Week 6 Notes: Preparing for Red/Black Tea Workshop
· Linnaeus first classified as Thea sinensis
· Later named Camellia sinensis
· SE China
· Camellia Sinensis
1. Var. Sinensis, C. sinensis
2. Var. Assamica and C sinensis
3. Var. cambodiensis
Cultivated china type of tea
· Slow growing shrub with a number of stems arising from the ground and small hard leaves. Hardy and may grow in high latitudes where winters are cold and at high altitudes in the tropics.
· Grown under natural conditions, in a large tree with big, glossy, bullate leaves well adapted to tropical conditions.
· Most regions of the SE Asia the sinensis type has therefore been replaced by the assamica type and by hybrids for commercial purposes.
China vs Assam
· Productivity is lower in china type vs. assamica.
· Assam/attains heights varying from 10 to 20 m, while china tea seldom reaches 10 m.
· Under cultivation for commercial purposes the tea plant is trained as a low spreading bush and subjected to various treatments including plucking and pruning to maximize crop of young shoots.
· The normal harvest consists of regular plucking of young shoots from the plucking table at intervals of some 7-12 days. The number of tea bushes per ha ranges from about 7,000 to 15,000 and the economic life span of a commercial tea plant is about 50-60 years. (Depending on environmental conditions and cultivation methods.
· Assam tea
· Assam tea grown in principal cultivation areas (the tropics) thrives under a well-distributed rainfall of at least 1,500 per year.
· High humidity and even temperatures with a mean minimum not below 55 degrees F.
· The crop requires a deep permeable tolerant to lower temperatures and therefore suitable under subtropical conditions.
The principles of tea processing
· The freshly plucked young shoots of the tea bush, are withered by moisture evaporation during some 16-20 hours to prepare the leaf for further processing.
· The withering continues to a stage in which the material physically can be rolled without breaking up excessively and chemically has undergone certain changes and in which the concentrated juice can be wrung out by a twisting action.
· The rolling of the withered leaf the cell contents of the bruised material are mixed and aerated. Started by an enzyme taking up atmospheric oxygen the polyphenolic bodies in the leaf belonging to the catechin group are more or less oxidized.
· Subsequently yellow theaflavins and red and brown thearubigins are produced.
· After rolling the material is subjected to further fermentation by spreding it under adequate conditions of temperature and humidity and for such a period that the best quality of made tea is obtained.
· Apart form moisture removal and inactivation of the oxidizing enzyme, some of the unchanged Catechins are changed chemically then, while gums are dried through enzymatic action to a varnish contributing to the keeping quality of the made tea.
· Sugars are carmelized, resulting in the smell of burnt toast or caramel type of dried teas.
By: Kevin Gascoyne, Francois Marchand, Jasmin Desharnais and Humo Americi
Tea: History, Terroirs, Varieties
Black Tea overview and brief history
· Made from completely oxidized leaves.
· Found in south China
· Providences of Yunnan, Anhui (particularly Qimen) Fujiuan (particularly Zhenghe)
· Process to develop black tea was invented in the 18th century
· Usually more mature leaves are picked for the production of black teas except in the case of very high quality teas.
1. Withering: on the ground or on bamboo racks, lasts for 5-6 hours. They lose 60% of their moisture. The leaves need to be stirred often. Mechanical processing withering takes place in a controlled environment. The leaves are placed on sieves in brick containers that are usually heated by wood fires. This technique has given Chinese teas a smoky aroma. The containers allow air from the turbine to circulate below the leaves about 4 hours later the leaves are ready for the next stage.
2. Rolling: Leaves are rolled to break down the structure of the cells. Depending on the quality of tea desired, this is usually done by a machine that presses the leaves onto plates divided into strips.
3. Oxidation: The oxidation period can vary from 8-12 hours depending on the ambient conditions. The leaves are spread on the ground and covered with large wet cloths to stimulate the chemical reaction. The Temperature must be around 72 degrees F. (This technique takes longer than the method used for Indian black teas.) The Indian black teas are oxidized in milder conditions and a less astringent tea is obtained. This method also produces an earthy aroma and burnt, sweet taste.
