Genetically modified foods, currently fuelling fiery debates across the world, could help to make the life of the cook more pleasant. In a new study from Japan, researchers claim to have identified the enzyme that releases a tear-duct-tickling chemical when an onion is cut.
Shinsuke Imai of the House Foods Corporation in Chiba, Japan, and colleagues have discovered that the tear-jerking compound in onions, called propanthial S-oxide, is made by an enzyme known as lachrymatory-factor synthase.
Previous studies had suggested that onions' flavour compounds were behind the effect. Chopping was thought to make them react with a common onion enzyme, allinase, producing propanthial S-oxide, reports science journal Nature.
This suggested, continues the magazine, that in order to breed or genetically engineer a non-irritant onion, scientists would have to tamper with its flavour.
"The chemistry is not new," said Richard Dixon, a plant geneticist at the Noble Foundation in Ardmore, Oklahoma. "But the way it occurs in the plant is not as was first thought."
The Japanese scientists suggest that now that a single, flavour-independent enzyme has been identified, it would be simple to create an onion in which the enzyme was absent, or suppressed.
The Nature report highlighted the fact that although a tear-free onion is not exactly a key need in today's society, it could be important in that the onion could be one of the first GM organisms acceptable to consumers. It does not require the addition of a foreign gene, simply the silencing of an existing one.
Full findings are published in the latest issue of Nature, 419, 685, (2002).