KERALA AGRICULTURAL UNIVERSITY

KELAPPAJI COLLEGE OF AGRICULTURAL ENGINEERING & TECHNOLOGY

SEMINAR REPORT On

TEA

AJNA ALAVUDEEN

2011-06-001

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CONTENTS

Abstract.......................................................................................... 3

Introduction.................................................................................... 4

Tea.................................................................................................. 5

Types of tea..................................................................................... 7

Instant tea........................................................................................ 9

Components of tea........................................................................... 9

Equipments used in tea processing.................................................... 10

Common grades of tea....................................................................... 12

By product utilisation of tea.............................................................. 12

Health benefits of tea......................................................................... 14

Case studies....................................................................................... 15

References......................................................................................... 16

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ABSTRACT

Tea is one of the true stimulants and satisfying the palate demands of human beings for centuries. Teas can generally be divided into categories based on how they are processed. There are at least six different types of tea: white, yellow, green, oolong (or wulong), black (called red tea in China), and post-fermented tea. Tea contains a large number of possibly bioactive chemicals, including flavonoids; amino acids, vitamins, caffeine and several polysaccharides, and a variety of health effects have been proposed and investigated. Tea has wide applications so it processed in many ways so as to get different products.

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INTRODUCTION Second to water, Tea is the most commonly consumed beverage in the world. People drink more tea than coffee, soft drinks, dairy products, and alcohol combined. India is the world's largest tea grower and produces some of the best teas on the planet. Ineeka's family-owned organic tea estates are located in two of India's best tea producing regions - Darjeeling and Assam - both prized for their unique teas. The importance of tea in the world economy cannot be overstated. It is one of the most valuable primary products in world trade. It is one of the true stimulants and has been satisfying the palate demands of human beings for centuries and also the oldest known and is now the most popular beverage.

The tea plant and tea drinking habits were exclusively Chinese initially, but there tea drinking has undergone changes to suit the styles and requirements of countries of its later adoption. Different techniques are used for the processing coupled with consumer acceptance have led to the development of a wide variety of tea which appearance, colour, briskness, aroma etc to satisfy every consumer taste within and outside the country of origin.

The history of tea in India spans more than 160 years. The rapid expansion of cultivation in Assam followed by the establishment of plantations in Darjeeling, Teerai and the Dooars regions of northern Bengal, and the Nilgiris and other regions of southern India. The global production of tea is to be around 2.78 billion kg; about 3 billion cups of tea are consumed daily world wide.India, Srilanka and China together account for about 60% of the global production of tea.

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TEA

Scientific name :Camellia sinensis.

Family : Camelliaceae.

Camellia Sinensis, an ever green shrub that grow to height of 30 feet, but is usually clipped to a height of2-5 feet in cultivation for easy plucking purposes. Harvest of its leaves is by hand with special shears, or by machines. It is cultivated as a plantation crop, like acidic soil and a warm climate with at least 50 inches of rain per annum.tea from individual plantations has developed its own character and taste, depending on the direction of the growing slopes and weather conditions at the time of plucking leaf and manufacture from green leaf to black tea. Tea breaks down into three basic types: black green and oolong.

Tea Processing

It is a method in which the leaves and flushes from camellia sinensis are transferred in to the dried leaves for brewing tea. The types of tea are distinguished by the processing they undergo. In its most general form, tea processing involves oxidising the leaves, stopping the oxidation, forming the tea and drying it. Of these steps, the degree of oxidation plays a significant role of determining the final flavour of the tea, with curing and leaf breakage contributing to flavour by a lesser amount. Although each type of tea has different taste, smell and visual appearance, tea processing for all tea types consists of a very similar set of methods with only minor variations:

1. Picking

Picking is done by hand when a higher quality tea is needed. Hand picking is done by pulling the flush with a snap of the wrist and does not involve twisting or pinching the flush, since doing the latter reduces the quality of the leaves tea flushes and leaves can also be picked by machine, though there will be more broken leaves and partial flushes.

