The key ingredients are light-emitting enzymes found in deep-sea jellyfish, squid and shrimp.

These enzymes are produced by the deep-sea creatures to illuminate their pitch-black surroundings, but have many other uses.

Scientists are already investigating them as possible new technologies for data storage in computers.

Master technique

Prolume, a Pittsburgh-based company, has worked with biochemist Tony Campbell, of the University of Wales, to master the technique of using the enzymes.

Together they isolated these natural compounds and added them to a range of foods. Tests show the compounds are flavourless and appear to be harmless.

The company's President, Gene Finley, said: "We have done one to three-month toxicology studies in rats and they seem to be safe."

Dim the lights

Campbell said the chemicals could illuminate a product for up to half-an-hour. "You would need to dim the lights to see it - but it could be ideal for a birthday cake," he said.