If you’re a tea lover, then you must know that tea is produced from the Camellia sinensis plant. But have you ever asked yourself how the tea producers develop different tea flavors? If you’re new to the tea processing industry, then this question is challenging especially in understanding the tea leaves processing to come up with the final product.
Tea processing refers to the process in which Camilla Sinensis tea leaves are converted into dried leaves for making brewed tea. The different categories of tea are produced through different manners and degree odd oxidation and drying processes.
Tea makers face numerous challenges during the processing of tea. From planting to harvesting and converting tea leaves to make tea, the process is both long and daunting.
Steps in Tea Processing
Tea harvesting is the most delicate stage in tea processing. It is done twice a year during early spring and early summer. Picking of tea leaves during autumn or winter is less common though it’s possible with a favorable climate.
When harvesting tea, pluckers harvest the leaves diligently to avoid damage. The majority of the tea leaves in the market are harvested by hand picking though some industries use mechanical pluckers. Manual harvesting is the most common method for many cultivators as it enables them to pick younger leaf shoots or those with high caffeine and antioxidants.
When picking, the farmers pull the flash with their arms, forearms or shoulders then grasp the tea shoot with their thumbs and forefingers and put them in a collecting bag. At times, the tea pickers use the middle finger with the thumbs and forefingers.
Manual harvesting, on the other hand, is the ideal method for large scale tea harvesting. It’s also the perfect method when the industry allows more room for error in terms of imperfection, damage to tea leaves or when quality is not a priority. Mechanical picking is common in teas that are processed through the CTC (crush, tear, curl) method. For the mechanical method, farmers wear a portable vacuum-like machine that cuts off the tea bushes and collects them in a storage container.
Withering is the first industrial process in the manufacture of tea. During the stage, tea markers prepare the tea leaves for processing. This is done by softening the tea leaves and expelling the excess water in the leaves. Harvested tea leaves contain between 74-83% of water which withering lowers down to around 70%.
After lowering water content in the tea leaves, the leaves become flaccid which makes it easier to twist and curl them. Withering is a very delicate process in tea processing which tea makers describe its effect as one that “makes or mars the tea”. Since water content in leaves vary with different seasons, a tea maker must set the appropriate withering levels to ensure the production of high-quality tea. To control the withering level, a tea maker usually adjusts the withering to a range of 3 hours- 18 hours.
Benefits of Proper Degree of Withering
- Facilitates more efficient and quicker oxidation due to improved enzyme activity
- It improves the color and aroma of tea due to the effect of amino acids
- It increases the desirability of the tea- however, it’s essential to avoid over or under withering tea is it affects its quality.
Also, chlorophyll is affected by the withering time. As withering time increases, chlorophyll content reduces. Chlorophyll is responsible for the earthy flavor and characteristic “green color” in green tea.
Withering times for different teas
- Yellow: 2-4 hours
- White: 12-36 hours
- Chinese green: 2-4 hours
- Japanese green: 30-60 mins
- Black: 4-18 hours
- Oolong: 30 mins- 2 hours
Note: Japanese tea makers usually skip the withering stage to preserve chlorophyll; however, they are dried several times to reduce chlorophyll content after killing off the tea enzymes. In rare cases, Japanese green teas may undergo withering for 30-60 mins.
Disruption is the third stage in the processing of tea. The western culture normally refers it as leaf maceration. During the process, tea leaves are bruised to enhance and promote oxidation. The tea leaves are passed through the rolling process to rupture their cell walls.
When the cell walls are ruptured, they come in contact with oxygen which allows them to mix with enzymes and chemical constituents. This process results in the production of important constituents that determine the tea flavor. These enzymes also trigger the oxidation process and also influence the tea taste profile.
Disruption is the most demanding step in tea manufacturing. Tea makers must thoroughly and evenly bruise the laves to product consistent tea batches. For dark teas, they must be thoroughly bruised and oxidized to produce their characteristic black color.
Many small scale producers now prefer machines to the traditional bruising processes. These machines are quite effective and don’t break the leaf which lowers its quality. When used during artisanal crafting, the machines increase the consistency of leaf quality and keeps the production process cleaner.
Processes in Leaf Maceration
1. Leaf Bruising
Leaf Bruising is common in oolong and at times, black teas. Leaf bruising creates tears in the leaf epidermis and re-instigate oxidation enzymes. During the process, tea manufacturers shake the leaves in a bamboo basket or using machinery to kneed and slightly tear the
During this stage, tea leaves are shaped to decent tea leaf shapes. Re-rolling lightly breaks the cell structure and instigate enzymes that promote the oxidation process. A few years ago, most tea makers were manually rolling leaves to shape but with the advent of technology, there are machines for the purpose.
- Crushing: Crushing is a disruption technique that involves cutting of tea leaves to smaller pieces by a machine to trigger the release of oxidative enzymes. Though the process is essential, it leads to exposure of a leaf’s essential oils that contain vitamins, antioxidants and other useful nutraceuticals present in tea. When these oils are exposed to oxygen they may experience oxidation damage that can neutralize the beneficial compounds.