2. Withering

Withering is used to remove excess water from the leaves and allows a very slight amount of oxidation. The leaves can be either put under the sun or left in a cool breezy room to pull moisture out from the leaves.

3. Rolling/bruising

In order to promote and quicken oxidation, the leaves may be may be bruised by tumbling by baskets or by being kneaded or by being kneaded or rolled over by heavy wheels. This also releases some of the leaf juices, which may aid in oxidation and change the taste profile of the tea.

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4. Fermentation

Fermentation is the most important stage in the manufacture tea. For this the leaves are left on their own climate controlled room where they turn progressively darker. In this process the chlorophyll in the leaves is enzymatically broken down, and its tannins are released or transformed. This process is termed to as fermentation. The tea producer may choose when the oxidation should be stopped, which depends on the desire qualities in the final tea as well as the weather conditions. For light oolong teas this may be anywhere from 5-40% oxidation, in darker oolong teas 60-70% and in black teas 100%. The mechanical aspect involves spreading out of the leaves macerated by rolling a layer 5-8 cms thick, for 45 minutes to 3 hours, depending on the quality of the leaves. Fermenting machines make the process continuous, that is, every unit of macerated leaf has to be spread out for individual treatment.

5. Fixation

This is done to stop the leaf oxidation at a oxidation at a desired level. This is followed by moderatively heating the tea leaves, thus deactivating their oxidative enzymes, without destroying the flavour of the tea.

6. Drying

After fermentation the tea is dried by passing through a drier .the objective of drying is to a) arrest fermentation b) remove moisture and produce teas with good qualities. The mass of leaf is exposed to hot air when it passes through a chamber is maintained at temperatures between 100-130C centigrade as its base range. It takes 15 minutes to half an hour to dry the leaf, when the enzymes are fully inactivated. After completion of the drying process the tea becomes fully black in colour.

7. Packaging

Tea is a markedly hygrospic material and while cooling and sorting it absorbs moisture. Before packing tea the accumated series of daily batches of each grade are bulked and mixed to obtain the highest possible degree of unity. Before packing tea is passed under powerful magnets to prevent possible pieces of iron mixing with the tea. Packing is the process of preserving the product using the cheapest but most appropriate material taking in to account the product properties.

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Types of tea

1. Green tea

Green tea is made from the leaves from Camellia sinensis that have undergone minimal oxidation during processing. . Green tea has become the raw material for extracts used in various beverages, health foods, dietary supplements, and cosmetic items. Many varieties of green tea have been created in the countries where it is grown. These varieties can differ substantially due to variable growing conditions, horticulture, production processing, and harvesting time. The main constituent of green tea leaves belong to the polyphenol group accounting for 25-35% on a dry basis.

Processing of green tea

Plucking

Withering

Steaming (for to inactivate the enzyme)

Rolling

Drying (100°-130°C)

2. Oolong tea

The processing of oolong tea requires only a partial oxidation of the leaves. After the leaves are plucked, they are laid out to wither for about 8 to 24 hours. Then the leaves are tossed in baskets in order to bruise the edges of the leaves. This bruising only causes the leaves to partially oxidize because only a portion of the enzymes are exposed to air. The taste of the tea is very rich. It can be sweet and fruity, or woody and thick, or green and fresh, all depends on the horticulture and style of production. Here only 50% fermentation is done.

Processing of oolong tea

Picking

Withering

Partial fermentation

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Partially dried

Rubbed

Storing/blending

3. Black tea

Black tea is a type of tea that is more oxidized than oolong, green and white teas. Black tea is generally stronger in flavour than the less oxidized teas. Black tea retains its flavour for several years. Here 100% fermentation is done.

