Tea processing machinery by stage: withering to drying

Same leaf, different route

Green, black and white tea come from the same plant. What separates them is the order of the processing steps and how long the leaf is allowed to oxidise before heat stops it. For a buyer, that means a tea factory is a chain of tea-processing machinery chosen for one route, and the first line of any enquiry should name the tea you want to make, the daily fresh-leaf intake and the finished style.

In outline, green tea is spread, fixed with heat, rolled or shaped and dried. Black tea is withered, rolled to break the cells, fermented (oxidised) and then dried. White tea is the simplest: buds and young leaves are withered and dried with very little handling in between [3]. One naming trap is worth knowing. Several pale-leaf Chinese teas sold as "white", including Anji Bai and Zheng'an Bai, come from albino cultivars and are processed with spreading, fixation and drying, so in machinery terms they need a green-tea line [4].

Withering and spreading

Withering is a partial drying step that takes moisture out of the surface and the inside of the leaf and starts the chemical changes the later steps depend on; it also uses a large share of a factory's energy [5]. For orthodox black tea, the UPASI tea institute in South India describes about 16 to 18 hours in trough systems with ambient air, with heaters and fans used in wet weather, aiming for leaf at roughly 60 to 65 percent moisture [1]. White tea withers far longer, often 36 to 48 hours or more, in sun, indoors or in fan-ventilated tanks, until the leaf drops to about 20 to 30 percent moisture [3]. Green tea gets a shorter spreading step instead; in one Chinese trial the leaf was spread for 8 to 10 hours down to about 70 percent moisture before fixation [2].

On the machine side, a single-layer withering module or trough suits smaller batches, while a multi-layer circulating withering module saves floor space at higher intake. Hongming offers the HONGMING 6CWF/6CDF continuous withering line for black-tea projects, and its fresh-leaf tray loader spreads leaf evenly on trays. Ask each maker for spread area per kilogram of fresh leaf, air volume, heater power and how temperature and humidity are controlled.

Fixation: pan, drum, steam and hot air

Fixation (kill-green) heats the leaf quickly to stop enzyme activity. It defines green tea and is skipped in black and white tea. The heat source changes the cup. A 2023 study in Food Chemistry X compared methods on straight-shaped green tea: roller (drum) fixation at about 280 to 300 °C for two minutes is low cost, suits large-scale work and is the most common method in China, giving strong aroma but more bitterness; steam followed by hot air kept a stable green colour while the hot-air stage helped aroma, and the authors note the combination has spread quickly in industry [2].

Match the machine to the method. A continuous drum such as the Sunyoung 6CST-40 drum fixation machine is the workhorse for volume. The 6CZS-65 steam and hot-air module covers the steam route, the 6CSF hot-air fixation module is a hot-air option, and the 6CSFT infrared module adds a radiant choice. Hongwuhuan also builds hot-air drum fixation machines. Pan fixation and pan roasting belong to flat teas such as Longjing, where machines like the Hengfeng 6CCB-842ZD flat tea roaster and the Yinqiu 6CCB-781ZD fix and press the leaf in heated pans.

After fixation, a cooling and wind-selection module brings the leaf temperature down and blows out light fragments before rolling, which mirrors the one-hour cooling step used in the study above [2].

Rolling, clump breaking and shaping

In black tea, rolling twists and breaks the leaf so the juices meet air and oxidation begins; a roll-breaker then loosens compressed lumps, cools the leaf and sorts it by size so fermentation stays even [1]. In green tea, rolling builds the shape and helps the leaf release moisture evenly, usually with staged pressure from none to light to heavy and back [2].

Batch machines such as the Sunyoung 6CR tea rollers and the 6CRZ-55 automatic rolling module cover both teas, and clump breakers follow them on black-tea lines. For green tea, 6CLZ strip shapers form straight strips, and in the trial cited above the shaping step ran at 80 to 100 °C [2]. When comparing rollers, ask for drum diameter, kilograms of leaf per batch, the pressure programme and cycle time, then check that roller capacity matches what the fixation or withering stage delivers per hour.

Fermentation for black tea

Fermentation is controlled oxidation of the rolled leaf. UPASI gives working targets of leaf temperature below 30 °C, relative humidity above 90 percent and thin, even spreading, with the endpoint judged by colour and aroma rather than a fixed clock [1]. Equipment ranges from trays in a room to enclosed machines: Sunyoung lists 6CHFJ fermentation machines and a continuous fermentation module for linked lines, while Hongming builds a fresh-air fermentation room with variable temperature. Ask how humidity is generated, how fresh air is supplied and how evenly the leaf bed is turned or aerated.

Drying and finishing

Drying stops oxidation and sets keeping quality. Endless-chain dryers are common for black tea, with fluid-bed and hot-feed dryers as newer options [1]; green tea in the 2023 trial was dried at 80 °C until moisture fell below 6 percent [2]. Continuous belt units such as the 6CHB continuous dryers handle volume, and the automated Anji white tea line from Yuanfeng links shaping, air classification, conditioning and drying in one run. Dryers and fixation drums need a heat source, so specify fuel and burner type up front; Sunyoung lists heating furnaces for gas, electric and solid fuel. Downstream, packing machines such as the Haowei DZH-100A cartoning machine close the line.

Planning a line and comparing quotes

Start from fresh-leaf intake per hour or per shift, then size every stage to that number, counting the weight lost at each step so dryers and shapers are not oversized. Leave space for conveyors and elevators between stages, plus buffer trays where batch machines feed continuous ones.

Ask every maker for the same items: capacity in fresh leaf per hour at each stage, installed power and fuel use, control system and recipe storage, food-contact materials, layout drawing and spare parts list. With the route named and the figures lined up stage by stage, quotes from different factories can be compared on equal terms.

Source notes

[1] UPASI Tea Research Foundation — Orthodox (black tea manufacture) (n.d. (accessed 2026-11-04)) [2] Food Chemistry: X (Elsevier), via PubMed Central — Insights into the effects of fixation methods on the sensory quality of straight-shaped green tea and dynamic changes of key taste metabolites by widely targeted metabolomic analysis (Xue et al.) (2023) [3] Beverage Plant Research (Maximum Academic Press) — Flavonol glycosides in tea: the role of mitigating oxidative stress during the withering process (Prawira-Atmaja & Puangpraphant) (2025) [4] Frontiers in Nutrition — Widely targeted metabolomics and SPME-GC-MS analysis revealed the quality characteristics of non-volatile/volatile compounds in Zheng'an Bai tea (Liu et al.) (2024) [5] Agricultural Engineering International: CIGR Journal — Scientific and Technological Aspects of Tea Drying and Withering: A Review (Sharma & Dutta) (2019)