|Infobox on Tea
|Example of Tea
|This table shows only a selection of the most important countries of origin and should not be thought of as exhaustive.
|Stowage factor (in m3/t)
|Humidity / moisture
|Water content 4-6% (black tea), RH 60%
|1% essential oils
|If the product is at "shipping dryness", i.e. if there is no risk of degradation by mold etc. due to water content, ventilation is not required. If this is not the case, then 10 air changes/hour should be implemented
|Tea is extremely sensitive to foreign odors, contamination, moist, mechanical stresses and insect infestation.
Camellia sinensis is an evergreen plant that grows mainly in tropical and sub-tropical climates.
Tea plants are propagated from seed or by cutting; it takes approximately 4 to 12 years for a tea plant to bear seed, and about 3 years before a new plant is ready for harvesting. In addition to warm(er) zone, tea plants require at least 127 cm. (50 inches) of rainfall a year and prefer acidic soils. Many high-quality tea plants are cultivated at elevations of up to 1.500 metres: at these heights, the plants grow more slowly and acquire a better flavour.
Only the top 1-2 inches of the mature plant are picked. These buds and leaves are called flushes. A plant will grow a new flush every seven to fifteen days during the growing season, and leaves that are slow in development always produce better flavored teas.
A tea plant will grow into a tree of up to 16 metres if left undisturbed, but cultivated plants are pruned to waist height for ease of plucking.
Two principal varieties are used: the China plant (C. sinensis sinensis), used for most Chinese, Formosan and Japanese teas (but not Pu-erh); and the clonal Assam tea plant (C. sinensis assamica), used in most Indian and other teas (but not Darjeeling). Within these botanical varieties, there are many strains and modern Indian clonal varieties. Leaf size is the chief criterion for the classification of tea plants, with three primary classifications being: Assam type, characterized by the largest leaves; China type, characterized by the smallest leaves; and Cambod, characterized by leaves of intermediate size. The smaller the leaf, the more expensive the tea.
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, black, and post-fermented teas of which the most commonly found on the market are white, green, oolong, and black. Some varieties, such as traditional oolong tea and Pu-erh tea, a post-fermented tea, can be used medicinally.
After picking, the leaves of Camellia sinensis soon begin to wilt and oxidize, unless they are immediately dried. The leaves turn progressively darker as their chlorophyll breaks down and tannins are released. This enzymatic oxidation process, known as fermentation in the tea industry, is caused by the plant's intracellular enzymes and causes the tea to darken. In tea processing, the darkening is stopped at a predetermined stage by heating, which deactivates the enzymes responsible. In the production of black teas, the halting of oxidization by heating is carried out simultaneously with drying.
Without careful moisture and temperature control during manufacture and packaging, the tea may become unfit for consumption, due to the growth of undesired molds and bacteria. At minimum it may alter the taste and make it undesirable.
Tea is traditionally classified based on the techniques with which it is produced and processed:
|Wilted and unoxidized
|Unwilted and unoxidized, but allowed to yellow
|Unwilted and unoxidized
|Wilted, bruised and partially oxidized
|Wilted, sometimes crushed and fully oxidized
|Post fermented tea
|Green tea that has been allowed to ferment/compost
Although single estate teas are available, almost all teas in bags and most other teas sold in the West are blends. Blending may occur in the tea-planting area (as in the case of Assam), or teas from many areas may be blended. The aim of blending is to obtain better taste, higher price, or both, as a more expensive, better-tasting tea may cover the inferior taste of cheaper varieties.
Some teas are not pure varieties, but have been enhanced through additives or special processing. Tea is highly receptive to inclusion of various aromas; this may cause problems in processing, transportation, and storage, but also allows for the design of an almost endless range of scented and flavored variants, such as bergamot (Earl Grey), vanilla, caramel, and many others.
Tea contains catechins, a type of antioxidant. In a freshly picked tea leaf, catechins can compose up to 30% of the dry weight. Catechins are highest in concentration in white and green teas, while black tea has substantially fewer due to its oxidative preparation. Tea also contains L-theanine, and the stimulant caffeine at about 3% of its dry weight, translating to between 30 mg and 90 mg per 8 oz (250 ml) cup depending on type, brand and brewing method.
