Miracle Berry turns sour into sweet!

How miraculin, a protein found in the African "Miracle Berry", fools the tongue into experiencing sour foods like lemons as sweet, and sweet things to be tasteless, has been revealed by reserachers in Japan.

Writing in Seminars in Cell & Developmental Biology, the University of Tokyo team discovered that, under acidic conditions like those experienced when sucking a slice of lemon, miraculin can activate sweet-sensing taste buds on the tongue. This can make low-sugar foods taste sweeter, raising the possibility of using miraculin to combat conditions like obesity and diabetes.

The Miracle Berry, or Richadella dulcifica is the fruit of a shrub native to West Africa. Historically, locals have used it to improve the taste of sour palm wine or fermented bread. However the way in which it works has, until recently, remained unknown.

Now, thanks to the recent discovery of a sweet-sensing taste receptor on the tongue, called hT1R2-hT1R3, the Tokyo team have been able to unpick the way in which miraculin affects our sense of taste.

The hT1R2-hT1R3 sweet receptors were added to the surfaces of cells grown in a laboratory dish alongside a dose of miraculin and a fluorescent indicator to make the cells to light up whenever the sweet-sensing taste receptors were activated.

Surprisingly, miraculin didn't trigger the cells to light up as much as expected when sweet substances were administered, suggesting that incubation with miraculin actually had a dampening effect on the cells' responses.

However, adding acidic subtances (like those found in lemons, which usually activate our sour taste receptors) caused the cells to light up strongly. This showed that acids activate the miraculin-bound cells. The effect also strengthened as the acidity increased. Substances which were neither acidic nor alkaline showed no significant activation of the cells. This explains why eating the Miracle Berry causes us to experience sweet foods as tasteless, but sour foods taste sweet.

As well as having great potential in combating lifestyle conditions such as obesity and diabetes, these new findings mean that miraculin can also be used as a taste enhancer for patients undergoing chemotherapy, which has been known to leave a foul taste in the mouth and impact on patient's nutrition.

Potentially even more exciting are the recreational possibilities - it may be possible to use this newly-understood effect to create a host of new tastes and flavours from what might previously have been regarded as bland and boring foods...