In the process of manufacturing there are different steps to be followed they are as follows :
1. Collecting the RAW MATERIAL
Two to three leaves and a bud is recommended as raw material for processing black tea in South India. The reason for the requirement of two/three leaves and a bud is due to the fact that chemicals which contribute to the quality contained in the tender leaves are in greater proportion.
Therefore, recommended shoot composition in South India for Quality Black Tea manufacture are:
Two/three leaves and a bud and single/two leaf banjis : 85%
Immature shoots : 5%
Coarse leaf : 10%
Over ten per cent of coarse leaf in the shoot composition:
Affects the chemical composition of the shoots.
Withers very slowly, leads to uneven wither which primarily causes flake and mixed infusion.
Complete maceration of coarse leaf is also difficult and results in improper cell disruption and poor fermentation.
2.WITHERING: (Physical/Chemical Withering)
Physical Withering is to remove the moisture from the green leaf and condition the leaf from turgid to elastic to facilitate better rolling. In addition to physical changes, the following bio-chemical changes occur to get better quality:
a. Polyphenoloxidase activity is increased which enhances the rate of fermentation.
b. Proteins are hydrolyzed to amino acid which is responsible for aroma of the tea.
c. Caffeine content is optimized which influences black tea quality.
d. Level of organic acids is enhanced which contribute to flavour of tea.
Quality surveillance steps during withering process:
a. Use ambient air when hygrometric difference is above 3ºC.
b. If the hygrometric difference is below 3ºC, use hot air with suitable proportion of ambient air.
c. The temperature of hot air should be below 35ºC.
d. To get even wither, the trough should be loaded with 2-3 kg/sq. ft. of green leaf.
e. Well ventilated lofts and access for drawing large volume of air is essential.
f. The ideal qualities of air for withering are low dry bulb temperature with high hygrometric difference.
g. Use reversible air flow system to get better withering and to avoid more handling of leaves manually.
h. Tapering cross section in the plenum chamber helps to maintain uniform pressure throughout the length of the trough.
The primary objective of rolling is to crush the leaf into small sizes. In addition, it presses out the juice and a thin film of juice is coated on the surface of the leaf particle to enhance chemical changes.
Quality assurance in the rolling process:
1. Use green leaf sifter to avoid jamming of machine.
2. Use leaf shredder to avoid over heating of dhool in the rotorvane.
3. A ball breaker is essential after the rotorvane, which will cool the tea before feeding into the CTC. Temperature of the rotorvane tea should not reach above 35ºC which reduces the enzyme activity.
To maintain zero-defect in quality, the following should be checked regularly:
a. The temperature after each cut-every two hours.
b. The size and style of the leaf from all the machines-every two hours.
c. The moisture content after shredding (70-72%) and after fifth cut (60%).
d. Magnet may be fixed on all the conveyers.
e. Ensure daily cleaning of CTC machine.
Fermentation is to bring about the chemical changes necessary to make tea liquor palatable. It is an oxidation process by which the rolled leaf looses its green colour and acquires copper colour. It also results in the formation of aroma of the fermented tea.
Error prevention process during fermentation
a. Co-current air flow arrangement is essential to supply more oxygen during the initial stage of fermentation.
b. The air should be fresh, cool and saturated with moisture.
c. The optimum temperature of dry bulb should range between 25ºC and 27ºC and the relative humidity of the air should be around 95%.
d. A post fermentation ball breaker is essential.
e. Fermenting drum must be cleaned with hot water or steam to avoid bacterial contamination.
The drying process arrests fermentation and reduces the moisture content in the fermented tea from 55-60% to 2-3%.
Key points for value-adding to quality, during drying:
a. Maintaining exact inlet and exhaust temperature is important to get uniform firing.
b. Proper loading of drier is also essential to get uniform firing:
Over loading causes back pressure and results in uneven drying.
c. Maintaining drying time and temperature is very important.
Longer the drying time – detrimental to quality & flavour.
Shorter the time – results in thin liquor.
Higher the temperature – results in bitter tea.
d. In the ECP drier, the optimum inlet temperature for CTC process is 100±5ºC, while exhaust temperature is maintained at 55ºC.
e. In the FBD drier, the desirable inlet temperature ranges from 120-125ºC, while the exhaust temperature is maintained at 60-65ºC.
f. Magnet can be fixed in the drier mouth, which will help in removing iron particles from made tea.
6.SORTING AND GRADING
Sorting is to remove fibre from the bulk tea and separate the tea particles into various shapes and sizes relevant to trade requirements.
a. Sorting enhances the appearances and quality of liquor.
b. Flakes of coarse leaf in the primary grade can be separated to avoid harshness.
c. Use of stainless steel meshes is desirable for good sorting.
d. Meshes should always be tight; loose meshes cause loss of bloom and uneven grading.
7. STORAGE AND PACKING
Black tea, being a highly hygroscopic material picks up moisture from the atmosphere, if packing is not proper.
a. Three per cent (3%) moisture level is advisable when packed – if the moisture content of tea reaches 6% the keeping quality is impaired.
b. Tea should not be stored in open condition.
c. Use of bins for storage of the finished product is very essential.
d. Tea should be cooled to ambient condition, before it is taken to bins.
e. Tea can be passed under powerful magnet grills to ensure iron free tea while packing.