Scientists have claimed to have solved the mystery of why coffee never tastes as good as it smells.

Apparently, the act of swallowing the drink sends a burst of aroma up the back of the nose from inside the mouth, activating a “second sense of smell” in the brain that is less receptive to the flavour, causing a completely different and less satisfying sensation.

“We have got two senses of smell. One sense is when you inhale things from the environment into you, and the other is when the air comes out of you up the nasal passage and is breathed out through the nose,” the Telegraph quoted Prof Barry Smith, of the University of London, as saying at the British Science Festival in Aberdeen.

The phenomenon is down to the fact that, although we have sensors on our tongue, 80 percent of what we think of as taste actually reaches us through smell receptors in our nose, the paper said. The receptors, which relay messages to our brain, react to odours differently depending on which direction they are moving in, it added.

In the case of coffee, the taste is also hampered by the fact that 300 of the 631 chemicals that combine to form its complex aroma are wiped out by saliva, causing the flavour to change before we swallow it, Prof Smith added.