See if you know what is inside this basket: one of the items is a miracle fruit, a fruit that is a plant with a berry that, when eaten, causes sour foods such as lemons and limes subsequently consumed to taste sweet. This effect is due to miraculin, which is used commercially as a sugar substitute.

A glycoprotein molecule binds to the tongue’s taste buds, causing sour foods to taste sweet. Miraculin works by binding to sweet receptors on the taste buds. At neutral pH, miraculin binds and blocks the receptors, but at low pH (resulting from ingestion of sour foods) miraculin binds protons and becomes able to activate the sweet receptors, resulting in the perception of sweet taste. This effect lasts until the protein is washed away by saliva up to about 60 minutes.