermentation. Especially when introducing tea fermentation in English, using “oxidation” is more appropriate than “fermentation”. Now that we`ve clarified the difference between fermentation and oxidation, let`s discuss what actually happens during oxidation in tea leaf cells.

Oxidation is like rust forming on an iron nail, and the change in color of tea infusion is very similar. Let`s go back to the kitchen with the shrinking space: as the chef begins to cook the food that fell out of the refrigerator, in reality, it`s like stirring the tea leaves, and they start to smell fragrant. Once the chef finishes cooking the fallen food, they take a break, which in reality is allowing the tea leaves to undergo static fermentation, and eventually, the tea leaves lose their fragrance. Then, the chef must shake out the food from the refrigerator again and continue cooking, which is stirring the tea leaves again. This process repeats several times until the chef has cooked enough food, which in tea terms means the tea starts to smell fragrant, indicating that the fermentation of the tea leaves is complete.

By the way, why do the tea leaves “come back to life” after stirring? This is because the water in the tea stems redistributes to the leaves. It`s like the water pipes in the kitchen bring some water back from the tea stems, so the leaves appear to “come back to life”. The endpoints of these water pipes are the edges of the tea leaves and the bottom of the leaves, both of which have openings to release water into the air.

Why do tea leaves darken during the manufacturing process? In addition to water drainage, we also notice that the color of tea leaves gradually darkens. This is because the chlorophyll in the tea leaves begins to change, undergoing a process called “de-magnesiation”. After de-magnesiation, the chlorophyll appears darker. When we unfold the structure of chlorophyll, we can see it resembles a spider web, with the central “spider” being the chemical element “magnesium”. Chlorophyll is very sensitive to light and heat and undergoes qualitative changes. If we replace “magnesium” with “copper”, we get the famous synthetic pigment, copper chlorophyll. It is less susceptible to the effects of light and heat. There`s something in our bodies that looks very similar to chlorophyll, and that`s hemoglobin, except the chemical element in the middle of hemoglobin is not “magnesium”, but “iron”.

Why can`t large-leaf tea plants be used to make oolong tea? We often find that it`s usually the small-leaf tea plants that are used as raw materials for oolong tea, while large-leaf varieties are less common. Apart from the fact that small-leaf tea plants naturally contain fewer bitter substances such as catechins or caffeine, their leaf structure, including the cuticle layer and the lattice structure, is thicker compared to that of large-leaf varieties. This allows them to withstand the mechanical pressure caused by rolling and oxidation better, and also slows down the loss of moisture.

The frying process: Once oxidation of the tea leaves is completed, the next step is to halt the oxidation process, which is achieved through frying, also known as “fixing”. This step uses high temperature to deactivate the oxidative enzymes, thus stopping the oxidation process. How do we determine if the frying process is complete? How long should the tea leaves be fried for? Typically, it`s about 8 to 9 minutes at temperatures ranging from 270 to 300 degrees Celsius. When it`s done, the tea leaves should feel soft to the touch with a slight prickly sensation, which is caused by the dryness of the leaf edges. Additionally, there should be no grassy smell, indicating that the tea leaves have been properly fried.

The biochemical process of frying: Some say frying kills the enzymes, but in cellular terms, it`s more accurate to say that they lose their activity. What are enzymes? Enzymes are proteins that accelerate chemical reactions but are not consumed in the process. An example is hydrogen peroxide disinfection: when dropped on a table, it slowly releases oxygen and turns into water. However, when applied to a wound, it vigorously bubbles, indicating the presence of enzymes in our bodies that accelerate the breakdown of hydrogen peroxide into oxygen and water. So, what does it mean when enzymes lose their activity? It means that their shape changes or they break down, rendering them non-functional. Enzymes are like a special-shaped screwdriver; when their shape changes, they can`t perform their intended function. Heat is a good way to alter the shape of enzymes, and this reaction is irreversible.

After the tea leaves are fried, about 80% of the oolong tea-making journey is complete. The next step is rolling, which breaks down the structure of the tea leaves, making it easier for the tea`s flavor to dissolve in water. It`s like breaking down the walls of the kitchen in our analogy, allowing us to better taste the ingredients inside. If the tea leaves are dried at this point, it`s the production method for Wen Shan Bao Zhong tea. Many people think that the tea becomes granular after rolling, but in fact, the tea leaves take on a strip-like appearance.