Tea also contains small amounts of theobromine and theophylline. Due to modern day environmental pollution fluoride and aluminium have also been found to occur in tea, with certain types of brick tea made from old leaves and stems having the highest levels. This occurs due to the tea plant's high sensitivity to and absorption of environmental pollutants.
Although tea contains various types of polyphenols and tannin, tea does not contain tannic acid. Tannic acid is not an appropriate standard for any type of tannin analysis because of its poorly defined composition.
Tea leaves are used to make an infused beverage which is classed as a semiluxury item.
A distinction is drawn between the China tea plant (e.g. from China, Japan and Taiwan) and the Assam tea plant (e.g.. from India, Sri Lanka, Indonesia and Vietnam), each variety yielding both leafy and broken grades of tea. Teas are also classified and graded depending upon the size of the tea leaves. The youngest, small top leaves (= pekoe tips) provide the most valuable teas, while the older, large bottom leaves provide less valuable grades.
Grades of tea are classified by:
- Country of origin
- Leaf size/shape
|Flowery orange pekoe
|Thin, wiry, often with a light covering of silky hairs
|Slightly twisted, often with white to golden yellow tips
|Flowery broken orange pokoe
|The leaf particles and fragments obtained during processing
|Finely divided tea dust
The product may be shipped as soon as 3 - 4 weeks after harvest, but 1.5 - 2.5 months may elapse before shipping. The tea shipped at the beginning of the season is the most valuable. Shipping tea later after harvest than this may result in quality degradation during transport, which may particularly affect the light southern Indian tea. Otherwise, tea has a long storage life of 18 months or more provided that proper transport and storage conditions are maintained. However, this does not apply to aromatized teas.
The water content of black tea must not fall below 2%, as the product otherwise becomes hay-like and its Essential Oils readily volatilize, while on the other hand, it must not exceed 9% as it then has a tendency to grow mold and become musty. The wood of the chest should have a water content of 10 to at most 12%, corresponding to an equilibrium moisture content of 60 - 70%.
Claims for damages must be thoroughly investigated and an answer provided to the following questions:
What route did the consignment follow and in which season?
Where is the odor impaired in the chests: only at the edges or in the middle?
How were the chests transported:
- Conventional loading
- Container shipment
- Type of container
- Position of the container on the ship
Have tea tasters been involved in the claim for damages?
Were analyses carried out by a food chemist?
More particulars on tea
Tea can be packed in one of the following ways:
- Plywood chests lined with Aluminium Foil
- Polypropylene or jute sacks lined with polyethylene
- Multiwall paper sacks lined with aluminium foil
Tea Associations recommend that tea is shipped in either plywood chests or multiwall paper sacks. Multiwall paper sacks are always shipped in containers, whilst a few chests are still shipped break bulk.
Water Damage, Fresh or Salt
When contaminated with water, the packages become stained or the top layer of the plywood becomes corrugated. With damage by salt water, a whitish deposit is sometimes left on the wood. If no salt deposit is in evidence, it becomes necessary, in order to distinguish between salt and fresh water damage, either to smell or to submit the stained portions to chemical tests. Although tea packages are lined, the contents can be damaged by water. When this occurs the tea will be damp and appear mouldy, possibly having a musty or brackish smell, and if the package has dried out the tea may be caked. To recover the sound portion, remove with care the lumps or pieces of caked tea, taking care not to mix the mouldy parts. Abandon that which is caked, dry or pasty in the angles and at the bottom. The tea should then run easily and can be recovered, although the quality of the salved tea may have deteriorated.
Tea that is carried in wagons that are not watertight may be damaged due to water accumulating on the floor of the truck and seeping into the packages. Insufficient firing in the factory on the estate may result in the teas turning out at destination in a spongy and possibly mouldy condition resulting probably in a heavy claim. This condition can be rectified by having the tea re-fired.
Damage of this nature is brought about by condensation forming on the metalwork of the hold and dripping on to the packages, and, as in the case of water damage, packages become stained. Unlike rain or sea water damage, the packages become extremely dirty, and on landing re-packing into new chests may be necessary, and the tea may be damaged.
