3. Coffee flowers are white and sweet smelling,
producing green berries which turn red when ripe.
The berry contains a mucilaginous pulp with two
greenish grey seeds or beans, each covered by a
thin membrane, the silver skin, and both are
enclosed in a common husk-like membrane or
parchament. Sometimes a single bean fills the berry
instead of two, when the seed is called a peaberry,
since it is like a pea. The berries are picked when
ripe. Unripe berries give defective beans (Triage)
and overripe ones are difficult to beat to a pulp.
• Coffee processing consists of removing the skin, pulp,
parchment and silver skin.
• The quality of the final product depends upon the
manner of processing.
• • Two methods are employed for processing:
1. Dry Method
• In this method, the berries are sun dried by spreading
them out on drying floors and the coverings are removed
by hulling. The beans are later cured in curing sheds. The
product obtained is known in trade as cherry or native
5. 2. Wet Method (washed coffee
• In the wet method, the ripe fruits are squeezed in a pulping
machine which removes the soft outer pulp, leaving a
slippery exposed layer of mucilage.
• The mucilage is removed by spontaneous fermentation.
This is sometimes facilitated with added enzymes.
• The seeds separating from the pulp are washed and
subsequently dried to a moisture content of 12 per cent.
• The wet method gives better quality coffee with a bluish-
green colour (green coffee).
• The green seeds are then graded and packed.
• Green coffee may be stored for prolonged periods with no
6. • Each variety of coffee has its own flavour and
other characteristics. Generally, marketed
coffee is a blend of different varieties of coffee
• The blends are controlled for flavour, aroma,
colour and strength or body of the beverage
from the roasted bean.
• Raw or green coffee has no flavour or aroma and
has an unpleasant taste. For use as a beverage, it
is roasted, powdered and brewed and the
aqueous extract used as a beverage with or
without the addition of milk, sugar and other
• During roasting many physical and chemical
changes occur. The beans swell in size to almost
double their original size, the dull green colour
changes to brown and the characteristic coffee
aroma develops. The beans lose their hard horny
structure and become brittle, with the outer
surface still smooth and firm.
8. • During roasting, pressure develops in the beans, and
this appears to be necessary for the proper
development of coffee flavour. It is said that pressure
holds the initial breakdown products together until the
proper stage of roasting is reached, when they react
with each other to produce coffee flavour.
• The flavour is due to a mixture of numerous
components rather than a definite chemical entity and
is apparently produced during roasting. Some moisture
is lost during roasting and carbon dioxide is produced
in a comparatively large quantity, some of it escaping
and some being absorbed within the texture of the
9. • Carbohydrates decompose, caramalize and,
perhaps in combination with other
substances, contribute to the aroma of the
beverage produced from the roasted beans.
• Fatty constituents are also affected, volatile
fatty acids are driven off and complex fats and
waxes are cracked to form simple ones.
• Proteins may be hydrolyzed and give cleavage
products. There is little change in the caffeine
content of coffee during roasting.
10. • The flavour of roasted coffee, to a large extent,
depends upon the manner and extent of roasting.
• The flavour and aroma of coffee are best. when it
is freshly roasted and deteriorate on standing.
• Coffee exposed to air changes more rapidly than
coffee not exposed. The staleness of coffee
exposed to air is due to the oxidative changes
that take place with certain coffee constituents.
This is prevented by the presence of carbon
dioxide in roasted coffee. On storage, carbon
dioxide is lost and so are the flavour and aroma.
11. • Moisture also has a profound effect on the
flavour of coffee. Coffee exposed to moisture
loses all its flavour in a relatively short time.
• The loss of flavour in vacuum packed coffee or
coffee packed under pressure using carbon
dioxide is less. Since the loss of flavour and aroma
is more in ground coffee than in beans, the
roasted beans should be freshly ground to obtain
quality coffee. In spite of many investigations, it
has not been possible to clearly understand the
many complex physical and chemical changes
taking place during the roasting of coffee beans.