An aftertaste can make the difference between a great wine and a terrible one. Likewise, the bitter aftertaste of coffee turns some people off the stuff. The reason for aftertaste – the perception of taste after the food has been removed from the mouth – is somewhat mysterious…
The science of aftertaste
If you zoom in on the taste buds of the tongue, you will see clusters of taste receptor cells. These sensitive cells have tiny hair-like projections (called microvilli) on their surface, which are designed to sense specific chemicals in food. Such chemicals we perceive as a taste; for example, sugar-molecules are sensed as ‘sweet’.
Now, if you zoom in even further on the taste receptor cell, on the surface of the microvilli are molecular receptors – carefully shaped to the chemicals we can taste (e.g. sugar). There are different types of molecular receptors shaped for different taste chemicals (sweet, bitter). When a specific taste molecule comes into contact with its molecular receptor (it slots in, like a key into a lock) , a chain reaction is triggered within the cell. These chemical reactions within te cell in turn sets off a nerve impulse to the brain. (‘ooh, that tastes nice!’)
Ordinarily, these molecular receptors are only activated when a ‘taste chemical’ comes into contact with it. When you swallow the food, it is washed off. However, certain chemicals (e.g. those which cause a bitter aftertaste) are believed to activate the taste receptor cell by bypassing these molecular receptors. Rather than just sitting on the cell’s surface aftertaste-causing substances seep into the cell itself. Once diffused into the taste receptor cell’s inside, these ‘after-taste’ substances linger – triggering a prolonged taste sensationeven after the food has been swallowed.
Eventually, the aftertaste molecule is broken down from within the cell’s interior and the aftertaste subsides. And as you know, this can happen quickly or slowly depending on what you’ve eaten.
How to get rid of after-taste
Sadly, after-taste is an intrinsic property of many foods. To avoid it, you have to not put it into your mouth. Drinking milk can have a soothing effect, as can eating cucumber, but won’t get rid of it. Once those after-taste-inducing substances have come into contact with the tongue, they will have passed into the taste receptor cells. At which point you can’t get them out again. You just need to wait.
This hasn’t stopped food scientists developing ingenious ways of getting rid of after-taste from foods. A ‘fishy’ aftertaste in certain wines is believed to be caused by iron; and one new technique treats the wine with yeast to remove iron. Huge amounts of money are poured into reducing the bitter aftertaste of artificial sweeteners, and given their widespread use, discovering a solution would yield vast financial dividends for the discoverer. Essentially, all techniques for removing aftertaste from foodstuffs involve treating it, or altering its manufacturing process first. Most of these processes haven’t made it onto the shop-floor yet, so for now you’ll have to avoid whatever causes an unpleasant aftertaste. Shame.
Asked by Julio Vazquez via Facebook
Answered by Dr Stu
Some high-level reading for the academics here about taste receptor cells