2. Post Harvest Technology :: Plantation Crop
Importance of Plantation Crops:
The term Plantation crops refers to those crops which are cultivated on an
extensive scale in a large contiguous area, owned and managed by an
Individual or a company. The crops include tea, coffee, rubber, cocoa,
coconut, arecanut, oil palm, palmyrah, cashew, cinchona etc. These plantation
crops are high value commercial crops of greater economic importance and
play a vital role in our Indian economy. The main draw back with this sector:
of crops in India is that major portion of the area is of small holdings (except
Tea) which hinders the adoption of intensive cultivation. In the case of coffee
97.13 per cent of the growers have holdings below ten hectares and in Rubber,
82 per cent of the total area is of small hojdings having an average size of 0.5
ha.
Eg: Tea
Tea is a beverage prepared by pouring boiling water over dry processed leaves.
Different factors affect the quality of tea like soil in which plant is grown,
climate, processing techniques used etc.
3. I. 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.
4. II. 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.
5. Quality surveillance steps during withering process:
a. Use ambient air when hygrometric difference is above 3ยบC.
b. If the hygrometric difference is below 3ยบC, use hot air with suitable proportion of
ambient air.
c. The temperature of hot air should be below 35ยบC.
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.
III. ROLLING
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.
6. 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
35ยบC which reduces the enzyme activity.
CTC MACHINE
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.
7. IV. FERMENTATION
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 25ยบC and 27ยบC 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.
8. V. DRYING
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 100ยฑ5ยบC, while
exhaust temperature is maintained at 55ยบC.
e. In the FBD drier, the desirable inlet temperature ranges from 120-125ยบC, while the
exhaust temperature is maintained at 60-65ยบC.
f. Magnet can be fixed in the drier mouth, which will help in removing iron particles
from made tea.
9. VI. 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.
VII. 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 โ 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.
