A Detailed Explanation of the Manufacturing Process of Nanlubian Tea

Nanlubian Tea is a type of compressed tea produced in Sichuan and sold exclusively to Tibetan areas. In the past it was divided into six varieties: Maojian, Yaxi, Kangzhuan, Jinyu, and Jincang; now it has been simplified to two varieties: Kangzhuan and Jinjian. It was formerly mainly produced in the Ya'an and Leshan regions, and has now expanded to tea areas throughout the province. It is centrally processed at state-owned tea farms (factories) in Ya'an, Yibin, Chongqing, Wanxian and other places.

The raw materials of Nanlubian Tea are coarse and old and include a portion of tea stems. Because of different fresh leaf processing methods, the crude tea is divided into two types: that which is directly dried after fixation without steaming and rolling is called "Maozhuang tea" or Jinyu tea; that which is steamed and rolled multiple times and pile-fermented and then dried after fixation is called "Zuozhuang tea." Maozhuang tea, because of its simple preparation method and poor quality, has been eliminated.

The primary processing of Nanlubian Tea is rather complicated. The traditional method for Zuozhuang tea involved as many as 18 steps at most: one pan-firing, three steamings, three treadings, four pile-fermentations, four sun-dryings, two pickings, and one sifting; at minimum it required 14 steps. Since the 1960s, through continuous improvement, the new process has been simplified to 8 steps. The traditional process and the new process for Zuozhuang tea are described separately below.

(1) The Traditional Process for Zuozhuang Tea

The manufacturing steps for Zuozhuang tea are, in order: fixation, first pile-fermentation, first sun-drying, first steaming, first treading, second pile-fermentation, first picking, second sun-drying, second steaming, second treading, third pile-fermentation, repeat picking, third sun-drying, sifting, third steaming, third treading, fourth pile-fermentation, fourth sun-drying.

① Fixation. The traditional fixation method uses a large No. 93 cm diameter pan for fixation, with 15-20 kg of leaves added each time. Before adding the leaves, the pan temperature is about 3000C. The method is to first closed-fry, then stir-fry, combining turning and covering, with covering as the main method. The time is about 10 minutes, and the fresh leaves lose about 10% of their weight. Now the Chuan-90 type fixation machine is generally used for fixation, with a pan temperature of 240-260°C, a leaf load of 2025 kg, and closed-frying for 7-8 minutes. When the leaf surface loses its luster, the leaf texture becomes soft, the stems bend without breaking, and a tea aroma is given off, it can be removed from the pan.

② Piling. Piling means pile-fermentation. Its purpose is to make the tea material pile up and generate heat, promote the non-enzymatic auto-oxidation of polyphenolic compounds, change the leaf color from green to yellow-brown, and form the unique quality of Nanlubian Tea. Piling is an important step in making Zuozhuang tea; at most it is carried out four times, and at least three times. The first piling is after fixation; the fixed leaves should be piled while hot, for 8-12 hours, with the pile temperature maintained at about 60°C, until the leaf color turns light yellow. After each subsequent steaming and treading, piling must be carried out, for 8-12 hours, to remove the green and astringent taste and bring out the aged tea aroma. When the leaf color turns dark red-brown and water droplets appear on the surface of the pile, the pile can be opened. If the leaf color is too light, the last piling time should be extended until it meets the requirements, and then it is sun-dried.

③ Steaming. The purpose is to increase the toughness of the leaves after heating, making it easier to remove stems and roll the leaves into strips. The method is to put the tea material into a steaming barrel and place it over an iron pan with boiling water to steam the tea. The steaming barrel used for steaming tea is commonly called a "zeng." Its upper diameter is 33 cm, lower diameter 45 cm, and height 100 cm, and each barrel holds 12.5-15 kg of tea. Steam until water droplets drip down from the conical bamboo-hat-shaped steam cover, the tea material in the barrel sinks, and the leaf texture becomes soft.

④ Treading. Pour the steamed tea material while hot into hemp bags, tie the bag mouths tightly, and two people each lift one end of the hemp bag and place the tea bag on the upper end of the treading board. Then the two people stand side by side on the tea bag and tread it with their feet from top to bottom, making the tea bag roll and prompting the tea material to tighten and roll into strips. The two people's steps must be in unison and their force even; the tea bag should roll slowly, and not too fast. The treading board is made of wooden boards 6-7 cm thick, about 6 m long and about 1 m wide, installed at a 30-degree slope, with bamboo poles placed on both sides as handrails to facilitate operation. Steaming and treading are closely connected; generally it is three steamings and three treadings, and at minimum two steamings and two treadings.