Processing of black tea

Plucking

Withering

Rolling

Fermentation (100%)

Drying

Storage

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INSTANT TEA

Instant teas are produced from black tea by extracting the liquor from processed leaves, tea wastes, or undried fermented leaves, concentrating the extract under low pressure, and drying the concentrate to a powder by freeze-drying, spray-drying, or vacuum-drying. Low temperature used to minimize loss of flavour and aroma.

Processing of instant tea

Extraction

Decreaming

Aroma stripping

Concentration

Drying

Components of tea

1. Tannin

Tannins are a class of compounds in tea, especially black tea, which tend to have a bitter flavour and astringent properties. Teas high in tannins can be described as tannic. Tannins are naturally occurring and common, and are an important component of red wine. They are also responsible for the dark colour in some streams, as they are found in leaves and wood, and are released as organic matter breaks down.

2. Phenolic compound

The phenolic content in tea refers to the phenols and polyphenols, natural plant compounds which are found in tea. These chemical compounds affect the flavour and mouth feel and are speculated to provide potential health benefits.

3. Amino acids

Aspartic, glutamic, serine, glutamine, tyrosine, valine, phenylalanine, leucine, isoleucine and thiamine were found to be the principal amino acids present in tea leaf.Theanine alone contributed around 60% of total amino acid content. The amino acid plays an important role in the development of tea aroma during the processing of black tea.

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4. Caffeine

Caffeine is a purine derivative, which is 1, 3, 7-tri-methl xanthine.it has stimulating property and removes mental fatigue. The contribution of caffeine to the infusion is the briskness and creamy property resulting from the complex formed by caffeine with polypenols.

5. Carotenoids

The four major carotenoids,β-carotene,lutein,violaxanthine and neoxanthine .all these carotids were found to decrease appreciably during black tea manufacture.

6. Carbohydrates

The free sugars found in tea shoot are glucose, fructose, sucrose, raffinose and stachyose.

Equipments used in tea processing

1. CTC machine

Crush, Tear, and Curl (also Cut, Twist, Curl) is a method of processing black tea, Instead of the leaves being rolled as a final stage, they are passed through a series of cylindrical rollers with hundreds of small sharps “teeth” that crush, tear, and curl the tea.CTC was invented by William McKercher .CTC teas generally produce a rich red-brown colour when they are boiled by the Indian method. The drawback of the CTC method is that it tends by its nature, and unfortunately by adulteration, to homogenize all black tea flavours. In the process of crushing, tearing and pelletizing the tea leaves, large pressures and stresses occur which break down the cells, releasing large amounts of the phytins that normally oxidize to produce black tea’s mahogany colour. Since, regardless of origin, CTC teas in their dry form are generically “tea-like” in aroma, very similar in pelletized form, it is very easy to adulterate a more expensive CTC-type tea with inexpensive and generally mild lowland teas of the same process. Whole and broken leaf teas by contrast are quite varied in appearance, making adulteration more difficult.

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Fig: CTC machine.

2. Orthodox machine

The term orthodox is used by the tea industry to designate methods that adhere to traditional production guidelines. Orthodox processing calls for a wither of 18-24 hours, two to six rolling of one half-hour each, and a fermentation of 3-4 hours. There are also specifications for firing and drying.

Fig: orthodox machine.

Primary objectives are;

1. To repture the cell walls and exposes their contents.

2. To bring the contents of tea leaf cells in contact of air to start the process of oxidation

3. To break the larger twisted leaf in to smaller particles

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Common grades of tea

All tea is graded according to leaf size. One of the most common terms is ‘Orange Pekoe’, and is often mistaken for a type of tea. In actual fact it is a term that denotes a particular size of Black Leaf Tea. Grading is not related to its quality, that’s down to the climate, location and the type of processing. It is the leaf size that plays an important role in influencing the overall essence of a cup.

White Tea, Green Tea and Oolong Tea are generally not graded like most Black Teas. Here are the most common grades for black tea leaves.

F.O.P. Flowery Orange Pekoe - Refers to high quality whole leaf tea made from the first two leaves and bud of the shoot. India produces large amounts of this grade.