Fire or Smoke
When tea has been in the proximity of fire, the packages may be scorched as well as perhaps suffering water damage by the use of preventative action against the fire. There may be occasions when the contents of the packages suffer smoke damage while the chests themselves remain clean. When tea is found to be tainted by smoke, difficulty may arise in deciding whether the tea was affected in course of production or during transportation. In such instances it would be advisable for inquiries to be made of the shippers to ascertain whether or not the tea had been reported smoke-tainted prior to shipment. It might on occasions be necessary to obtain an expert tea-taster’s advice for the purpose of ascertaining whether or not the tea is smoke-tainted.
Odours of Taint
Damage of this nature is usually caused by bad storage prior to delivery. Tea is very readily affected by contact with odorous goods and although it may be possible to disperse the taint by airing the affected tea, this can only be done to a limited extent. Very often it is not practicable to do so owing to the length of time and the amount of accommodation necessary to air the teas. Usually foreign odours or taint are picked up in shipment sheds at ports of shipment or in ships or from previous cargoes in containers, particularly from fruits and essential oils. As in the case of smoke damage it might on occasions be necessary to obtain an expert tea-taster’s advice for the purpose of ascertaining whether or not the tea is tainted. By examining the chests and the tea-taster’s report on the tea, it might be possible to tell where the taint has been picked up. It may be possible for tea damaged by taint to be sold for blending with cheap brands.
Loss of Weight
Normally tea properly manufactured should gain in weight to a certain extent in transit, but loss of weight may occur through pilferage or improper cooperage.
To detect this, packages can be examined for signs of tampering such as damage to the packing. Nails of packages, however, can be drawn and contents removed without leaving more than scratched, but even if nails have been skillfully removed and replaced they are often slightly loose or protruding. The examination of the package linings may also give evidence of pilferage for, if this has taken place, the lining is often damaged. There are, however, occasions when pilferages have taken place very skillfully without leaving any visible signs of tampering and the package can only be described as ‘Light in Weight’. Certain tea companies make a 10% check weighing at ports of shipment so that any pilferage of this type in the country of origin can be detected prior to shipment. On occasions chests of tea which have been pilfered have not shown any loss in weight but have been found to contain foreign matter as a ‘makeweight’.
Additional losses of weight can be sustained as a result of rough handling and improper cooperage in transit. When packages are coopered in the country of origin and at ports of shipment these are known as ‘Country Coopered Packages’. Those packages coopered on arrival at destination are known as ‘Dock Coopered Packages’. To ascertain where chests have been coopered the difference in the method and the material used for coopering is a guide. Often paper is placed between the damaged portion of the chest panel and the repair patch. The type of paper, which is usually newsprint, is also a guide for this purpose. Damage may occur for the following reasons:
- Pallets banding is insufficient to hold packages as a rigid unit.
- Pallets of poor design and/or quality cause collapse under strain in stow and during handling.
- Chests of 8-batten construction which have depleted structural strength, causing chests to collapse under pressure with banded units becoming slack.
Containerised Tea Shipments
Tea, in paper sacks, usually palletised, is generally carried in freight containers, which are of the standard dry type fitted with a pressure relief valve. It is not recommended that fully ventilated containers are used for tea shipments, but views differ on this. Prior to loading the container should be examined to eliminate the possibility of cross-contamination by timber flooring, etc. Tea for containerization is usually packed in multi-wall paper bags exported from certain countries. Where aluminium is used that lining should be in direct contact with tea. Pallets are shrink-wrapped when shipped from certain areas. The shrink-wrapping should not be air-tight, but should have regular air-holes to allow for interchange of air.
If wetting occurs in transit, water may enter through the holes in the shrink-wrapping and adversely affect the commodity, hence the progressions towards polyethylene of a higher strength in conjunction with aluminium. Tea which has suffered severe damage may be condemned as unfit for human consumption, in which case it can only be used for caffeine purposes.
- Mechanical influences
- Shrinkage / Shortage
- Insect infestation / Diseases