Green tea, white tea, yellow tea, black tea, oolong tea, dark tea... Can't tell the difference? Learn more in this article →

The application for "Chinese traditional tea-making techniques and related customs" has been successfully included in the UNESCO Representative List of the Intangible Cultural Heritage of Humanity. Today, let's talk about the science, history and secrets of Chinese tea.

From chewing fresh leaves, cooking raw tea, drying and storing, steaming green tea into cakes, frying green tea in loose form, to developing white tea, yellow tea, dark tea, oolong tea, black tea and other tea types, the Chinese have developed a unique tea culture. According to current customary classification, Chinese tea can be divided into six categories, five of which were mentioned just now, and another category is green tea .

The color of tea

The "green" in green tea refers to the color of the tea , which is one of the most important characteristics of tea.

The green color of green tea mainly comes from chlorophyll. Its dry tea can be emerald green, blue green, or dark green, all with green as the main color; the tea soup can be tender green or yellowish green, which is transparent and pleasing to the eye and also presents green elements; the leaf bottom can be emerald green, tender green, blue green, or yellowish green, also with green as the main color.

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In addition to green, dark and black are also important colors of tea . The dry tea of ​​black tea is "dark and moist". This color is the product of the black tea processing process attached to the surface of the tea leaves and appears after drying. Black tea is gray olive to dark brown, because the phenolic substances in the tea leaves are oxidized and acted upon by microorganisms during the fermentation process, producing black-brown pigments.

The taste of tea

People who like to drink tea will emphasize the different flavors of tea. The flavor of tea is the comprehensive response of the human taste organ to the flavor components in tea . In other words, the flavor of tea is the result of the synergistic effect of various flavor components on the human taste organ.

The delicious flavor comes from the coordination of flavor components, but if some components are too much or too little, the coordination of flavor components is destroyed, and the taste is not so pleasant. The flavor components in tea soup can be summarized as sugars, amino acids, phenols and their oxidation products, as well as purine bases, organic acids, tea saponins, etc. The amount of these flavor components and the changes in their ratios have a profound impact on the taste of tea soup.

The "freshness" of tea soup is mainly due to the effects of amino acids (especially theanine), and the amino acid content in green tea is the key to its taste characteristics. The essence of "strong" is that the tea soup has a high content of soluble substances , that is, more water extracts, phenolic substances and their oxidation products and other flavor components; in addition, although pectin is not a flavor component, its high content also gives people a strong taste. "Strong" means "intense", which is mainly the stimulating pleasure brought to people when catechins and their oxides reach a certain content .

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The phenolic substances mentioned repeatedly here play an extremely important role in the taste of tea soup, especially catechins and their oxides. The "astringent" taste also mainly comes from phenolic substances, especially theaflavins. The substances with "bitter" taste include purine bases, especially caffeine, as well as anthocyanins, saponins, etc. Soluble sugars, some amino acids, especially low-molecular amino acids are the elements that produce "sweet" taste. "Sour" substances mainly come from organic acids and some amino acids, especially dibasic amino acids such as glutamic acid and aspartic acid and their amide compounds.

Even for the same type of tea, different picking times and different processing techniques will bring about changes in flavor. This is the beauty of traditional Chinese tea making techniques. We have compiled a flow chart to help you quickly understand the production process of Chinese tea:

Schematic diagram of the production process of Chinese tea. Map: Science Popularization China

You can forward it after seeing this!

Next, we will introduce the historical evolution and production techniques of Chinese tea in detail based on this picture. First, we will focus on the frying of green tea, which is the basis for understanding the tea-making techniques of the other five major categories. This section is quite long. If you already have enough knowledge, you can skip the green tea part and continue reading the evolution of yellow tea, black tea, white tea, black tea, and oolong tea.

green tea

history

Chinese green tea is abundant in quantity and variety. It can be divided into four categories according to the production method, namely fried green tea, baked green tea, steamed green tea and sun-dried green tea . Fried green tea is the most common.

Ru Dunhe of the Qing Dynasty recorded in Yueyanshi: "Tea theory was refined in the Tang Dynasty, and tea affairs flourished in the Song Dynasty. There was no so-called brewing tea. The origin of brewing tea today may not be known, but it existed in the Song Dynasty. And it was started by the Yue people. The name of Chaoqing has been seen in Lu's poems, and Fang Weng's tea tasting in Anguoyuan said... If it is cast on the day, it is Yue tea, not in balls or cakes, but called Chaoqing."

