The quality of tea is broadly judged on a combination of factors, like aroma/flavour, strength, colour, briskness and character of infused leaf.
Tea quality varies not only from one estate/garden to another, but also between the same grade/type of tea manufactured at different times from a particular garden.
The main factors that affect the quality of tea are:
- Genetic properties of the cultivar, the tea plant and tea bush.
- Soil and climate conditions, including temperature, humidity, sunshine duration, rainfall, etc.
- Field operation such as pruning, fertilising, shading, plucking round and plucking standards.
- Processing – the processing of tea from the plucking to the grading stages has a huge impact on the manufactured product.
THE PROCESS
Tea manufacture is the process of transformation of freshly plucked green tea leaves to black tea.
The process itself is long, requires much care, attention, control and a scientific understanding of the complicated physical and chemical changes in the leaf as the manufacture progresses.
There are several distinctive processes that take place in the manufacture of black teas.
PLUCKING:
The green leaf is harvested on a regular basis at intervals ranging from 5 days to 8 days from each field. The plucking of the soft two leaves and the bud is generally undertaken by well trained women, because of the agility of feminine hands. The manufacture begins from the time the leaf is plucked in the field, and to ensure it retains its freshness, the leaf is sent to the factories from the fields three to four times a day.
WITHERING:
No sooner it is received at the factory, the leaf is weighed and spread on troughs. Withering, is a process, where conditioned air is circulated between the leaves, initially to remove any surface moisture and thereafter to concentrate and chemically breakdown the tea juices. It takes 10 hours to 14 hours for the physical and chemical changes to take place, and bring the leaf to soft and rubbery condition suitable for the next stage of manufacture.
ROLLING:
Is the process by which the leaf is twisted and the leaf cell walls ruptured to bring the juices to the surface of the leaf. The rolling machines have deep jacket, a pressure cap to apply pressure on the leaf, and the table itself has battens and a cone at the center to twist the leaf. There are also the more modern “Rotorvane” machines, which also give the same twisting and turning effect. This process takes about 20 to 30 minutes.
Thereafter to separate the twisted leaf from the untwisted, and to reduce the heat build up, the rolled leaf is passed over a roll breaker. This machine has meshes which separate rolled leaf. The unrolled is put back into the rollers for further rolling whilst the rolled leaf is fermented.
FERMENTATION:
Of the tea juices is an essential process in the manufacture of black tea. Fermentation is the oxidization of the enzymes in the juices, which bring out the flavour, strength and the colour of the liquors and infusions. Fermentations is generally carried out on glass or tiled tables.
As fermentation progresses there is a colour change of the leaf from greenish to coppery brown. The degree of fermentation is judged by the colour and aroma.
DRYING:
The primary objective of drying is the extraction of moisture and the arresting of fermentation. The fermented leaf contains from 45% to 50% moisture. The leaf is passed through driers, which have circuits of trays with perforation, on which are conveyed the fermented leaf.
The drying process takes about 20 to 25 minutes and the initial temperature is about 120 Degrees F(50 Degrees C) and is finished off at a temperature of 200 Degrees F (93 Degrees C) to 220 degrees F (105 Degrees C) . The moisture content of the teas when drying is completed is approximately 2% to 3% and the coppery brown fermented tea particles are now back.
GRADING (SIFTING):
The fired teas after cooling are graded / sifted according to size and shape, as the trade demands. The different grades of tea are identified nomenclature. On completion of the grading, teas are stored in airtight bins of boxes. The sifting is carried out on a series of grading and cleaning machines, which have several trays of different mesh sizes, to separate the tea particles to the various grades of tea and to remove the stalk and fibre.
PACKING / DESPATCHING:
Teas are very hygroscopic and rapidly absorb moisture. When sufficient quantities of teas are collected, the are either packed in plywood tea chests of multi-walled aluminum craft paper lined pager sacks and despatched to the auctions or packed into tea packs of various forms for direct export/distribution.