Warning to the public! The following may stop you from eating the very delectable rambutan fruit forever! The yummy and juicy flesh is perfectly safe but the outside peels and inner seeds are of different story. It contain poisonous substance.
Seed testa have nephelium saponin and tannin. The compounds tannins and saponin have dual sided reputation, usefullness in medicine and other industries and the dangers of being toxic. Tannin is one of the healthy compents of wine. It is known to have antiviral, antibacterial, antiparasitic, anti-inflammatory and antiulcer effect. Plant saponin is commonly used as fish poison and have some medicinal benefits as well.
No recorded deaths due to eating of rambutan seeds and peels.
Bitter and toxic when raw but edible and safe when roasted. I tried biting a seed before knowing the fact that it is poisonous. I only sensed very slight bitterness. I chewed raw peanut too and never detected any noticeable difference. I have never tried roasting it yet.
Another way to cook the seeds is by removing the seed coat or testa, boiling in water until soft, then boiling in syrup to make sweet.
Contains tallow similar cocoa butter. About more than 37% of seed is tallow. Tallow is gathered by cold pressing method. Useful for making soap and candles. Maybe a rambutan seed chocolate is possible. Not sure! I hope a can gather enough seeds to do a little crazy experiment.
Seeds are known to lower blood sugar level, expel intestinal worms and tone muscles.
The fruit skin is also known to have toxic saponin. Need to dig further details about…
Rambutan seed composition by Augustin, M.A. Chua, B.C. 1988
37.1-38.9% crude fat – pet ether extract
2.8-6.6 crude fiber
2.6-2.9 dry ash on dry weight basis