Analysis on the Characters of Dark Tea in Different Producing Areas Based on Sensory Evaluation

Jing HUANG Hai LIN Changhui HE Xuchao YAN Fen YUAN Xia PENG

Abstract Sensory evaluation is an important way for evaluating the quality of tea. By sensory evaluation, we can judge and identify the quality, distinguish the types, and characterize unique qualities of dark tea, in order to offer technical guidance for producers and give references to consumers. In this paper, we mainly summarized the requirements and methods of dark tea evaluation, expounded the characteristics in main producing areas, and analyzed the key process characteristics and the main technology that affecting the quality formation of dark tea.

Key words Evaluation of dark tea; Sensory evaluation; Dark tea quality characteristics

Received: January 3, 2021  Accepted: March 5, 2021

Jing HUANG (1984-), female, P. R. China, engineer, master, devoted to research about tea quality safety.

*Corresponding author. E-mail: 272078352@qq.com.

Dark tea is one of the six basic teas classified by color. Most of them are compressed tea undergone reprocessing tea, also known as brick tea. Because of its complicated processing technology and "color turning by pile fermentation", its quality formation is the most complicated, and it belongs to "post fermented" tea. The raw materials used in dark tea are relatively mature and the ingredients are complex. Generally, the processing of dark tea requires primary processing, re-processing, refining and pressing, and also requires storage of "ageing, ripening" and other processes. Its production and marketing cycle is the longest, commonly known as "the more mature the better", and its quality transformation is profound. The dry tea obtained is dark in color and dark (or yellow) brown, oily, mellow and smooth in fragrance, and the tea soup is yellow-orange to orange-red, and the leaves at the bottom are black. Dark tea belongs to the unique tea category in China［1］ with a long history of production and sales, a wide production and sales area, and a large consumption, and has been a daily necessity for Chinese ethnic minorities in the past. Nowadays, black tea has attracted the attention of tea drinkers due to its "digestion-promoting, anti-greasy, and blood pressure- and blood lipid-lowering" effects. The production and sales of black tea show recovered growth, and it has started to be sold in a large quantity in domestic market, and is even exported abroad, with broad market prospects.

The black tea preparation method was formed earlier, second only to green tea. In the fifteenth year of Tang Zhenguan (711), "tea came to Tibet from Princess Wencheng" (according to the Appendix of Tibetan Political and Educational Book); in the Five Dynasties, "there was Huofanbing..., entered Xifan and Dangxiang" (the Five Dynasties, Tea Book of Mao Wenxi); and in the third year of Song Xining (1 070), a "horse buying farm" was set up at Diaomen, Yazhou, Sichuan, which was the first tea-horse exchange market. In the 7th year of Xining (1074), the "Tea Horse Division" was established in famous mountains in Sichuan, and to the 12th year of Yuan Zhiyuan (1275), the tea shipped and sold in Tibetan areas was collectively referred to as "Xifan Tea" (according to The History of the Yuan Dynasty. The Book of Renzong); and during this period, due to the long shipping and marketing time of compressed tea (brick tea), the long journey, or the "natural fermentation" by the sun and rain, the color and taste of dark tea has begun to form. Around the 11th century, Sichuan Tianquan produced the "Wu tea" production method, and there appeared "setting frame and packaging" and "pressing Zeng tea". Specifically, sun-dried green primary tea was wet-fermented in piles (about 20 d) for changing its color and autoclaved to lump tea. Such method is the preparation of black tea at the early stage. After the 16th century, for Anhua black tea, the primary tea was kneaded and piled for more than 20 h, fried and dried after color turning, and then made into compressed tea in blocks, brick cakes, etc., through blending, steaming, building and pressing, baking, etc., thus forming the black tea initial processing and pressing technology. At the end of the Ming Dynasty, there appeared "Miebao tea" which was quantitatively built to a tight state. After the late Ming, Qing Dynasty and the Republic of China, the black tea production method has been continuously improved, and the products have become more abundant. The production and sales area has gradually expanded to Sichuan, Hunan, Shaanxi, Hubei, Yunnan, Guangdong, Guangxi and other provinces; and regional dark tea products have gradually formed, with Hunan dark tea, Hubei Laoqing tea, Sichuan Bian tea, Guangxi Liubao tea, Yunnan Puer tea［2］, and Jingyang Fu tea as representatives. The pattern and quality characteristics of dark tea from different origins have their own characteristics. In this study, with the dark tea sensory evaluation technology as a carrier, the unique qualities of dark tea from different producing areas were distinguished and summarized, hoping to provide consumers with a preliminary reference for basic appraisal and identification of dark tea quality.

