Japanese researchers have discovered that it might be possible for tear-free GM onions to taste like onions. They have also found that the chemical in onions that makes you cry is not related to flavour. Researchers at the House Foods Corporation, University of Tokyo and Kyoto University,tested the theory that the crying response to onions was caused by an enzyme called alliinase. Alliinase plays a part in the chemical reactions that give onions their flavour.
In their experiment, the researchers used alliinase extracted from garlic to determine whether it caused crying (in a reaction called the lachrymatory factor because the lachrymal gland in the eye produces tears). When it did not, they investigated other potential candidates.
To their surprise, they found a hitherto unknown enzyme called lachrymatory-factor synthase was responsible for making a compound called propanthial S-oxide which causes crying.
They were also surprised to discover that when this enzyme was removed more thiosulphinate was produced - thiosulphinate is the compound that gives fresh onions their flavour.
The researchers claim that it may be possible to develop a tear-free onion that still retains its characteristic flavour and high nutritional value by decreasing the activity of the lachrymatory-factor synthase.