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PROCESSING OF CASHEWNUT
Processing of cashewnuts refers to the conversion of raw cashewnuts in shell to its blanched graded kernel form. The processing units are mainly concentrated in the states of Kerala, Tamil Nadu, Karnataka, Goa, Andhra Pradesh, Maharashtra and Orissa. The process is highly labour intensive and the work force consists mainly of women.
- Drum roasting
This is one of the oldest and more widely used methods. The nuts are fed into a rotating red hot drum which will ignite the shell maintaining its temperature because of the burning of the shell liquid. The drum is kept in rotation for 3-4 minutes and the roasted nuts are discharged from the lower end of the drum and immediately covered by ash after sprayed with little water, so as to absorb the oil on the surface. This facilitates the removal of the remaining oil on the shell. Due to draw backs of the method is superseded by oil bath roasting.
- Oil bath roasting
In this method conditioned nuts are passed through CNSL bath heated to 170-2000C by conveyer buckets for 1-2 minutes during which period the shell gets heated rupturing the wall and releasing the oil into the bath. The oil is recovered by continuous over flow arrangement. The roasted nuts are centrifuged to remove adhering oil, cooled and shelled by hand and leg operated shelling machines. The kernel with the adhering testa is scooped out using a sharp needle.
- Steam roasting
The raw nuts are steam cooked at about 120-140 lbs/sq inch pressure. Shell oil can be extracted in later stages by crushing. The nuts are shelled by hand and leg operated shelling machines.
A general comparison of the above three methods would show that the oil bath method and steam roasting systems require more initial investment and higher maintenance costs: the drum roasting method being the cheapest. From the point of view of environmental pollution the safest is the steam roasting method.
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