Black Tea Examination and Evaluation

Tea sensory evaluation is a traditional technical method in which the priority, level and grade of tea quality is evaluated through the senses of professional and technical personnel. It is simple, practical, and effective, and is often used to judge the quality of tea produced and put into the market. Specifically, a comprehensive, objective, fair and scientific quality evaluation is performed on such four appearance quality item as shape, color, wholeness, and clarity of the tea and such four internal quality items as the aroma, taste, soup color, and flavor of the tea depending on the sense organs such as the vision, smell, taste, and touch organs by tea-evaluation terms or scoring methods［3］. The accuracy of such evaluation method is based on the condition that the tea-tasters obtain sensitive organs through their solid tea evaluation knowledge and skills and training of the normal sensory system, become familiar with the quality characteristics of various teas, and operate according to tea sensory evaluation standards and technical specifications. For example, well-trained tea-tasters can use the senses to more accurately evaluate the quality characteristics of dark tea and identify the type of producing areas.

For the sensory evaluation of the quality of dark tea, in addition to the tea-tasters who should be familiar with the quality characteristics of various dark teas and operate in accordance with relevant national standards, the evaluation site should also meet the basic requirements of the tea sensory evaluation rooms, so the outdoor environment and internal conditions of evaluation rooms and the tea evaluation ware must meet the requirements［4］. The basic conditions are mainly based on the GB/T 18797-2012 General requirement of the tea sensory test room［5］, and the evaluation method is to determine the sensory quality of dark tea objectively based on the Methodology of sensory evaluation of tea (GB/T 23776-2018)［6］ formulated by the state, combining with GB/T 14487 The terms of tea sensory tests［7］.

According to the national standard GB/T23776, dark tea evaluation items (scoring coefficient) are divided into: shape (30 points), soup color (10 points), aroma (20 points), taste (25 points) and bottom leaves (15 points). The shape of loose black tea is evaluated on the strips, tenderness, color and purity. For the strips of Puer, Xiangjian, Tibetan tea and Liubao tea, the compactness of the strips and whether they are in strips are evaluated; and for the appearance of the compressed black tea, items such as evenness, tightness, tenderness, color and purity are evaluated, of which the evenness means that the tea has correct shape, neat edges and corners, clear pattern, and no layering, and the tightness refers to the overall thickness and size are consistent. The tenderness depends on the tightness and whether the tips or the stalks and leaves are old or tender; the color depends on the degree of oily black; the purity depends on the content of the stalks, slices, ends, seeds and other non-tea inclusions; Fu brick is commented on the growth status of "Eurotium cristatum", and the blooming flowers should be lush, common, and large in size; and as to the tightness, black brick, Qing brick, Mi brick, and Hua brick are better to be autoclaved to make the surface smooth, and Fu brick, cake tea, and Tuo tea should not be too tight, and should have moderate elasticity. When evaluating the color and luster of dry tea, as far as the new teas pressed within 3 years are concerned, Puer should be reddish brown, Xiangjian should be black, Jinjian is generally pig liver color, Jin tea is required to be oily, cake tea should be dark and oily, Fu brick should be yellow-brown, and Kang brick should be tan. From the perspective of the internal quality, the color of soup is commended on redness and brightness. For compressed teas, Hua brick should be orange, Puer Tuo tea should be orange and bright, the Fangbao should be brown-red, Kang brick and Fu brick are normal in orange or orange red, and Jinjian is normal in red with brown. Aroma: Mi brick and Qing brick have a smoky smell, which is a disadvantage, but it is normal for Fangbao tea to have a burnt smoky smell. The taste evaluation focuses on whether there are green, astringency, rancidity and mildew tastes. Color of bottom leaves: The dark brown of Kang brick is normal, and the tender yellow of Jin tea and cake tea is better. Stem content: Mi brick does not contain stalks, but Qing brick, Fu brick, black brick, Hua brick, Jin tea, Kang brick, and cake tea are allowed to contain a certain percentage of tender stalks in the past year according to the quality standards, and must not contain old stalks of the former year.

