Miracle berry's sweet secret
If you could miraculously make bitter food turn sweet, would you do it? Dr Karl reveals the secret to the amazing taste trick of miracle fruit.
Last time, I talked about a small red fruit or berry from tropical west Africa, which goes under the fairly accurate name of miracle fruit or miracle berry.
It has a very strange property. If you eat miracle fruit and then consume something acid or bitter, such as lemons or vinegar, almost miraculously all you taste is sweetness.
Let me tell you how miracle fruit turns sour into sweet.
The active ingredient in miracle fruit is a mid-size chemical called miraculin. It has a molecular weight of about 25,000 Daltons, which is about five-times heavier than insulin, or 1400 times heavier than water.
This chemical lands on your tongue. Your tongue has the sense of taste because it's covered with a few thousand taste buds.
Each taste bud holds about 50–100 taste receptor cells. Each of these taste receptor cells will respond to only one of the five basic tastes: sweet, salt, sour, bitter and umami.
So, for example, when a sweet-tasting chemical lands on a taste receptor cell that responds specifically to sweetness, then that cell gets activated and sends a signal to the brain.
To understand the secret of miracle fruit, we need to go into a bit more detail.
Most chemicals talk or interact with your cells via their shape. It's a lock-and-key kind-of thing. In your front door, if the key is the exact correct shape for your lock, then the lock opens and you can get into your house.
In the same way all cells in your body, including the hundreds of thousands of taste receptor cells on your tongue, are covered with microscopic receptors. They're like tiny locks.
These receptors are hollow. If a chemical can fit into that receptor, and make a good fit, then the cell will do something.
In the case of taste receptor cells, that 'something' is to tell your brain that you have just tasted one of the five basic tastes.
Now here's the trick of miracle fruit.
The active ingredient, miraculin, is a pretty bad fit into the sweet receptor under normal conditions. But it is a darn good fit under acid conditions!
Normal conditions are that you eat miracle fruit and the chemical called miraculin slots into the sweet receptors on your tongue. But it's a very sloppy and loose fit.
Remember the example of your key fitting into the front door lock? If it doesn't fit exactly, it doesn't work. So the miraculin does not send the impression of sweetness to your brain, even though it has slotted into the receptor (or lock).
In fact, if you eat something sweet, your brain won't know, because the miraculin is already sitting there in all of the sweetness receptors and it stops the sweet food you have just eaten from getting into those receptors.
Then you eat or drink something acid.
The miraculin suddenly changes shape so that it is now a good fit inside the receptor. In fact, it's better than just a good fit, it's an almost perfect fit.
How perfect? A lot better than sugar. In fact, 100-million-times better, and a million-times better than the artificial sweetener, aspartame.
So your brain is being told that there's a lot of sweetness on your tongue even though you are eating a very sour lemon.
Under these acid conditions the miraculin also makes the sweetness receptors extra sensitive. So they will respond extra strongly to a sweetener like aspartame.
The miraculin chemical will hang in there inside your sweet receptors on your tongue for over an hour before it leaves.
Scientists are using genetic engineering to modify other plants, such as fruits or vegetables, to grow the active ingredient, miraculin.
So this natural product could be used, say, for diabetics to satisfy their sweet tooth without the extra calories or kilojoules that sweetness normally brings.
But, as the great physicist, Richard Feynman said, "you can't fool nature".
Sure, you've had a wonderful party going off in your mouth as you gobbled down lemons, vinegar, pickles and beer, glorying in the strange new taste sensations from your easily fooled brain.
But your stomach is not fooled. It's full of lemons, vinegar and all kinds of other food items that your taste buds would normally warn you should not be mixed.
Get ready for the mother of all tummy aches.
Published 11 October 2011
© 2014 Karl S. Kruszelnicki Pty Ltd