Lovely to eat but poisonous if not handled properly
Text by Gregory Leow @ Makansutra
Many know that famous Peranakan chicken stew dish, ayam buah keluak, or the Indonesian Nasi Rawon, made with the goodness of the keluak black nut which is rich and oily, and bears more than a passing taste resemblance to a smoky mushroom or strong-flavoured truffles. Like the durian, it is definitely an acquired taste.
However, many people do not realise that if you pluck a buak keluak fruit straight from the tree, strip off the flesh and start using the seeds to make dishes, you may be treating yourself to the same poison that Nazi German soldiers used to gas their enemies in World War 2.
Native to the mangrove swamps in Southeast Asia, the buah keluak tree’s (Pangium edule/keluak/ keluwak/kepayang) wood, leaves, fruit and seeds all contain a glycoside compound that converts to hydrocyanic acid, also known as cyanide.
If you have ingested enough cyanide, its effects can be general weakness, confusion, excessive sleepiness, coma, shortness of breath, headache, dizziness, and seizures, before unconsciousness sets in. Concentrated levels will cause cardiac arrest and death.
seeds bought from the market have their poison extracted and you can buy shell and nut separate if you'd like.
Luckily, dried food stallholders who sell the buah keluak seeds (stripped of fruit) – in places like Tekka or Geylang Serai markets – tell us that the seeds are already extracted of poison by a variety of processes like soaking, boiling or burying in ash.
But to be on the safe side, once you have bought the seeds, the practise is to soak the nuts in large tubs of water for at least four to five days, changed twice a day, not only to extract any remaining poison but to get rid of the raw taste of mud.
It is also to soften the shells so that it is easily cracked and you can get better access to the delicious black nut that we all love.