4. Drying: Any residual moisture in the leaves is eliminated and the oxidation process is stabilized during the drying stage. Warm air can be blown onto the dry leaves or sometimes they’re transferred to another wood-heated machine.
5. Sorting and Sifting: Whether manually or mechanically sorted and sifted the leaves are put into different grades. This also eliminated dust, branches, and other residue.
6. Firing (optional): In certain cases firing can reduce the moisture content and helps standardize the batch.
Black Tea from Taiwan
· T-18 is a hybrid produced from a tea tree from Burma (Myanmar) called Ashamu and a wild tea tree from southern Taiwan.
· After 40 years of research and observation T-18 stuck out from similar hybrids because of its superior sensorial characteristics and it was launched onto the market in 1999.
· Can be found in the region around Sun Moon Lake (largest natural lake in Taiwan)
· Whole leaf black tea
· Minimal quantities are produced
1. Processing: withered for 16-22 hours, four periods of mechanical rolling, lasting 30 min
2. Oxidized for two hours at 77 degrees F and a level of humidity of approximately 95%
3. Two stages of drying will follow lasting 30 minutes each at a temp of 210
4. Lastly, it is sorted, usually mechanically. The finest batches will be sorted with tweezers to prevent hands from transferring undesirable aromas to the leaves.
The Chemistry of Red/Black Teas
· Polyphenols are essential components of tea leaves. In the fresh leaf they are colorless and acrid but during oxidation these enzymes are transformed into theaflavins and thearubigins. The two elements that give tea its color and astringency. Oxidation develops brown, red and black pigments and reduces the astringency.
**Example of the color related to a higher content of theaflavins and thearubigins. Usually associated with Red/Black Tea and Pu er.
History of processing black tea in India
· In order for the British to compete with low production cost of the Chinese (who had access to a cheap labor force)
· The British had to invent every stage of the processing. They needed to reduce costs by turning their tea plantations into industrial enterprises.
· Methods to process black tea started in the 17th century
· The British quickened the process by mechanizing the whole process. At the end of the 19th century they created the first industrial technique, the orthodox process.
· The mechanized process requires expertise and intuition and allows for greater control over the different variables that affect the chemistry of the leaves.
The orthodox method
· Developed by the British in NE India around 1860 and constantly improved upon since, it is one of the oldest mechanized methods of black-tea processing. It consists of five steps: withering, rolling, oxidation, dehydration, and sorting.
1. Withering: Withering reduces the water content of the leaves softening them and changing the waxy texture so they can then be rolled without breaking. The ambient humidity ventilation and temperature are constantly monitored to ensure successful withering. After 14 to 17th hours the moisture content of the leaves will have been reduced by 60-70%
2. Rolling: 10-20 minutes the piles of leaves are held in copper vats inside enormous machines. These machines roll the leaves under pressure until they form a compact mass. Next with the aid of a rolling machine, various levels of pressure are applied to the leaves following precise cycle until their cellular membranes are broken, releasing the oils they contain. As soon as these oils are exposed to the air the phenomenon of oxidation begins If the rolling is too intense the leaves will be discolored and dull. If too light the leaves will be dry gray and dusty and brew into a pale and tasteless liquid.
3. Oxidation: contact to oxygen the enzymes contained in the oils of the leaves trigger a chemical reaction called enzymatic oxidation. The leaves are spread out on trays made of stainless steel ceramic or glass in a humid environment, 68-86 degrees F.
