Volunteers taste fat under Professor Deakin's supervision. Credit:Paul Jeffers After half a decade's research and subjecting 500 volunteers to taste trials Professor Keast proved the human tongue had taste buds that could detect the presence of fatty acids at levels as low as 10 parts per million. "We were using oleic acid that is found in many everyday foods such as olive oil, canola oil, meat and dairy products," he said. Subjects were placed in isolated booths and asked to taste clear cups of water into which was placed tiny amounts of fatty acid. "Around 40 per cent of people detect the fatty acid at very low levels, around 10 parts per million and this figure increases to 80per cent at 100ppm fatty acid."

Professor Keast said the detection of fat by tongue does not give a "conscious perception of taste quality such as sweet or saltiness" instead participants in experiments could detect a different sensation on their tongue. "In high concentrations of fatty acids subjects reported an unpleasant sensation," Professor Keast said. "We (scientists) think that this could be an evolutionary response signalling that the fat in the food may have broken down over time and not be fresh or nutritious." In the paper titled Is Fat the Sixth Taste Primary? Evidence and Implications, Professor Keast outlines ways our ability to taste fat could help treatment of obesity. The paper suggests that people who detect fatty acids also associate the taste sensation with the feeling of being full and that people who have difficulty in detecting fatty acids are often obese. Sensitivity to fatty acids can be increased by putting them on a low fat diet after which their ability to detect fatty acids increases and, by association, their ability to feel full.

The paper also outlines how tasting fat triggers many metabolic processes to aid digestion such as the release of fat digesting enzymes in the digestive system. "These findings could lead to the food industry responding with new products that reintegrate naturally occurring fatty acids to help people feel full," says Professor Keast. "Whether the scientific world accepts fat as a 'taste' like sugar, which gives us a pleasant sensation," he said, "will become a matter of academic debate. But I am positive that we will now see a change in the way we view and perceive fat."