Mannitol is also called D-mannitol. Molecular formula is C6H14O6. Molecular weight is 182.17 . It is a familiar hexahydric alcohol and the isomer of sorbitol. It is a kind of nonhygroscopic, smell-less, colorless crystalline powder. Density is 1.489 . Melting point is 166~168℃. Boiling point is 290~295℃(0.4~0.467kPa). Optical rotation is +23~+24°.

Mannitol has happy sweetness. The sweetening power is 55-65% of cane sugar. It has the common character of polyol and firstly it was found in plant of pumpkin, mushroom, onion and seaweed. Mannitol widely exist in seaweed, some fruits and trees in the nature. The white powder on surface of dried persimmon which have good function of relieving a cough is mannitol. Kelp content 10-20% mannitol. The white powder on surface of dried kelp is compound of mannitol and bittern. Fresh mushroom content about 1% mannitol. So mannitol is the first functional polyol that enter human lives in social development history.

Mannitol is the only nonhygroscopic hexahydric alcohol in all polyol and it have bland sweetness, low colaric and nontoxic. In human body metabolism it is same with other polyol and don't rely on insulin, don't enhance blood sugar, don't cause delayed tooth, etc. So it can be used as sweetener for diabetic and human of adiposis.

At present we can supply two kinds of technological process to produce mannitol. One is using materials of seaweed to produce alginate while concentrate , remove impurity, ion exchange, evaporate and concentrate, cool and crystal the mother liquor which had been extracted iodine. The another technologic process is hydrolyze raw materials of cane sugar and dextrose, and then epimerized and isomerized , add hydrogen finally to produce mannitol.