The method of making stir-fried green tea had been perfected in the Ming Dynasty. The method recorded in "Cha Lu" is generally: high temperature killing, rolling, re-stir-frying, and baking until dry . This process is very similar to the modern method of making stir-fried green tea. Since the popularity of stir-fried green tea in the Ming Dynasty, tea people from all over the country have continuously innovated the stir-frying process, and have produced a lot of stir-fried green teas with different appearances and internal qualities. According to the product form, there are long stir-fried green tea (such as eyebrow tea), round stir-fried green tea (such as pearl tea), flat stir-fried green tea (such as Longjing and Qiqiang), etc.

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pick

The representative of flat stir-fried green tea is West Lake Longjing . The earlier the tea is picked, the better. Usually, the Longjing tea picked before Qingming Festival has the best quality, which is called Mingqian tea. The tea picked before Guyu has good quality, which is called Yuqian tea. The picking of Longjing tea also emphasizes tenderness and completeness. Picking only one tender bud is called "lotus heart"; picking one bud and one leaf, the leaf is like a flag and the bud is like a gun, which is called "flag gun"; picking one bud and two leaves, the leaf shape is like a sparrow tongue, which is called "sparrow tongue". Usually, to make 1 kilogram of special-grade Longjing tea, 70,000 to 80,000 tender buds and leaves need to be picked. The picking standard is one complete bud and one leaf, the bud is longer than the leaf, and the total length of the bud and leaf is about 1.5 cm.

For a long time, the timely picking system has been passed down from generation to generation. It is customary to pick the big ones and leave the small ones according to the standard. Generally, the early spring tea is picked every day or every other day , and the middle and late spring tea must be picked every few days. Therefore, about 30 batches of tea are picked during the annual tea production season. Early, tender, and diligent are the three major characteristics of Longjing tea picking.

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The picked fresh leaves need to be spread thinly indoors in order to emit the grassy scent, enhance the tea aroma, reduce the bitterness, increase the amino acid content, and improve the freshness; it can also make the fried Longjing tea smooth in appearance, emerald green in color, and not clump.

After 8 to 10 hours of spreading, the fresh leaves are screened and divided into three grades : large, medium and small , and fried separately. In this way, different grades of raw materials can be fried at different pan temperatures and with different hand gestures to achieve the perfect result.

Stir-fry

High-grade Longjing tea is made by a pair of hands in a smooth special iron pot, constantly changing the techniques. The frying techniques include shaking, placing, collapsing, pressing, throwing, grabbing, pushing, pressing, pressing, grinding, etc., which are known as the "Ten Techniques". When frying, the techniques are constantly changed according to the size of the fresh leaves, the degree of maturity and the degree of formation of the tea leaves in the pot , which is very clever.

The frying process is divided into three steps: green pot, moisture recovery, and huī pot . Green pot is the process of killing the green leaves and preliminary shaping. When the pot temperature reaches 80-100℃, a little oil is applied to make the pot surface smoother, and about 100 grams of leaves that have been spread out are put in. Start by grabbing and shaking the leaves. After a certain amount of moisture is released, gradually change to using the hand techniques of placing, pressing, shaking, and throwing to perform preliminary shaping. The pressure is from light to heavy to achieve the purpose of straightening into strips and flattening into shape. When the leaves are 70% to 80% dry, remove them from the pot. It takes about 12 to 15 minutes.

After taking it out of the pot, spread it thinly to regain moisture. After cooling, it is sieved. The sieved bottom tea and sieved surface tea should be simmered separately. The cooling and regaining moisture time is generally 40 to 60 minutes.

The purpose of the pot is to further shape and dry the tea leaves. Usually, four pots of green pot leaves are combined into one pot, and the amount of leaves is about 250 grams. The pot temperature is 60-70℃, and it needs to be fried for 20-25 minutes. The pot temperature is controlled in the process of low, high, and low. The hand pressure gradually increases, mainly using grasping, buckling, grinding, pressing, pushing and other techniques. The key is to keep your hands on the tea leaves and the tea leaves in the pot. Fry until the hair falls off, the leaves are flat and smooth, the tea fragrance is revealed, and they break easily when bent. The water content is 5-6%, which is appropriate. Then you can remove the pot, spread it out to cool, and sift out the yellow flakes and the tea residue.

Collect ash

The roasted Longjing tea is very easy to be affected by moisture and deteriorate. It must be wrapped in paper into 0.5 kg bags in time, placed in a jar with block lime (lime that has not absorbed moisture and weathered) on the bottom, and sealed and stored. This is commonly known as "collecting lime". If stored properly, after about 0.5 to 1 month, the aroma of Longjing tea will be more fragrant and the taste will be more fresh and refreshing. Longjing tea that is kept dry can still maintain its green color, high fragrance and mellow taste after being stored for a year .

