Submitted to-:
(Depaertmaent of Food & Agricultural Engineering)
Submitted By-: B.Tech (Food Technology) 8TH Semester (2005-09 Batch) Mahatma Gandhi Chitrakoot Gramodaya University, Chitrakoot Satna (MP) 485331
Tea Introduction to Tea-: Tea is a natural beverage brewed from the leaves of an evergreen plant called Camellia sinensis. While it has become common place for people to refer to any hot beverage that is brewed from naturally occuring plants or plant extracts as "tea" technically, those herbal hot beverages should be called "teassanes", as the word "tea" is reserved for beverages brewed from leaves of Camellia sinensis .
Tea refers to the agricultural products of the leaves, leaf buds, and internodes of the Camellia sinensis plant, prepared and cured by various methods. "Tea" also refers to the aromatic beverage prepared from the cured leaves by combination with hot or boiling wate We know that tea is the most widely consumed beverage in the world, most consumed after water. Most people, who drink tea, prefer to go with a certain brand because of familiarity of taste, aroma, liquor etc. In order to maintain that kind of consistency, tea companies tend to blend teas from various sources until they arrive at their brand's trademark features. This consistency appeals to the masses, and allows manufacturers to produce the teas in thousands of kilograms for mass consumption.
Versatile Plant-: The camelia sinensis is a very versatile plant that can grow under almost any conditions. Thus, tea is grown around the world from the Indian Sub-continent in India, Nepal, and SriLanka, to China, Japan, Indonesia, Vietnam, to the African subcontinent in
Kenya, to Latin America in Argentina. As can be imagined, the quality of tea varies dramatically from region to region, with most of the variations originating in the variation in the climactic conditions of the regions where the tea is grown and not from the differences in the tea bush itself.
Difference in flavor of teas-: The largest difference in flavor of teas comes from the altitude at which the tea is grown and the type of soil the bush is grown in. High growth teas tend to be far superior to the lower growth regions with respect to the subtelities of flavor, color and fragrance. The flavor of the teas is also dependent upon the kind of leaves that have been plucked. The younger the leaf, the more flavorful the tea. A fine pluck often means that only the buds of the new growth have been plucked, where a coarse pluck means that more coarse, older leaves were plucked.
Types of Tea-: Once the tea leaf is plucked, it is processed in the factory to bring out the flavors in it. There are essentially two types of teas: Orthodox, and CTC. The Orthodox tea is the whole leaf tea that is generally popular in the west, but in India, CTC tea is wildly popular for the type of tea they make there, called Chai, involving boiling the tea over and over to extract the most out of it.
1. White tea Recently popular, white tea is produced when two leaves and a bud are picked just before sunrise to preserve the moisture in the leaf. This tea is characterized by a delicate flavor with very little color, however it is highly priced because a days picking produces only about 1 - 2 kgs. Although it is called white tea, the tea does have some light green color charactersitic of the newest buds originating on the bush. The buds are steamed to destroy the enzymes that would otherwise destroy the tea and dried either in the dryer or in the sun.
2. Green tea-: Green tea is produced by steaming the leaves to destroy the enzymes that might otherwise ferment the leaves. The leaves are then rolled either by hand or by mechanical rollers, to bring out the juices in the leaves that are responsible for its flavor. The rolled leaves are then fired to dry them. The entire process of rolling and firing is repeated several times until the leaves are completely dry. The process of producing green tea is very exacting because variation in the drying time can result in fermentation of the leaves which spoils its flavor.
3. Black Tea-: The most widely consumed beverage, black tea is a close cousin to the Oolong in that if the tea is fermented long enough, the leaves turn black, hence the term "black tea". The exact time of rolling is determined by the size of the leaf, with smaller leaf being rolled for shorter period than larger leaf. Rolling induces fermentation of the leaf, and when the leaf is judged to be appropriately fermented, the process is slowed by allowing the leaves to cool off on ventilated trays for 3 to 4 hours. Finally, the fermentation process is stopped by drying the teas under hot blowers, at which point the tea leaves turn from reddish hue to black. The teas are then passed through various sieves to grade them.
4. Oolong Teas-: Oolong teas are semi fermented teas that are partially fermented before drying to preserve the natural flavors. The process of producing Oolongs begins with picking of the two leaves and a bud, generally early in the morning. The leaves are then partially dried indoors to promote fermentation. When the leaves start turning red - at a stage, when 30% of the leaves are red, and the rest 70% are green, the leaves are rubbed repeatedly by hand or mechanically to generate flavor and aroma, and finally dried over charcoal. The final stage in production of Oolong teas is blending the teas to produce the characteristic flavor of the garden or the brand.