G.F.O.P. Golden Flowery Orange Pekoe - The golden refers to the colourful tips at the end of the top bud.

T.G.F.O.P. Tippy Golden Flowery Orange Pekoe - FOP with larger amount of tips

F.T.G.F.O.P Finest Tippy Golden Flowery Orange Pekoe - An even higher quality with more tips than FOP

O.P. Orange Pekoe: Refers to a high quality thin, wiry leaf rolled more tightly than F.O.P. Picked later in the year than F.O.P.

S. Souchong - A twisted leaf picked from the bottom of the tea bush. China produces this grade used in their Smokey teas.

By products utilisation of tea

1. Clean carpets

2. Clean antique rugs:

3. Shine wood floors: The tannins in black tea can help shine and colour hardwood flooring. Follow your regular floor cleaning routine by carefully rubbing some brewed tea into the floor (don’t use too much water on hardwood flooring) and letting it air dry.

 4. Polish furniture: Brewed tea also can help clean and shine wood furniture. Dip a soft cloth in a small amount of tea, and use it to wipe down the tables, chairs and more.

5. Clean mirrors and windows: Tea can remove stubborn, greasy fingerprints from glass, and make it sparkle. Simply rub a damp teabag on the glass or fill a spray bottle with brewed tea.

6. Clean toilet stains: Rumour has it that used tea bags can magically remove stubborn stains in the bottom of the toilet bowl. Just leave them in the toilet for several hours, then flush the toilet and brush the bowl.

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7. Get rid of fishy smells: Rinse your hands with tea after eating or preparing fish (or other stinky foods) to eliminate odours.

8. De-stink fridges: Instead of baking soda (or maybe in addition), try used tea bags in the fridge to absorb odours.

12. Clean the fireplace: Sprinkling wet tealeaves on fireplace ashes while scooping them out may help reduce blowing dust.

 14. Make a car air freshener: Likewise, you can freshen up the car without a chemical-laden commercial air freshener. Put lavender tea or other soothing herbal tea in a bag under the seat to fight odors. 

15. Soothe sunburn: Wet teabags can soothe sunburns and other minor burns. For full-body sunburn, soak in a tea bath.

 16. Soothe tired eyes: Warm, wet teabags can reduce puffiness and soothe pain around tired eyes — and teabags on your eyes look a little less ridiculous than cucumber slices.

 18. Soothe razor burn: A wet tea bag can also reduce and soothe razor burn.

 19. Drain boils: Cover a boil with wet tea bag overnight, and it should drain painlessly.

21. Dry poison ivy rash Dry a weepy poison ivy rash with strongly brewed tea. Simply dip a

Cotton ball into the tea, dab it on the affected area, and let it air-dry. Repeat as needed.

22. Save a broken fingernail: To salvage a partially broken fingernail, use a piece of mesh tea bag to create a splint of sorts between the nail and the broken piece. Coat in nail polish.

 23. Make soap: Tea is a useful addition when making glycerine soap. The texture and scent can help make the soap smell and cleanse better.

24. Help recover from injections: A wet teabag on an injection site can be soothing, for babies or adults.  

 25. Soothe bleeding gums: For an older child who loses a tooth, try putting a cold, wet teabag in the mouth where the tooth was lost. It can reduce bleeding and soothe pain.

 26. Make mouthwash: Similarly, toothaches and other mouth pain can be soothed with a rinse of antiseptic peppermint tea mixed with a little salt.

27. Shine dry hair: Brewed tea makes a good conditioner for dry hair. Rinse with (unsweetened) tea and leave to dry for a while, and then rinse again with water.

 28. Dye hair: Brewed tea also is a good natural hair dye. Mix rosemary and sage into dark black tea and let the mixture stand overnight. Strain the mix and thoroughly work it into your hair. Repeat as needed for the desired colour.