Yellow Tea

If the green tea frying process is not properly mastered, such as low frying and killing temperature, too long steaming and killing time, or not timely cooling and rolling after killing, or not timely drying and frying after rolling, or stacking for too long, the leaves will turn yellow, and green leaves and green soup will not be produced, but yellow leaves and yellow soup will be produced, similar to the yellow tea that appeared later. Therefore, the emergence of yellow tea may have evolved from the improper mastery of green tea making methods .

The history of this evolution was also recorded in the Ming Dynasty’s Tea Commentary (1597): “But the people in the mountains are not good at making tea. They roast it in a pot with firewood. Before it is out of the pot, it is already burnt and withered. How can it be used? They also make huge bamboo tubes to store it while it is hot. Although there are green branches and purple shoots, they will soon wither and turn yellow. It is only good for eating, not for tasting.”

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Modern yellow tea is a lightly fermented tea, and its basic process is similar to that of green tea , but it is fermented to yellow during the tea-making process, so it has the characteristics of yellow soup and yellow leaves. Take Junshan Yinzhen as an example, it is harvested about three days before the Qingming Festival, and has eight processes: killing the green, cooling, initial baking, initial packaging, re-baking, cooling, re-packaging, and full-fire.

Yellow tea, green tea, and black tea all have a common feature in the manufacturing process, that is, after the fresh leaves are picked and properly spread out for storage, they must be sterilized at high temperatures to completely destroy the activity of enzymes. After sterilization, the oxidation of polyphenol compounds is caused by non-enzymatic auto-oxidation caused by the effects of moisture and heat. At the same time, other chemical substances in the tea also undergo corresponding changes.

Before drying, yellow tea is manufactured under different process conditions from green tea and black tea, and the degree of moisture and heat effect varies. The depth and breadth of oxidation of polyphenolic compounds are also different. The degree of change of green tea is slight, the degree of change of black tea is severe, and the degree of change of yellow tea is in between the two . From this perspective, yellow tea is a transitional tea between green tea and black tea. From the color of dry tea, it forms a continuous color spectrum from green to yellow to dark brown.

Black Tea

When green tea is withered, the leaves are abundant and the fire temperature is low, which changes the leaf color to a dark brown-green color that is almost black. Or the green raw tea is piled up and fermented to turn black, which is the process of producing black tea.

Dark tea is a post-fermented tea . As early as the 11th century, there were records of using green tea to make it darker. In the third year of Jiajing in the Ming Dynasty (1524 AD), the imperial censor Chen Jiangshu recorded the production of dark tea. At that time, the dark tea produced in Anhua, Hunan was mostly transported to border areas to exchange horses. The fresh leaf raw materials are based on new shoots and green stems, and one bud and one or two leaves are not picked. The fresh leaf raw materials are generally divided into four levels. The first level is mainly based on one bud and three or four leaves, the second level is mainly based on one bud and four or five leaves, the third level is mainly based on one bud and five or six leaves, and the fourth level is mainly based on the pinned shoots.

The manufacturing process of black tea is divided into five steps: withering, initial rolling, pile fermentation, re-rolling and drying .

White Tea

The so-called white tea in the Tang and Song dynasties refers to the tea made from white-leaf tea trees that were discovered by chance. Song Huizong Zhao Ji's "Daguan Tea Theory" stated: "White tea is a kind of its own, different from ordinary tea. Its stripes are spread out, and its leaves are thin and shiny. It grows occasionally between cliffs and forests. Although it is beyond human control, there are only four or five families who have it, and only one or two plants growing...so white tea became the best." This kind of white tea is different from the white tea that was developed later and is made without frying or kneading.

Modern white tea gradually evolved from the three-color fine buds and silver-threaded water buds of green tea in the Song Dynasty. Initially, it referred to the "white hair silver needle" with dense white hairs on the surface of dry tea and silvery white color . Later, it developed into different colors such as white peony, tribute eyebrow and Shoumei . White tea is made from the buds and leaves of the big white tea tree. The big white tea tree was first discovered in Zhenghe, Fujian. It is said that it was accidentally discovered by farmers during the Xianfeng and Guangxu periods. This tea tree has large buds and many hairs. It is dried in the sun and has a good fragrance.

