The system could also have medical uses for identifying cancerous cells remaining after surgery, said Tony Campbell of the University of Wales, who is working with Prolume, a Pittsburgh-based company. "You would add these chemicals to the body and the cells would turn red or blue, depending on whether they were cancerous or not," he said yesterday.
Professor Campbell, a medical biochemist, is a partner in Prolume, which this week demonstrated foods incorporating flavourless "bioluminescent" chemicals.
Tests on animals indicate that the substances appear to be harmless. Gene Finley, the company's president, said: "We've done one- to three- month toxicology studies in rodents and it seems to be safe," he said.
The Prolume system combines enzymes produced naturally by deep-sea animals that have to generate their own light because sunlight cannot penetrate to the depths they inhabit. The Prolume team has isolated the genes that produce the enzymes.
Professor Campbell said: "For a cake or drink, you would add a chemical to make it luminous, and that would last for some minutes - perhaps up to half an hour. You would need to dim the lights to see it - but it could be ideal for birthday cakes."
A cancer detection system is still some years off, but Professor Campbell reckons that success in the consumer market for Prolume could help fund such important medical uses.
Anyone worried that food which goes in luminescent might emerge the same way has no cause for concern, said Professor Campbell. "The active proteins would get degraded during digestion, like any other," he said. "Though I suppose we would have to investigate that."