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 29. Improve skin: To protect and beautify skin, try bathing in green tea. Another widely recommended skin booster is chamomile tea in a facial steamer.

 30. Cure acne: Some acne sufferers swear by washing their faces with green tea to cure or reduce their acne.

 33. Improve breath: Gargling with strong tea can help reduce halitosis.

35. Cure the common cold: The same Chinese traditionalists also swear by tea as a time-tested remedy for many cold symptoms. Of course, others maintain that a cold will last seven days with tea treatment, or one week without.

37. Tenderize meat: Marinate tough meat in black tea to make it more tender.

38. Smoke it: Add tea to a smoker to make tea-infused cheeses and meats.

39. Boil eggs: The Chinese also like to add tea leaves to the water after boiled eggs are cooked. This adds some flavour and colour to the boiled eggs.

Health benefits of tea

Tea contains a large number of possibly bioactive chemicals, including flavonoids; amino acids, vitamins, caffeine and several polysaccharides, and a variety of health effects have been proposed and investigated.

1. Green and black tea may protect against cancer.

2. The catechins found in green tea are thought to be more effective in preventing certain obesity-related cancers such as liver and colorectal cancer.

3. Green and black teas may protect against cardiovascular disease.

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CASE STUDIES

Case study: 1 Degradation pattern of gibberellic acid during the whole process of tea production.

By Hongping Chen; food chemistry; volume138, issue2-3; 1-july-2013, pages 976-981

The residues of gibberllic acid in tea shoots made tea, and tea infusion were determined by ultra performance liquid chromatography tandem mass to study the degradation pattern during tea planting, processing and brewing. The dissipation rate of gibberllic acid was described using first order kinetics. Its half life ranged from 1.67 to 2.01 days in tea processing had equally important functions.Gibberllicacid residues in product intermediates and made tea. Except for water content, little gibberllicacid residue difference was found in tea shoots and made tea.Gibberllicacid dissipated rapidly in baking stage during processing. The transfer coefficient of gibberllicacid residues made from infusion was from 26.23%-54.55%.gibberllicacid extraction efficiency varied from different infusion times and concentrations of gibberllic acid in made tea. This research revealed that gibberllicacid may be safe when applied in tea gardens at suitable doses and picking intervals

Case study: 2 Lipid occurrence, distribution and degradation to flavour volatiles during tea processingBy Ramaswamy Ravichandran; food chemistry, volume 68, issue1 january2000; pages7-13

The contents of neutral lipid, glycolipid and phospholipids and their fatty acid composition in three cultivars (clones) and processed leaves at different stages of black tea manufacture were measured. Glycolipids account for nearly 50% of the total lipids and are rich in linolenic acid. Phospholipids were present in the least amount (15%) and had a high proportion of oleic, linoleic and palmitic acids. Neutral lipids were found in moderate amounts (35%) and had a high content of lauric, myristic, palmitic, stearic, oleic and linoleic acids. Well-marked clonal variations in fatty acid composition of the lipid fractions were registered. With the maturation of the tea shoot, the lipid content increased. Considerable losses of lipids/fatty acids were observed in the withering process and again in the firing process. The other stages of processing (rolling and fermentation) registered only a minor change in lipid/fatty acid contents. Wide variation in lipid and flavour content was observed with season and a relation was evolved between them. The reason for the superior flavour of orthodox teas over CTC teas is explained on the basis of their lipid degradation. The changes in lipid content/fatty acids were related to the volatiles produced.

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REFERENCES

1. K.C.Willson.1999.Crop production science in horticulture.CABI publishing, UK, 231p.2. Hongping Chen.2013.Degradation pattern of gibberellic acid during the whole process of tea production. Food chemistry .138: 976-981.3. Ramaswamy Ravichandran.2000. Lipid occurrence, distribution and degradation to flavour volatiles during tea processing. Food chemistry.68:7-13.4. Dr.Balasubramaniam.1995.Tea processing. Academic press, Newyork.

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