Cashew nut trees, though originally native to Brazil, have spread all over the tropical world and today, the major producers of cashew include Nigeria, India, Vietnam and the Ivory Coast. The key differentiator about the cashew nut is the fact that the nut appears outside the fruit. The cashew fruit is also called as cashew apple and the nut appears outside the fruit. The cashew nut is the seed and this is surrounded by a double shell. In order to finally reach the seed, which is the cashew nut, these shells have to be removed and this involves systematic processing.
The steps involved are
- Cleaning
Initially, the raw nuts are cleaned and dirt, sand, stones and any other particles and foreign matter are removed.
- Drying
After cleaning, the nuts are dried in the open sun, in order to eliminate the moisture. In order to ensure that the nuts are dried on both the sides, they have to be rolled over on a regular basis. The drying process happens under the sun, usually in an open yard.
- Roasting
The outer shell of the cashew is extremely hard and needs to be softened. This is done by means of the roasting process. Here, the cashews are roasted in a cooker, which is supplied with steam from a boiler. The roasting time depends on the nature of the cashew and is judged based on experience.
- Cutting
Once the outer shell is softened, it is cut. The cutting process can be manual as well as automatic. In the case of automatic operation, there are special machines which do the task. But the blade setting is highly critical, to ensure that inner kernel is not affected. The manual method involves the use of either hand or leg operated machines. There is a greater control in this process and a higher percentage of kernels come out undamaged. However, great care needs to be taken, since the shell contains an allergic resin. This can be dangerous, if not properly handled.
- Drying in a hot chamber
Even though the outer shell of the cashew has been cut, there is an adhering seed coat or testa. This has to be removed. Since this seed coat is closely held on to the seed, the only way to remove this will be by drying in a hot chamber. Usually, the cashews are held in trays and hot air from a blower is passed over them. The temperature maintained is usually about 75 to 80 degrees Celsius. Once the testa is softened, further processing is easy.
- Peeling
In this stage, the testa is peeled. Although in the past, the manual method of peeling was used, this has now been mechanized. The most commonly used method is to blow the testa away by means of high pressure air. This will ensure testa removal without any damage to the kernels. Other methods employed include freezing, suction, passing the kernels via rubber rollers, etc.
- Grading and Packing
Finally, the kernels are graded. The broken pieces are separately sorted and the whole kernels also sorted based on their shape, colour and other parameters. Packing of different grades is done in a hygienic environment and the cashews are ready to hit the market for consumption.