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Synsepalum dulcificum, also known as the miracle fruit, 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. Common names for this species and its berry include miracle fruit,[2] miracle berry, miraculous berry,[2] sweet berry,[3][4][5]

The berry itself has a low sugar content[7] and a mildly sweet tang. It contains a glycoprotein molecule, with some trailing carbohydrate chains, called miraculin.[8][9] When the fleshy part of the fruit is eaten, this molecule binds to the tongue's taste buds, causing sour foods to taste sweet. 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.[10] This effect lasts until the protein is washed away by saliva (up to about 60 minutes).[11]