My father used to harvest half-ripe sugar palm fruits. Immediately after picking, they were boiling the fruits to give it a soft jelly-like consistency. It is then pricked out with a short sharp stick. Soaked and washed in several changes of water for few days. The jelly-like flesh called “kaong” was ready for market. It is use for sweet delicacies.
However, that’s not the main issue . Then process mentioned above always make my body very itchy. They told me to stop talking while the process is on-going. Talking makes me feel itchy? I guessed not.
Half-ripe sugar palm fruits contains high levels of irritating oxalate crystals, calcium oxalate. It is a chemical compound that forms needle-shaped structures. It plays an important role in development of kidney stones. Some oxalate containing foods are sweet potatoes, black indian tea, okra, chocolate, soybean crackers, peanuts, swiss chard, wheat germ, spinach, beets and rhubarb.
Oxalate crystals is poisonous when ingested. Even small doses of oxalate toxin is enough to cause intense sensations of burning in the mouth and throat, swelling, and choking. Larger doses cause severe digestive upset, breathing difficulties, convulsions, coma and death. Recovery from severe oxalate poisoning is possible, but permanent liver and kidney damage is irreversible.
You don’t have to worry . Oxalate crystals reside only on walls and stalk of fruits. The processed “kaong” is safe to eat. Itching can be prevented by wearing gloves and long sleeves while processing.
updated: May 2017
Medscape.com has clearer explanation regarding calcium oxalate. It is a water insoluble salt that forms a bundle of needle-like crystals called raphides. Contact with moisture causes plant cells to eject these raphides, which may come contact with skin or mucosal surfaces. Raphides longer than 180 micros are believed to be more potent. Upon skin contact, they allow entry of other irritant such as proteases, saponins etc.
So calcium oxalate is like a bunch of tiny thousand arrow traps dabbed with toxin. Water serves as trigger. Piercing effect hurts. Added toxins magnifies pain several times.