Cashew nuts tree

3 De Smet plants are designed for processing cashew nut.

Origin

The cashew nuts tree (Western Anacardium) grows naturally or by culture in South of India, in Brazil, in Nigeria, in some subtropical countries and mainly in Mozambique.

End uses

The tree, right, very thick and very branchy, with a height up to 10 m., produces :
- wood, locally used for manufacture of boxes, ships, charcoal, ...
- the sap used as varnish, insecticide, and in chemistry
- the bark, rich in tannin, from which we extract by soaking a paint used to waterproof the fishingman clothes, ...
- the leaves appreciated in medicine
- the cashew nut

The nut, due to a very growing use in industry, meets increased interest in the production countries.
The cashew nut is a very particular fruit. With a form of a small kidney of 2 to 3 cm long, it grows on the tree at the base of a seedless fruit, which has the aspect of a yellow pear, called cashew apple and used locally in the preparation of refreshing drinks and of vinegar.

Composition

The nut contains about 30% of almond and 70% of shell. The almond, long and curved, has a very fine taste; grilled and salted, it is appreciated as on appetiser. A butter can be extracted as well and is used in cookies.

The shell, very hard, with a thickness of 1 to 2 mm contains in its cells, a natural resin called CNSL (cashew nut shell liquid) of a hard chestnut brown colour, very viscous, vesicatory and caustic
This liquid represents 25 to 35% of the shell weight; it contains 90% of anacardic acid C44 H30 O5 and 10% of cardol C42 H31 O4.

The growing demand and the multiple uses of CNSL make its value increase; but anyway, the cashew nut itself represents still the more valuable part of the production.

CNSL Extraction Methods Process

The cashew nuts have firstly to be decorticated in order to treat shells and almonds separately.
Most of the time the decorticating is still done manually, but a good worker can only treat 5 kg of almonds per 8 hours. India having abundant and cheap labour processes not only its own production but also imports large amounts.
To crack the nut, a roasting at high temperature during a few minutes is necessary in order to make it fragile but without burning the almond.
To improve decorticating, it is necessary to humidify the nuts. The optimal conditions seem to be at 25% of moisture and a fast roasting of 2 minutes at 180°C. It is performed in a frying bath and then the nut is rapidly cooled by water spray; the frying bath enriches itself by CNSL exuded.