Why Are Sweeteners Bitter?

From diet soft drinks to low calorie lattes, the artificial sweetener movement has gained huge momentum over the past decade.  Saccharin and cyclamate are two of the most popular sweeteners on the market, working together to tantalise the tastebuds. But interestingly, when used alone they can have a bitter aftertaste.

Finding a balance

Why? It's all about creating a balance. When used solo, saccharin and cyclamate trigger both sweet and bitter sensations. But when combined each sweetener cancels out the other's bitterness. The result is a perfectly sweet sensation, without the tart aftertaste.

So how does it work? The human tongue is covered in tiny molecules that act as receptors. They detect certain chemicals and allow the tastebuds to detect sweet, salty, sour, bitter and savory sensations. Artificial sweeteners work by using a chemical structure to activate the tongue's sweet receptors. They do a great job, with cyclamate is 30 to 40 times sweeter than sugar and saccharin around 300 times more powerful.

A "bitter sweet" reaction

That said, they're not perfect. While the primary sensation is sweet, saccharin and cyclamate can also trigger the tongue's bitter receptors which creates an unpleasant aftertaste. In the 1950s scientists realised that combining the two helped to mitigate this unwanted aftereffect. However, until now the specifics of why the solution worked were unknown.

Now, German molecular biologist Maik Behrens and his colleagues have gained new insight. Working from the German Institute of Human Nutrition, the team are on a mission to pinpoint exactly which bitter taste receptors are triggered by saccharin and cyclamate. They've spent months analysing the genes of all 25 of the tongue's known bitter receptors and come up with some exciting results.

Clogging the tastebuds

While cyclamate activates two bitter receptors, it also blocks different bitter receptors that are triggered by saccharin. It does this by slipping into the tiny spaces and clogging the receptors. Saccharin works in a similar way by blocking the bitter that cyclamate activates.

The findings were reported in the journal Cell Chemical Biology, with brain scientist Yuki Oka explaining, “This addresses a longstanding puzzle: why mixing two different sweeteners changes the aftertaste. They are interrupting each other at the receptor level.”

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