Jing HUANG et al. Analysis on the Characters of Dark Tea in Different Producing Areas Based on Sensory Evaluation

The Distribution and Quality Characteristics of Chinese Dark Tea

Dark tea belongs to post-fermented teas［8］. For the dark tea of traditional crafts, first of all, the raw material has a certain degree of maturity, and in processing, the fresh leaves are subjected to deactivation of enzymes, initial kneading, and initial pile fermentation. After being pressed into a finished tea, it undergoes deep pile fermentation again. The tea undergoes several times of fermentation, and the obtained tea has the longest fermentation time and deepest fermentation degree among the six major teas. In addition, the finished tea (or compressed tea) is still fermented in storage, so it is called "post-fermented" tea. Pile fermentation is a key process for the formation of black tea and also a key process for the discoloration of black tea. At this stage, dark tea is subjected to moderate fermentation based on the tenderness of the leaves.

Chinas main black tea distribution areas

Black tea is divided into primary tea and finished tea. After being refined, black primary tea is processed into reprocessed tea, which is divided into brick tea, block tea, basket tea, and granular tea.

Hunan black primary tea is generally made from fresh leaves with one bud and four and five leaves as raw materials, and is prepared through five processes including deactivation of enzymes, initial kneading, pile fermentation, re-kneading, and drying［9］. Hunans finished black tea is mainly classified into "three Jian", namely Tianjian, Gongjian, and Shengjian, "three bricks", namely black brick, Hua brick, and Fu brick, and the "Yihuajuan", i.e., Qianliang tea, which can be divided to Shiliang tea, Bailiang tea and Qianliang tea based on its specification. Qianliang tea is also a special dark tea in Hunan, enjoying the reputation of "the worlds tea king", and its processing skills have been listed as Chinas intangible cultural heritage.

Hubei Laoqing brick, also known as "Laoqing brick" and "Chuanzi Tea"［10］, is mainly produced in Chibi and Chongyang in Xianning City, Hubei Province. The main process is to perform Shaiqing first, followed by pile fermentation, and drying into the primary black tea, which is then pressed into the finished product.

Sichuan Bian tea is divided into Nanlu Bian tea and Xilu Bian tea according to the different sales routes. The Nanlu Bian tea is mainly manufactured in Yaan. The production areas include 4 counties and cities, namely Yaan, Yingjing, Tianquan, and Mingshan, which are the main producing areas, and the products are exclusively sold in Xikang and the Tibet region, and have also become "Tibetan tea". The Xilu Bian tea is made at Dujiangyan as its manufacturing center. The raw materials are mainly produced in Guanxian, Chongqing, Dayi, Beichuan and other places, and the products are exclusively sold in Songpan, Li County, Mao County, Wenchuan and parts of Gansu. At present, Fu brick and Fang brick are mainly produced.

Guangxi Liubao tea is named because of being produced in Liubao Township, Cangwu County, Guangxi. At present, besides Cangwu as the main producing area, He County, Lingxi, Heng County, Yulin, Lingui, Xingan and other places also produce the tea in a certain scale.

Yunnan Puer tea is produced in Xishuangbanna, i.e., Simao and other places in Yunnan Province. It is named "Puer tea" because it is processed and sold in Puer City. According to the national standard Product of geographical indication-Puer Tea (GB/T 22111-2008), Puer tea is defined the product processed with Yunnan arbor and big-leaf Shaiqing tea within the scope of protection of geographical indications as the raw material by specific processing technologies within the protection scope of geographical indications, which has its unique quality characteristics. According to its processing technology, Puer tea is divided into two types: raw Puer tea and ripe Puer tea. The raw Puer tea belongs to green tea, and the ripe Puer tea belongs to dark tea.