How do we determine if rolling is complete? Tea leaves that have been properly rolled should feel slightly sticky when touched by hand, but this stickiness should disappear after a few seconds. If there is a lot of tea dust after rolling, it indicates that the tea leaves have been fried too dry. If the tea leaves stick together excessively after rolling, it means that the tea leaves haven`t been fried enough, or there was an issue during the withering process.

Round rolling process: Why retain the shaping process? This is because tea leaves shaped in this way tend to have a stronger flavor, which is quite different from Wen Shan Bao Zhong tea. The shaping step is also known as round rolling. How is this process carried out? First, the tea leaves are heated to make them soft and elastic again. Then, a large piece of cloth is prepared to wrap the tea leaves. Grasping one corner of the cloth, it is vigorously rotated to compress the tea leaves inside, forming a large tea ball. Next, whether by hand, foot, or machine, the tea ball is kneaded until it becomes soft, similar to rolling dumplings. When the originally tense cloth becomes loose, indicating that the tea ball has shrunk in volume, the cloth is opened, and the tightly compressed large tea ball is loosened before being wrapped back in the cloth for further compression and kneading. This process is repeated dozens of times until the tea leaves gradually curl into individual shapes. Typically, a large tea ball weighs about 18 kilograms. If you have the chance to handle it, its hardness is comparable to a bowling ball and quite heavy. Once the tea leaves have been curled into semi-spherical shapes, they are dried until their moisture content is below five percent, at which point the tea leaves are considered finished and are referred to as “maocha.”

The content shared today focuses on providing a simple explanation of the principles and operational processes involved in producing oolong tea. When actually making tea leaves, one would find the process quite challenging, as the signals indicating the completion of each step are often subtle.

To summarize today`s content, the production of oolong tea can be likened to a hydraulic project and is akin to the oxidation process of iron rusting. Throughout the process, catechins and other chemical substances in the tea leaves undergo continuous oxidation, producing aroma. When the tea leaves are perceived to be full of aroma, the frying process is carried out to halt the oxidation process. Rolling makes the contents of the tea leaves more soluble in water, while round rolling enhances the flavor of the tea leaves. If the moisture in the tea leaves can gradually be expelled during the production process, good-quality tea leaves can be produced.

Tea manufacturing chemistry: This is a more challenging aspect. Let me explain the original name of the “water ball kitchen” analogy. The water ball kitchen represents plant cells, the refrigerator represents the vacuole, and the ingredients mainly consist of polyphenols such as catechins. The chef represents polyphenol oxidase (PPO), the water pipes outside the water ball kitchen represent the protoplasmic strands, which connect to the veins, and the drainage holes at the leaf margin cells and leaf bottom cells are referred to as the defense cells. Now, let`s talk about the chef cooking, which is the oxidation of catechins by polyphenol oxidase. Catechins, also known as tea tannins, personally, I don`t agree with the term “tannin” because tannin is a natural chemical used by plants for self-defense and is commonly used in industries to produce leather by removing proteins. However, the tannin in tea leaves doesn`t have such strong functions. Catechins in tea leaves play a role similar to sunscreen. The stronger the sun, the more sunscreen is produced, which is why tea leaves grown at lower altitudes tend to be more bitter. When catechins oxidize, they turn into theaflavins, then into thearubigins, and finally into theabrownins. As they progress, their molecular weight increases, meaning their overall structure becomes larger. So, what compound is most abundant in oolong tea? It`s not theaflavins; theaflavins are used to judge the quality of black tea. Research has found that it`s oolongin, but because it`s not easy to study, there is very little related information available.

Finally, let`s talk about this chef, polyphenol oxidase (PPO). When the water ball kitchen is full of water, he doesn`t want to work much. But if the ingredients in the refrigerator come out, he will still cook them slightly. Only when the water in the water ball kitchen gradually dissipates and the overall environment changes from neutral to acidic, does this chef wake up and start working properly. However, there`s a limit to how fast he can work. If too many ingredients are given to him at once, he might cook up something unexpected. In practical operation, this could mean exerting too much force during tea leaf rolling or doing it for too long, resulting in off-flavors or even water retention.

That concludes today`s sharing. The content was quite extensive, aiming to provide a systematic understanding of tea leaf production. Hopefully, when you have the opportunity to delve deeper into tea leaves in the future, you`ll have a direction to follow.