The Miracle Fruit plant (Synsepalum dulcificum) produces berries that, when eaten, cause bitter and sour foods (such as lemons and limes) consumed later to taste sweet... Miracle fruit is available as freeze dried granules or in tablets - this form has a longer shelf life than fresh fruit. Tablets are made from compressed freeze dried fruit which causes the texture to be clearly visible even in tablet form. The effect of Miracle fruit is made possible by contact with the tongue, not through digestion. For this reason, tablets must be allowed to dissolve in the mouth.
My son just gave me a miracle fruit tablet which I dissolved in my mouth, and I am now chewing a slice of raw lemon and it tastes like lemon sugar, or a lemon sweet. I am not exaggerating in the slightest. It's almost so sweet that I don't like it. 'Miraculin' temporarily bonds to the sweet receptors of the tongue, so they react to sour and bitter flavours as if they are sweet. The acidity of the lemon is slightly irritating my throat, but I am quite unaware of any sour taste.
The berry contains an active glycoprotein molecule, with some trailing carbohydrate chains, called miraculin... this molecule binds to the tongue's taste buds... This effect lasts between thirty minutes and two hours.
Personally, I don't like super-sweet flavour too much, so I probably won't do it again, but it's a strange almost hallucinogenic experience. It is used medically to help people with diabetes and undergoing chemo.