⑤ Stem picking and sifting. After the second and third pile-fermentations, stems are picked once each time. According to the specified stem quantity standard, all long stems over 10 cm must be picked out cleanly. After the third sun-drying, sifting is carried out to separate the coarse and fine parts, which are then steamed, treaded, and pile-fermented separately, and then sun-dried.

⑥ Sun-drying. After each pile-fermentation, the tea material must be spread out for sun-drying. The spreading thickness is 6-10 cm, and it should be turned frequently to strive for uniform dryness. After each sun-drying, the tea material must be moved indoors and spread for one to two hours, so that the moisture within the leaves is redistributed evenly before the next steaming and treading can be carried out. If the tea material is unevenly dry and wet, the moisture content after steaming will also differ, and the leaves are easily broken during treading. Proper dryness in spread sun-drying is one of the keys to making good Zuozhuang tea, and the dryness of each step must be carefully controlled. According to experiments, the first sun-drying should be to 60% to 65% dry (moisture content 25-35%), the second to 70% to 75% dry, the third to 75% to 80% dry, and the last to 85% to 90% dry, with the crude tea moisture content at 10-14%.

(2) The New Process for Zuozhuang Tea. This new process is the result of joint research in the late 1960s by units such as the Ya'an Tea Factory and the Mengshan Tea Farm.

The manufacturing steps of the new process are, in order: steaming fixation, first rolling, first picking, first drying, second rolling, pile-fermentation, repeat picking, and full drying.

① Steaming fixation. Steaming fixation means using steam for fixation. That is, put the fresh leaves into a steaming barrel and place it over a boiling water pan to steam. When steam emerges from the cover opening and the leaf texture becomes soft, it is ready; the time is about 8-10 minutes. If steamed on a boiler steam generator, it takes only 1-2 minutes.

② Rolling. Rolling is carried out in two stages, and machine rolling is now promoted. After the fresh leaves are fixed, roll them while hot for the first rolling, with the aim of separating the leaf blades from the tea stems, without applying pressure, for 1-2 minutes. After rolling, the moisture content of the tea material is 65-70%. After first drying, the moisture content is reduced to 32-37%, and the second rolling is carried out while hot, for about 5-6 minutes, applying light pressure while rolling, until it is rolled into strips without being broken.

③ Pile-fermentation. There are two pile-fermentation methods: natural pile-fermentation and heated and moisture-retaining pile-fermentation.

Natural pile-fermentation is to pile the rolled leaves while hot, with a pile height of 1.5-2 m, and the pile surface tightly covered with mats to maintain temperature and humidity. After about 2-3 days, when hot air emerges from the surface of the tea pile and the temperature inside the pile rises to about 70°C, the pile should be turned once with a wooden fork, turning the surface pile leaves into the center of the pile and rebuilding the pile. The pile temperature must not exceed 80°C; otherwise, the pile leaves will be scorched and turn black, becoming unfit to drink. After turning the pile, after another 2-3 days, water droplets condensed from water vapor again appear on the surface of the pile, the pile temperature rises again to 60-65°C, and the leaf color turns yellow-brown or brown, which means the pile-fermentation is appropriate. Open the pile, pick out the coarse stems, and carry out the second drying.

Heated and moisture-retaining pile-fermentation is carried out in a specially built pile-fermentation room. The indoor temperature is maintained at 65-70°C, the relative humidity at 90-95%, with air circulation, and the moisture content of the semi-finished product is about 28%. If such conditions can be provided, the pile-fermentation process requires only 36-38 hours to meet the requirements. Not only is the time short, but the pile-fermentation quality is also good, and the total water extract can be increased by 2%, with excellent color, aroma, and taste.

④ Drying. After pile-fermentation, the moisture content of the tea material is above 30%. But the moisture content requirement for Zuozhuang tea is 12-14%. Therefore, the tea material after pile-fermentation must undergo drying treatment to meet the requirements, and this can also fix the quality and prevent deterioration.

Drying is carried out in two stages; the moisture content of the first dried leaves reaches 32-37%, and the moisture content of the dried leaves is 12-14%. Machine drying is generally used.