Published in Chemical Senses, the research outlines exactly how humans use the nose and tongue to recognise the flavour of foods. Led by Juyun Lim from Oregon State University, USA, the researchers note that humans are ‘wired’ to prefer sweet-tasting and avoid bitter-tasting foods as an evolutionary survival mechanism which in the past had helped humans to avoid poisonous foods and find foods that provided energy.
Now, however, such preferences “just makes us fat,” say the researchers.
“There has been confusion for centuries about exactly how our senses of taste and smell work. We’re finally starting to work this out,” said Lim, who noted that there are actually several senses that relate to the perceived ‘flavour’ of a food.
These include taste, which resides solely in the tongue; smell, which is exclusively in the nose; and somesthesis, which includes things like touch, temperature, and the burn of hot peppers.
In the new study, Lim and her colleagues reveal that when odour and taste components of foods are congruent they are perceived as one sensation which seems to come from the mouth, but when they are not people believe they are smelling certain attributes.
“This is a trick that the brain plays on us,” said Lim. “Vanilla has no taste at all. It’s a smell, and the pleasant sensation is coming not from your mouth but from the nose, through the passage way between the back of the mouth and the back of the nose.”
She noted that when the vanilla aroma is matched with a congruent mouth flavour – such as sugar – the entire sensation seems to come from the mouth. But when the mouth flavour is incongruent and not as commonly found together – for example vanilla and salt – people believe they are smelling the vanilla from the nose rather than tasting it in the mouth.
“This was an amazing part of our experiments, we did not expect a result so compelling,” revealed Lim, who noted that even though the mouth and nose are closely connected – such tastes and smells do not actually interact with each other.
Lim concludes that flavour perception is still largely a learned behaviour. And if it’s learned, she argues, humans should be able to teach it better, or at least find ways to work around such evolutionary instincts.
“Hardly anyone really likes the somewhat bitter taste of coffee the first time they drink it, but they like the caffeine,” said Lim. “Since the coffee makes them feel energised, they learn to like its flavour.”
She suggests that as the understanding of how taste and smell actually work to control our perceptions of flavour improve, it may be possible to use that knowledge to help improve diets.
“Many people say they don’t like the ‘taste’ of cruciferous vegetables like cauliflower or brussel sprouts, for instance,” Lim said. “But what they are mainly reacting to is the smell of these vegetables, which includes a defensive compound that makes even other animals shy away from eating them. Find a way to help improve their smell, and you’ll find a way to make people enjoy eating them.”
Her team is currently investigating whether people can learn to like vegetables, and the potential mechanisms underlying that process.