Manufacturing Process-: The black tea manufacturing process is quite an involved one, buy first, the tea has to be plucked. While in the industrialized country like Japan this activity is performed using a mechanical harvester, in India this is mostly done by hand. It is usually the ladies who are considered the better pickers. They tend to be vey deft at picking only the two leaves and a bud, and leave the more coarser leaf alone.
Once the leaf basket if full, the picker brings it to the central station where the basket is weighed and passed on to the factory floor. On the factory floor, the tea undergoes a withering process designed to remove as much moisture as possible from the tea, to prepare it for oxidation and drying. Usually, the tea leaves are spread out on a large tray of wire mesh, and hot air blowers are used to heat the leaf and drive the mositure out. At higher elevations, it is not unusual for the withering process to require 12-24 hours. At this point, the leaf has become limp and turned into a darker shade of green. The next step in the process is Rolling wherein the leaf is put into roller machines which twist and turn the leaf and break it, giving it the wirey shape characteristic of Darjeeling orthodox leaf. This process of rolling releases the enzymes from the leaf as the leaf breaks, exposing the juices to natural process of oxidation.
In the next stage, the Oxidation stage, the leaf is allowed to oxidise by exposing it to air in large trays. As the leaf oxidizes, it generates heat, and slowly changes in color from green to red to brown to eventually black.
Proper oxidation of the leaf is critical in the final flavor and color produced in the leaf. If the leaf is oxidised at too high a temperature, it would spoil the tea, and if it is oxidized at too low a temperature, the tea produced would be flavorless. Finally, the tea is ready for drying. Once again, the leaf is exposed to hot air from air blowers, which drive the remaining moisture out of the leaf. Once the leaf is dry, the tea is marked and tasted by an expert taster who describes the tea and issues the certificate of release. Often times, a blender blends various batches of tea to produce a characteristic flavor, however, most blending work is not done at the tea garden level. Rather, this happens at the blender and packers warehouse. This is where the manufacturing process generally ends, and the tea arrives into the market place.
Production of Tea In India-: Tea is a highly adaptable plant, a result of which is that tea is grown around the world. However, among the tea producing nations of the world India stands head and shoulders above any other India producing over 826 million kgs. Indian tea thus has over a quarter of the world market with a market share of about 28%.
Health Benefits of Tea-: Contrary to the concerns of health associated with Coffee, it has been scientifically scientifically established that tea offers several health benefits to the consumer. Most of the health benefits of the tea are associated with the antioxidant properties of polyphenols called "flavanoids". While much of the research on flavanoids has been done with Green Tea, Black tea too contains about the same amount of flavanoids as Green Tea. The major difference between Green Tea and Black tea is the fact that Green Tea has more simple flavanoids called cathechins cathechins as compared to Black Tea, which contains more complex flavanoids called theaflavins and thearubigins.
Antioxidative properties properties of tea-: The harmful effects of free radicals are quite well known. Free radicals, or unstable molecules of nitric oxide and oxygen are produced during the normal operation of cellular processes. These free radicals, unless removed, can cause immense damage to the DNA and other units of the cell. Under normal circumstances, the body is equipped to eliminate the free radicals by itself mainly through the presence of an enzyme called Super Oxide Dismutase. However, when exposed to harmful conditions such as exessive UV exposure, exposure to smoke, or pollution, the number of free radicals produced increases dramatically, which can be harmful to the body.
Three Cups A Day Keeps The Doctor Away-: Antioxidants, such as the flavanoids found in the tea, are known to scavenge the free radicals, metabolize lipid peroxides, and precipitate metal ions, there by preventing further damage to the critical cellular processes. Fruits and vegetables are a natural source of many antioxidants but tea is not too far behind. In a UK study it was found that 3 cups of tea contains the same amount of antioxidants as six apples.
In Summary-: In summary, Tea is a very potent source of antioxidative flavanoids such as Cathecins, Theaflavin, and Thearubin. Flavanoids have been demonstrated to have various health associated properties, in lab experiments and in some human experiments. Both Green and Black teas contain about the same amounts of these poly phenols, so you can get the same health benefits from either type of tea.
Storage & Self Life Of Tea -: Tea has a shelf life that varies with storage conditions and type of tea. Black tea has a longer shelf life than green tea. Some teas such as flower teas may go bad in a month. Tea stays freshest when stored in a dry, cool, dark place in an air-tight container. Black tea stored in a bag inside a sealed opaque canister may keep for two years. Green tea loses its freshness more quickly, usually in less than a year.