Jingyang County, Shaanxi Province is the cradle of Fu tea［11］. However, Shaanxi belongs to the northwest region and is not suitable for the growth of tea trees. Therefore, the local area does not produce tea. The reason is that this place is an important trade and sales area on the historical Silk Road. Especially in the middle of the Tang Dynasty, it was a prosperous place for tea-horse trade between the mainland and Beyond the Great Wall. The raw materials for making Fu tea here are mainly from Anhua, Hunan, and they are transported to Jingyang, Shaanxi via land transportation (the ancient tea-horse road) and water transportation (Zishui). Because of the exquisite craftsmanship at the time, the pressed Fu tea must be pressed in the dog days, and was also called "Fucha" at first. Because of its unique quality characteristics, Fu tea is loved by the people in the northwest and Beyond the Great Wall, and the local production is difficult to meet the market sales. Later, under the guidance of technicians, through repeated trials and explorations, it was successfully transferred to Anhua, Hunan for large-scale processing and production. Nowadays, Jingyang still produces Fu tea, and with the attention and support of the local government, it has formed a certain scale.

Description of the Quality Characteristics of Black Tea in Various Regions of China

Tea has a very obvious regional nature. The quality characteristics of tea from different producing areas are different due to the local soil, climatic conditions, light intensity, and tea varieties and processing techniques. Through sensory evaluation, the quality characteristics of various black tea products from various producing areas were summarized. Hunan "Xiangjian tea" refers to Tianjian (Xiangjian No.1), Gongjian (Xiangjian No.2), and Shengjian (Xiangjian No.3)［12］. Its quality characteristics are: tight and heavy strips, dark brown and oily color, pure inner aroma with pine smoke flavor, orange-yellow soup, refreshing, sweet and smooth taste, and yellowish brown, soft and even bottom leaves. As to the "three brick tea", the quality characteristics of Hua brick are: flat brick surface, distinct edges and corners, clear patterns, yellow, brown and oily color, pure inner aroma with pine smoke flavor, mellow taste, orange-yellow soup, and russet tender bottom leaves. The quality characteristics of black brick tea are: flat brick surface, distinct edges and corners, yellowish brown and oily color, pure inner aroma, bright orange-yellow soup, mellow and slightly astringent taste, and yellowish brown, stretched and still tender bottom leaves. The Fu brick tea is a special tea of Hunan black tea, originated from Jingyang County, Shaanxi Province, and currently, there are three main types of mechanical pressed, hand-built, and Fu tea in bulk. The quality characteristics of Fu brick tea are: flat brick surface, distinct edges and corners (mechanism), uniform thickness, yellow-brown or dark-brown tea color, pure internal aroma, rich scent of fungi, orange-yellow or orange-red bright soup, pure taste and no astringency. The quality characteristics of Qianliang tea are: dark brown tea appearance, cylindrical, compactly pressed, no honeycomb shape, tightly knotted or in the shape of "Jinhua", orange or orange red soup color, pure aroma with pine smoke flavor and Junhua scent. Anhua Qianliang tea of more than ten years has an aging fragrance, a mellow taste. The new tea is slightly astringent. Anhua Qianliang tea over 5 years has a mellow, sweet and moist taste, and dark brown, tender and even and more complete leaves.

Most of Hunan dark tea is produced in Anhua, Hunan. Professor Cai Zhengan defines it in "Hunan Dark Tea": The raw materials of dark tea are picked from the large and middle-leaf population varieties of the Xuefeng Mountains, and are subjected to deactivation of enzymes, rolling, pile fermentation and drying by the open flame of Songcai, giving the product which has dark brown oily color, mellow taste, red and bright soup, and Hunan dark tea is a collective term for the primary tea with a unique quality characteristic of slight pine smoke scent and the compressed tea prepared taking it as the raw material by autoclaving. It has the characteristics of big and thick leaves, thick soup, and good soaking tolerance［13］. The uniqueness of Hunan black tea is that it uses local pine wood or tree base to slowly dry the material over the open flame in a Qixing stove, and Hunan black tea thus has a unique quality characteristic of pine smoke scent. At present, due to the promotion of green development and the protection of forests, most companies use environmentally friendly charcoal for baking, and the quality of tea shows a clear "fire-roasting fragrance".