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Silver Needle Baihao is picked when it is the tender spring tea shoot with one bud and one leaf, and then the true leaves and fish leaves are gently peeled off with fingers. The peeled tea buds are evenly spread on the water sieve without overlapping, placed in weak sunlight or ventilated shade, and dried in the sun until 80% to 90% dry, and then roasted in a roasting cage at 30-40℃ until fully dry. Some people use the hot sun instead of roasting cages to dry completely, which is called hair needles. Hair needles are sieved to pick fat and long tea buds, and then the stems are manually picked (commonly known as silver needle feet), and the leaves, debris, impurities, etc. are sieved to remove, and finally roasted with a slow fire and packed while hot.

black tea

In the process of tea manufacturing, it was discovered that sun drying replaced withering , and the leaves turned red after rolling, which resulted in black tea. The earliest black tea production began with the small-leaf black tea in Chong'an, Fujian. Liu Jing of the Qing Dynasty recorded in "A Collection of Leisurely Notes" (1732): "There is a town called Xingcun at the end of the ninth bend of the mountain, which is the most popular among experts. In addition, there are teas produced in Shaowu, Jiangxi Guangxin and other places, which are black and red in color, and are locally called Jiangxi Wu, and are all sold privately in various businesses in Xingcun." After the creation of Xingcun Small-leaf Black Tea, it gradually evolved into Gongfu Black Tea. Therefore, Gongfu Black Tea was founded in Fujian and later spread to Anhui, Jiangxi and other places.

The black tea produced in Qimen, Anhui Province was brought to his hometown by Yu Ganchen, who was dismissed from office in Fujian in 1875 and brought the Fujian black tea-making method with him. He set up a black tea shop on Yaodu Street in Zhide and successfully trial-produced the tea. The following year, he set up a branch shop in Likou, Qimen for trial-production, and gradually expanded production, thus creating the famous "Qimen Gongfu" black tea.

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Black tea is a fermented tea , and the basic process is withering, rolling, fermentation, and drying . There are many types of black tea in China, and the production areas are wide. There are China's unique Gongfu black tea and Xiaozhong black tea , as well as broken black tea similar to India and Sri Lanka. Their production methods are similar. Among them, Xiaozhong black tea has the red pot (killing) process of oolong tea. The quality characteristics of various black teas are red soup and red leaves, and the formation of color, aroma and taste has similar chemical change processes, but there are differences in the conditions and degree of change.

Oolong Tea

There is still controversy in the academic community about the origin of oolong tea. Some infer that it appeared in the Northern Song Dynasty, while others presume that it began during the Xianfeng period of the Qing Dynasty (1851-1861 AD), but all believe that it was first created in Fujian.

Regarding the production of oolong tea, according to historical records, Wang Caotang's "Tea Theory" quoted in Lu Tingcan's "Continuation of the Classic of Tea" in the Qing Dynasty: "Wuyi tea... After the tea is picked, it is evenly spread in bamboo baskets and placed in the sun to dry in the sun. When the green color gradually fades, it is fried and roasted... Only Wuyi uses both frying and roasting. When it is cooked, it is half green and half red. The green is the fried color, and the red is the roasted color. The tea is picked and spread, and then spread and picked. It is fried as the aroma begins to develop. It is not acceptable to fry it too late or too late. After frying and roasting, the old leaves and branches are picked out to make it one color." "Tea Theory" was written in the early Qing Dynasty. That is to say, the unique craftsmanship of Wuyi tea was formed before the early Qing Dynasty.

Today, the production method of Wuyi Rock Tea in Chong'an, Fujian Province still retains the characteristics of this traditional oolong tea process. The main process procedures include withering (drying the tea leaves), shaking the tea leaves, cooling the tea leaves, frying the tea leaves, roasting the tea leaves and picking the tea stems . Drying the tea leaves refers to "after picking the tea leaves, evenly spread them in bamboo baskets and place them in the sun, which is called sun drying the tea leaves". Shaking the tea leaves refers to "spreading and shaking them". Shaking means shaking, that is, shaking the tea leaves after drying them. The alternation of shaking the tea leaves and cooling the tea leaves is the current method of making tea leaves. When the tea leaves are made to a certain degree, "wait until the green color gradually fades, then stir-fry and roast them", and after roasting, "pick out the old leaves and branches to make them one color".

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"Stir-frying and roasting" is the key to the production process of oolong tea, that is, its production process is much more complicated than that of black tea and green tea. Oolong tea absorbs the manufacturing principle of black tea fermentation and green tea non-fermentation. The manufacturing process does not completely damage the entire leaf tissue , but slightly scratches the leaf edge tissue. It requires that the cell contents are not completely changed , but a part of them is oxidized, which triggers a unique color, aroma and taste. This is the so-called "semi-fermented" tea.

So, what kind of Chinese tea do you like best?

Author｜Nothing Can Break Up

Review | Ruan Guangfeng Director of Science and Technology Department of Kexin Food and Nutrition Information Exchange Center

Yu Liangzi Senior Laboratory Technician, Tea Research Institute, Chinese Academy of Agricultural Sciences

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