- Crush, Tear, and Curl (CTC): CTC method was developed during the 1930s to reduce the amount of the required tea leaves for each teacup. The method is viewed as one that sacrifices the quality of tea for quantity. This method increases the exposed area of the tea which lowers the number of tea leaves necessary for brewing.
- Sweating and heaping: During the various stages or styles of tea processing, the leaves are normally heaped to piles to enhance their thermal and enzymatic activities. Thermal and enzymatic activities raise the heat in the leaves with the highest heat being at the center of the heap. Tea processors should observe the temperatures during this time and turn the leaves to distribute the sweat.
4. Oxidation/ Fermentation
Oxidation is a chemical reaction that involves oxygen. During tea processing oxidation leads to the browning of tea leaves, creation, and unlocking of new compounds. During tea leaves oxidation, leaves are left in a climate-controlled room where they turn darker. The process is accompanied by agitation, that is, the breaking down of chlorophyll in leaves to release tannins. The process is sometimes known as fermentation.
Related Article: Tea Fermentation vs Oxidation – Knowing the Difference
The tea producer determines the level of oxidation as well as the weather conditions. Oxidation leads to browning of the tea leaves which determines the different styles of tea. The preparation of green tea is entirely different from other types of tea and requires no oxidation hence its green color. Black tea, on the other hand, requires heavy oxidization that is responsible for its dark color.
The oxidation process occurs at a molecular level. There are two types of oxidation:
Passive oxidation refers to natural oxidation i.e. rusting of metals. The process is slower than active oxidation. After plucking off the tea, oxidative enzymes are activated leading to passive oxidation. During this stage, the leaves release aromatic compounds. The process then continues until the enzyme kill stage (when tea leaves are flushed with heat)
Controlled oxidation is where the conditions for oxidation have been manipulated through adjustment of conditions such as room temperature, humidity and breaking of the leaf epidermis. The degree of this oxidation is measured by several parameters.
To stop the oxidation process at a required level, the tea leaf is heated. When heat is applied to a leaf, it denatures its enzymes which stops further oxidation. In tea processing, a tea maker moderately heats the tea leaf to maintain its flavor while also removing unwanted scents in the leaf.
The fixation process applies to all tea types expect black tea as the drying process halts oxidation in the tea. Fixations are sometimes known as kill green; however, the process also protects the remaining green color in the tea leaves.
Also, depending on the method of heating, differences arise in the taste of tea. For instance, steamed Japanese green teas taste wildly than roasted Chinese green teas. Frying the leaves in a wok and roasting of tea leaves in a rotating drum creates different flavor profiles.
Also, the advancements in technology have led to the introduction of rolling drums for “baking” or “panning” the tea leaves. A rolling drum is more effective than the traditional wok.
6. Sweltering/ Yellowing
Yellowing is unique to yellow teas; it’s a process where warm and damp tea leaves are lightly heated in a closed container which turns the green leaves to yellow. The process results in a yellowish-green beverage due to changes in the leaf chlorophyll. After yellowing for 6-8 hours, at about 37°C, polyphenols and amino acids in the leaves go through chemical changes to produce a mellow taste and distinct tea briskness.
7. Rolling/ Shaping
The damp tea leaves are rolled to form wrinkled strips using a rolling machine which makes the tea to wrap around itself. The rolling action also causes some of the essential oils, juices, and saps inside the leaves to ooze out; this action enhances the taste of the tea. The strips of tea can then be modified to other shapes such as spirals, pellets, balls, cones and other shapes. During oolong tea preparation, the rolled strips of tea are usually rerolled to form spheres or half-spheres. This is made possible by placing the damp tea leaves in large cloth bags and knead them in a specific manner by hand or machine.
Drying is the second last stage in tea processing. The process is vital for “finishing” the tea for market sale. Drying is possible through a myriad of ways such as baking, sunning, panning or air drying. Baking is the most common method and great care must be observed to avoid overcooking the tea leaves. Drying is an integral process in many types of tea such as green tea as its responsible for its new flavor compounds.
9. Aging/ Curing
Though not necessary in most cases, the aging process improves the drinking potential of the tea. Some teas require additional curing and secondary fermentation to produce their best flavors. For instance, green tea has a bitter and harsh taste before curing. After aging, its taste changes to sweet and mellow. During this stage, tea makers produce flavored teas by spraying them with aromas and flavors.
Tea sorting is the final stage in tea processing. The process is vital especially in removing physical impurities such as seeds and stems. Though many small scale producers use hands to sort the tea, its best to use sorting equipment as it improves tea production efficiency. The equipment is popular in large tea processing plants and especially those that deal with black tea production. A color sorter is also popular during sorting as it classified final products based on their color and shape.
Tea processing is an integral process that must be done with due diligence and appropriate equipment. Production of high-quality brewed tea is not an easy process and requires the best-skilled manpower and equipment. Luckily, the improvement of technology across the agricultural sector has led to the manufacture of modern equipment that has led to an improvement in production efficiency in the tea sector.