Monday, October 12, 2015

Discovery Central & ChEmIcAmAzInG - The Freezing Taste of Menthol

Menthol formula
Eating a peppermint or a slice of mint cake, especially during a hot day,  is such a pleasurable experience. Feeling that fantastic sense of cold is one of the reasons we love these sweets so much. And obviously the characteristic flavor is loved everywhere. But why mint tastes cold? is temperature really involved in this process or maybe is just a trick of our body? Let’s find out…

Menthol Crystals
Most of you knows that the responsible is Menthol, an organic compound normally obtained from all mint plants. Of course nowadays, with the extreme high demand and the huge amount of products is used in, menthol is synthetically produced in form of a waxy, crystalline substance that can be both clear or white. At room temperature is solid, but few degrees are enough to make it melt.

What happens when we eat a product that contains menthol? Well, our mouth contains some specific receptors that responds to this chemical compound. The receptor we’re talking about, which in this case is a protein called TRPM8 (the actual name is Transient Receptor Potential Cation Channel, Subfamily M, Member 8) tricks the brain into thinking that the area the menthol is applied to is cold. The truth is that there’s no actual change in temperature.

But if there’s no changing in temperature, why do we sense cold? The scientific explanation of  the process is the perfect answer. The protein TRPM8 is a “ion channel”, so you can easily imagine it as a sort of bridge for ions. When this bridge is open, it allows sodium and calcium ions to enter, causing an electrical signal down a neuron called  Action Potential. This is what happens when menthol is detected by the receptor.

Here comes the trick. In fact TRPM8 is also a temperature receptor that opens in response to low temperatures. When menthol’s around (to be specific a mix of Menthol and Menthone, another molecule strictly similar to menthol and vastly used in cosmetics), the TRPM8 channel opens, but this signal “hey, there’s menthol” is indistinguishable from the signal “I’m freezing in here”. The result is a mixed signal that triggers the brain and so, when it detects menthol, the receptor also signals cold, making mint feel cold even though temperature never changed.

So Menthol makes TRPM8  much more sensitive than normal and this is verified every time you breathe in deeply through your mouth after eating a peppermint. By introducing air inside, your cold receptors are reacting much more strongly than they normally would to the air. What you can physically feel is an extra freezing sensation. But the air is not cold at all.

But Confectionery Industry is just one of the lots of uses Menthol has. Mint leaves or mint oil containing high levels of menthol help repel and kill mosquitoes. Menthol is also very effective against muscle aches and pains and throat irritations (and this is why sometimes menthol is added in cigarettes), and the cooling sensation it provides is helpful to treat sunburns. And last but not least, menthol crystals can be used as an ice substitute for drinks.
A little encourage mint for you <3

You didn’t expect this pleasurable sensation was caused by menthol cheating on your brain, did you?

And now a little experiment for “The Fair of Molecular Cheaters” with Menthol and Capsaicin (if you haven’t read the article The Burning Taste of Capsaicin go check it out): Take a pepper, a peppermint and eat them at the same time. Capsaicin and Menthol have the same effects on the receptors (more or less), but who tried it felt a particular, unique sensation. Come on, try it for science. And Never Stop Snooping Around. 


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