Scientists in Japan have discovered that it might be possible to produce a tear-free onion without compromising on the taste. It had previously been thought that the tear-inducing effect that occurs when an onion is sliced was linked to the onion's flavour compounds. However, scientists from Japan's House Foods, reporting in today's [Thursday's] issue of the British journal Nature, have reported that a compound called propanthial S-oxide is responsible for the tear effect. The compound is produced by the appropriately named enzyme, lachrymatory-factor synthase, which is not responsible for the onion's flavour or nutritional value.