Both the nut (after processing), and the apple of the cashew are edible. The apple (the large fleshy fruit at the top of the nut) can be eaten at a stage when it is just ready to fall naturally. Care should be taken as the apple is very attractive to fruit flies. Some people find that their mouths blister from eating the apples so one should experiment a few times before eating any quantity of the fruit. Flavour of the apple varies considerably from tree to tree.
When considering the processing of the nuts it should be remembered that the shell of the nut contains a blistering caustic sap which is released if the shell is damaged in any way. Do not attempt to crack the unprocessed nuts.
The processing consists of roasting the nuts at 350 - 400°F (180-200°C) for 10 - 20 minutes on fine sand to extract the caustic cashew nut oil. The oil may spurt from the shells when the nuts are heated. During this initial roasting the sand will take up the oil and also prevents the oil from spurting. Never attempt this initial roasting without first either covering the nuts with sand, or else having a lid on the container.
The temperature used for roasting has to be hot enough to cause the oil to exude from the shell of the nut but not hot enough to cause the kernel to dry out. Temperatures of 450 - 500°F (230 - 260°C) will cause the oil to vaporise and issue as a choking cloud from the oven as well as causing the kernel to dry out.
A small amount of experimentation may be needed to obtain the exact temperature and time needed for oil extraction.
Care should be taken to inhale a minimum of the fumes given off during roasting.
Preferably use an old dish when doing the initial roasting of the nuts as the oil may be difficult to remove from the dish after the baking is finished.
After the initial roasting, the nuts are sieved out of the sand and washed in water and detergent to remove the final traces of oil. Care should be taken not to wipe your face or eyes with your hands while washing or cracking the nuts, because of the possible residue of caustic oil.
The nut is then cracked and the kernel freed of the thin brown skin. The final process is roasting the kernel in coconut oil at 300°F (150°C) for 5 minutes.
Wine can be made from the cashew apples in the same way as wine is made from other fruit. It is a somewhat involved process and anyone wishing to make wine should consult or join a local Wine Makers Guild.
DATE: July 1983
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