After shelling, shell pieces and kernels are separated and the unshelled nuts are returned to the shelling operation. Usually blowers and shakers are used to separate the lighter shell pieces from the kernels. The greatest problem is to recover small pieces of kernel sticking to the shell. This is usually done manually from a conveyor belt used to carry all the sorted semi-shelled nuts.
 Pre-grading can be done before or after drying the kernels and may greatly reduce the final grading work. For large-scale processors pre-grading can be done mechanically, separating mainly the whole from the broken kernels and sometimes separating the different size groups of whole kernels.

The shelled kernel is covered with the testa and to facilitate removal, i.e. to peel in order to produce the blanched kernel, the shelled kernel is dried. This also protects the kernel from pest and fungus attack at this vulnerable stage. The moisture content is approximately 6% before drying and 3% after. It is important that the drying capacity is higher than the shelling capacity in case of periods of heavy rainfall because the drying operation will be lengthened since the kernels will absorb the moisture very quickly. Sun drying, where the kernels are spread out in thin layers under strong sunshine is possible, however artificial drying becomes necessary for medium or larger-scale producers. 

Drying usually takes six hours, at a temperature of around 70?C. A uniform temperature throughout the drier is essential to avoid under drying or scorching. Figure 5 and 6 shows a Practical Action tray dryer, details of which are available on request. 
It is in the dried condition the kernels are most vulnerable, being both brittle and susceptible to insect infestation. Therefore, at this stage, they must be handled with care and moved to the next stage of peeling as quickly as possible.

At this stage, the testa is loosely attached to the kernel, although a small amount of kernels may have already lost the testa during the previous operations. Manual peeling is done by gentle rubbing with the fingers. Those parts still attached to the kernel are removed by the use of a bamboo knife. One person can peel about 10-12kg of kernels per day.

 The mechanised processes of peeling differ widely. They include air-blasting, suction, a freezing operation and a system of rubber rollers. The operation has a low efficiency due to the difficulty of removing the testa and the amount of breakages can be as high as 30%. Currently research and development is taking place to improve the viability of the mechanisation of this operation. 

The grading operation is important as it is the last opportunity for quality control on the kernels. With the exception of a few grading aids, all grading is done by hand. Power driven rotary sieves are one mechanical method, another being two outwardly rotating rubber rollers aligned at a diverging angle. For large operations looking towards export markets, it is necessary to grade the kernels to an international level.

Rehumidification before the kernels are packed it is necessary to ensure that their moisture content rises from 3% up to around 5%. This is to make the kernels less fragile, thus lessening the risk of breakage during transport. In humid climates, the kernels may absorb enough moisture during peeling and grading to make a further rehumidification process unnecessary.


The normal packaging for export of kernels is in air-tight tins of 25lbs in weight. The packing needs to be impermeable as cashew kernels are subject to rancidity and go stale very quickly. The tin will be familiar to most tropical countries as it is a replica of the four gallon kerosene or paraffin oil tin. If possible the tins are made locally as movement of empty tins overseas is expensive. Alternatively, it might be arranged to purchase components and finish the manufacturing locally. 

 This may be done by arrangement with tin manufacturers. The output of a tin manufacturing line is usually too large for one consumer but some cashew nut processors have in fact installed their own tin making plant and supply other processors.
After filling and weighing, the cap should be soldered on in preparation for the 'vita pack' process. This consists of removing all air from the tin and substituting this with carbon dioxide (CO2). The advantages of packing cashew kernels in carbon dioxide are twofold. Firstly, carbon dioxide is an inert gas and will not support life. Any infestation that may have been present is therefore arrested. Secondly, carbon dioxide is soluble in cashew oil and goes into solution as soon as the seals are made. In a short space of time, it can be seen that a decrease in pressure takes place as the carbon dioxide goes into solution and the sides, top and bottom are drawn inwards. Thus the kernels are held tight in the tin, preventing movement and breakage during transport. Carbon dioxide, being a heavy gas causes the upward displacement of air and will remain in the tins after the filling process. Some large-scale machines will operate on six tins at a time, creating a vacuum in each and then filling with carbon dioxide.
Some processors do not have vacuum pumps and displace the air in the tin by feeding in carbon dioxide through a small hole in the bottom of a side of the tin. The carbon dioxide valve is turned off when all the air has been replaced. The holes in the tin are then sealed, with the hole at the bottom of the side of the tin being done first, and the one on the top last.

Far too little attention is paid to the infestation hazards of cashew kernels. These hazards are more prevalent at some times of the year than others; however a good processor will be vigilant all the time. The main insect pests are:
* ants
* grain weevils
* meal moths

 The most important defence against infestation of any type is cleanliness and is essential in the rooms used for drying, peeling, grading, conditioning, and packaging. Floors and walls must be sound and free from cracks. They should be kept white-washed regularly. Some processors have filled the corners and places where the wall meets the floor with a curved filling so that the room can be properly swept, all corners having been eliminated.

Speed of operations between drying and packaging must be stressed as this reduces the critical period when attacks may occur to a minimum. The equipment used must also be thoroughly cleaned on a regular basis as insects may breed in hidden crevices and gaps.

Cashews originate as cashew fruits; the shell of the fruit is taken off and the thin skin peeled off from the nut inside before we get the kernels we call cashew nuts. Thus, raw cashews refer to the cashew fruits as they appear on the trees, and the proper term for cashew nuts is cashew kernels (cashew nuts should do as well).

The shell that is taken off from the fruit can be used as well - to produce what is called CNSL (for cashew nut shell liquid), a liquid that is used in a variety of industries for resin & chemicals (cardanol, residol, cardol & anacardic acid) that are derived from it. A less valuable use of the shell is as a fuel.

In rare cases, oil is also be derived from the cashew kernel (as opposed to the liquid derived from the shell). This oil, called cashew oil, is edible. CNSL is not, it is poisonous.

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