Palm oil is the second largest
edible oil in the world. It is a tropical crop and is grown maximum in
southeast Asia, West Africa and Latin American countries. The fruit is
obtained after threshing which is done both by hands and machines. In
mechanized threshing system a rotating drum with rotary beater detach
the fruit from the bunch. The fruits now ready for processing is
processed by using following machines :
- Sterilizer
Sterilization is a process of wet-heat treatment of loose fruit.
Sterilization uses pressurized steam. The hot steam from sterilizer
causes the moisture in the nuts to expand. The reduction of pressure
leads to the contraction of nuts which further results in the
detachment of the kernel from the shell wall. This detachment
facilitates later nut cracking operations.
- Digester
Through digestion process, the palm oil is released in the fruit
through rupture. The digester normally consists of a steam-heated
cylindrical vessel along with rotating shaft having number of
stirring arms. Beater arm pound the fruit. This helps in reducing
the viscosity of oil and completes the disruption of oil cells begun
in the sterilization phase.
Palm Oil Pressing
There are two types of presses :
- Batch press
In batch press material is pressed by using plunger metal. The
plunger are either moved manually or by a motor. Presses that are
used are either spindle press or hydraulic press to move the
plunger. Higher pressures may be attained using the hydraulic
system. Spindle press screw threads are made from hard steel and
held by softer steel nuts so that the nuts wear out faster than the
screw. Hydraulic presses are faster than spindle screw types and
powered presses are faster than manual types.
- Continuous press
Continuous press consists of a cylindrical perforated cage through
which runs a closely fitting screw. Digested fruit is continuously
conveyed through the cage towards an outlet restricted by a cone,
which creates the pressure to expel the oil through the cage
perforations.
Clearing of oil
The extracted oil is first diluted with water then heated and finally
decanted to obtain clear and dirt free palm oil.