4. Drying: Dehydration puts an end to the process of the oxidation. The leaves are placed either on either conveyors or on a series of revolving trays in a large machine that is heated to a temp of 248 degrees F. If the drying is incomplete the oxidation process will continue uncontrolled. If it is too intense the leaves will burn and acquire a smoky taste. The process lasts 20-30 minutes until the moisture content of the leaves is reduced to 2-6%
5. Sorting: After the drying stage the leaves are sorted using vibrating grids of varying sizes placed one on top of another separate the leaves into different grades. The largest leaves remain on the top grid while the crushed leaves (fanning) and dust fall to the ground. The intermediate leaves are caught by other grids. In Darjeeling, all teas, regardless of the quality are sorted in this way. The grade a tea is given is therefore an indication of size, not quality. Sorting is however an essential step and the size of the leaf requires a different infusion time and will have different characteristics.
· Stands for crushing, tearing, curling. It is an industrial method that was developed in India by Sir William Mckercher. In the 1930’s, borrowing ideas from existing machinery he perfected the system of industrial processing that would speed up the oxidation process and produce higher yields more quickly. The CTC has three steps
1. Brief withering, the leaves are then cut and crushed in metallic cylinders equipped with blades.
2. During this step they are torn apart by a machine called a Rotorvane.
3. The leaves are then sent to a ghoogi, a large barrel in which they are rolled into small beads.
· At first only used for coarser leaves, this method gained in popularity in the middle of the 20th century. With the invention of tea bags. It revolutionized the tea industry but also at the expense of quality. The majority of leaves used in the CTC method are of inferior picking quality.
· Creates high volume and uniform quality.
Grades of Black Tea
· Three major systems of grading black tea. The grades refer to the state of the leaves (whole, broken, or crushed) then to their taste quality.
· Whole leaves will result in a more complex and aromatic infusion where as broken leaves create a darker liquid with a simpler flavor profile.
· Grading system used in Darjeeling/whole leaf tea.
· The most important aspect is the number of buds (pekoes) the most buds a tea contains, the more letters there are in its appellation.
1. SFTGFOP: Special Finest Tippy Golden Flowery Orange Pekoe
2. FTGFOP: Finest Tippy Golden Flowery Orange Pekoe
3. GFOP: Golden Flowery Orange Pekoe
4. FOP: Flowery Orange Pekoe
5. OP: Orange Pekoe
· Tippy: refers to the abundance of flowering buds
· Golden: the tips that turn golden after oxidation
· Flowery: slightly floral aroma released by the buds.
· Orange: purely historic reference to the Dutch royal family of Holland-Nassu, who were among the first to import tea into Europe.
· Pekoe: comes from pak-ho meaning “white down” Also used to describe the hair of newborn babies. Here it refers to the final leaf on a branch (final bud) which is covered in a fine white down.
· The numeral 1: Sometimes appears at the end of the grade of certain batches, the letter S will be added if the batch is exceptional.
Steeping Black teas
1. Darjeeling (all gardens, regardless of picking season) Assam, Nilgiri, Kenya, Jin Zhen, Qimen, Zhenghe Hong Gong Fu, Cylan
2. Crushed broken or whole, small or medium length leaves, varying from brown to black, sometimes with golden or silver tips (buds) some first-harvest Darjeeling tease have green or brownish green leaves
3. ½ oz (2.5 grams) tea to 1 cup of water
4. 203 F
5. 3-4 minutes steeping
Therapeutic Effects of Tea
Beneficial Health Effect of Black Tea: Increasing Evidence
Beneficial Health Effect of Black Tea: Increasing Evidence
· Tea Catechins and its metabolites act as bio antioxidants
· Tea polyphenols are strong scavengers against superoxide, hydrogen peroxide, hydroxyl radicals, and nitric oxide produced by various chemicals.
· Black tea has been identified to act as a powerful chemopreventor of reactive oxygen and nitrogen species.
· Black tea exhibits protective effects against oxidative damage in human red blood cells.
· Treatment of ECGC to human skin inhabited ultraviolet radiation induced oxidative stress. EGCG also exhibited protective effect against oxidative damage to cellular DNA
· Black and Green tea inhibits lipid perozidative damage in rat liver and kidney
· Black tea ingestion reflected a significant increase of human plasma antioxidant capacity
· Offers protection against oxidative damage to red blood cells
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