The plucked
leaves from the fields are collected in rattan baskets or nylon bags with large
perforations so that the leaf is aerated. These are then transported in lorries
or trucks and sent to the factory for processing. Medium to large plantations
normally have their own factories.
Withering
Withering is the process of removing part of the intrinsic moisture content
of the leaf so as to render same flaccid i.e the leaf is twistable without breaking.
The leaf entering the factory is spread evenly on troughs, commonly called withering
troughs. During that time, dry air is blown through the spread leaf. Warm air
is induced sparingly when there is surface moisture on the leaf. Withering varies
with the material and an even wither is directly related to the style and plucking
standard. The coarser the plucking, the less chance there is to obtain an even
wither as a harder epidermis (skin) takes longer to lose its moisture. Withering
takes about 8 hrs to 15 hours depending upon the condition of the leaf in relation
to the prevailing weather conditions.
Processing
There are different means of processing the leaf but the most common one is
the Rotorvane – CTC. The withered leaf is fed into a Rotorvane, which
crushes the leaf by building pressure in itself. The crushed leaf is then fed
through a bank of CTC machine (Cut, Tear and Curl). During this process, as
the name of the machine indicates, the crushed leaf coming out from the Rotorvane
are cut into small sizes, the cells in the leaf are ruptured and exposed by
the tearing effect and the cut pieces are curled to give a grainy make of tea.
When the leaves are ruptured during rolling, the polyphenols and oxidase mix
and oxidation starts if oxygen is present.
Fermentation
Fermentation is a process of oxidation. There are different methods to carry
out the fermentation process but the most common one is the continuous fermenting
table. The crushed leaf coming out from the CTC process is spread evenly over
a continuous moving table. The essential factor in fermenting is that sufficient
air must be made available to the crushed leaf for the purpose of oxidation
and the removal of carbon dioxide. During fermentation there are various enzymatic
actions taking place and heat is generated. If the temperature is too high,
oxidation is uncontrollable and if the temperature is too low, fermentation
does not take occur. During fermentation ‘Theaflavins’ and ‘Thearubigins’
develop which contribute to the golden yellow colour of fermented leaf. This
process, depending upon several other parameters, generally takes about 60 minutes.
It is during this important process that certain characteristics of the tea
such as briskness, brightness, colour and hardness is developed.
Firing
Firing is commonly known as Drying. The main purpose of drying is to arrest
fermentation and to reduce the moisture content to a level which gives a keeping
quality to the dried tea. Special equipments called Dryers are used to fire
the teas. A thin even layer of the fermented leaf is continuously fed into the
Dryers. Controlled hot air is blown into the dryers and in turn passes through
the fermented leaf. Depending upon several other factors, generally the drying
process takes about 20 minutes.
Sorting
Sorting is a process of cleaning and grading the fired teas by passing them
over electrostatic fibre extractors and wire meshes of different apertures.
The graded teas are then stored in airtight bins for packing.
Packing
Depending upon market demand the stored teas are packed in either paper sacks
for export or small packets and tea bags mainly for the local market.
Types
of tea manufactured
The raw
green leaf has, for years, been processed into three different classes of tea.
The quest for ‘fast food’ in modern times has given us a fourth
class – Instant Tea, commonly called as Soluble Tea, which is a powdery
form and is popular in the West, especially USA. Each of these classes is produced
from a different manufacturing process though they originate from the same plant.
- Black tea
- Green tea
- Oolong tea
- Instant Tea/Soluble tea
Black
Tea
Green
tea leaf is crushed, torn and curled (CTC) or rolled before being fermented
and dried into black tea.
Black
tea can be of two types:-
• Orthodox
• CTC
Orthodox
black tea is manufactured in the traditional manner, while ‘CTC’
was born after the invention of the ‘Cut-Tear-Curl’ machine.
Green
Tea
Green
Tea is the least processed of all tea types. As soon as the leaves are
plucked from the plant they are steamed or pan fired in order to arrest
the active enzymes that cause oxidation from occurring. As a result of
this process the leaves maintain a soft and supple texture that ultimately
get rolled into the desired shape. Once rolled, the leaves continue through
another rolling, pan firing, or heating process until the tea reaches
4% or less of moisture.
Oolong
tea
Oolong
tea is an intermediate type between black and green tea and undergoes semi-fermentation.
Instant
Tea
Instant
tea is soluble tea similar to instant coffee. It can be utilized directly
without any infusion as for “traditional” tea. The caffeine
content in soluble tea is 40 mg per cup as compared to 60-70 mg per cup
for ordinary tea. Instant tea is also known as soluble tea or powder tea.
Development
of Instant Tea. Instant tea has recently become of urgent practical importance
largely because of the success of instant coffee and the sale of beverages
from vending machines. Instant tea is also used for iced drinks. An advantage
of instant tea is that there is no waste in the household as compared
to the waste from infused tea.Instant tea can be made from infusion of:
Manufactured
tea
Fermented and undried leaf
Fresh green leaf
In all
cases the infusion is evaporated and dried by freeze drying, spray drying
or vacuum drying. When the process is completed, only a powder remains.
Low temperatures are used to prevent loss of substances responsible for
flavour and aroma of tea.