The quality characteristics of Hubei Qing brick are flat brick surface, distinct edges and corners, yellowish brown and oily (or still color) color, pure internal quality aroma, yellow-green (or deep yellow) soup, mellow and slightly astringent taste, and yellowish brown, spread and still tender bottom leaves. Hubei Laoqing brick adopts kneading and sun-drying in combination with the traditional black tea processing technology. The fresh leaves are subjected to deactivation of enzymes, first kneading, preliminary sun-drying, and then re-frying, that is, after the cells are broken, they are subjected to a day of fermentation, stopping of the fermentation, re-kneading, and then enter the deep pile fermentation, forming the unique mellow quality of Hubei Laoqing brick.

The quality characteristics of Sichuan Bian tea are rough and old leaves rolled into strips, brown dry tea in a color like pig liver, pure internal quality aroma, red and bright soup, mellow and smooth taste［14］, and brown bottom leaves. The raw material of Xilu Bian tea is thicker and older than that of the Nanlu Bian tea, and contains more stalks, so it is in a withered yellow color［15］. Sichuan Bian tea is also called "Tibetan tea" because it is mainly sold in Tibet. The processing technology of Tibetan tea is extremely meticulous, and can be subdivided to 32 procedures, and the initial processing has the characteristics of three kneading and three steaming, leading to an aged and mellow taste.

The quality characteristics of Liubao tea are well-known for the four unique characteristics of "red, thick, mellow, and aged". The specific quality characteristics are thick, long and unbroken strips, black and shiny color, aged and mellow aroma in the internal quality with pine smoke scent, red and bright soup color, sweet and mellow taste with pine smoke and betel nut flavor, and copper-brown and relatively complete bottom leaves. The traditional Liubao tea production process is characterized by two times of high-temperature steaming and two times of "pile fermentation", that is, "double steaming and double pile fermentation". The modern technology is: primary black tea-adding water to humidify-stirring evenly-pile fermentation-high temperature steaming-basketing-aging-Liubao black tea. Among them, the process of "pile fermentation and aging" is the key to the unique quality of Liubao black tea［16］, which promotes the full conversion of tea polyphenols in tea to form a soup with a rich red color, a mellow taste, and a unique betel nut aroma.

Puer black tea (ripe tea) is divided into 11 grades, including special grade, grade one to grade ten, according to its quality. The overall quality characteristics include are stout, strong and heavy appearance, dark brown or maroon color (pig liver or off-white), thick red or brown soup, unique aroma, aging fragrance, mellow and sweet taste, and thick and maroon bottom leaves［17］. Most of the tea trees in Yunnan are large-leaf species, with the characteristics of tall trees, and large and stout leaves. Due to the long-term warm temperature and long sunshine time, combined with the drying process in the traditional Puer tea processing technology, oven drying and sun drying are combined, so Puer tea has its unique "Yunnan flavor" quality characteristic.

Jingyang Fu tea is made from high-quality Anhua primary black tea through re-fermentation and fungal growing process. Because it has a special kind of fungus that is beneficial to the human body, "Coronatus cristatum", commonly known as "Jinhua". Its quality characteristics are similar to those of Anhua Fu Tea, specifically: the soup is bright orange-yellow or orange-red, not turbid, the fungal fragrance is obvious, and the taste is mellow, not astringent. Nowadays, Fu tea is deeply loved by consumers because of its unique "fungal flavor", as well as its effects of human metabolism regulation, health care and disease prevention. Dark tea, as one of the six major teas (except for reprocessed tea), has its unique quality characteristics due to the exquisite raw materials and the complexity of the process. Familiar with the technical characteristics and main quality characteristics of dark tea in various places is the basis for tea-tasters to do a good job in the quality identification of dark tea. Meanwhile, their understanding in the quality characteristics of dark tea in various regions can provide consumers with a basic reference when purchasing dark tea. Furthermore, the identification of the quality of dark tea through tea-tasters can also provide a certain quality reference for the production of dark tea.

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