Miraculin is one of those lovely and bizarre chemicals that fools your nerves (in a tenuously similar way to capsaicin).
Occuring naturally in these little red West African berries, it’s completely tasteless and odourless. What’s amazing about miraculin is that it temporarily fools your tastebuds. After eating some, any sour flavour will taste sweet. So sweet that you could quite happily eat a whole lemon without even wincing. Originally, people considered it to be miraculous, so they named the fruit “Miracle fruit” or “Miracle berries” — hence, miraculin.
Chemically, miraculin is a glycoprotein, and no one knows exactly how it works. It’s thought that it binds to the sweetness receptors in your tastebuds, changing their shape and allowing them to be activated by acidic foods, which are usually sour. The effect lasts around an hour (depending how long it’s in contact with your tongue and how concentrated it is).
This stuff is totally harmless. In fact, it’s legally used as a sweetener in Japan. It has no legal status in Europe and although it was turned down for use as a sweetener in the USA, I don’t think it’s actually illegal there.
Actually, a friend of mine’s buying some from a website. We’re going to buy a load of lemons and raspberries and have a sweet and sour party…