Mannitol comes in white crystalline powder form or in diluted solutions. It is naturally occurring in many organisms like plants, fungi, bacteria and more. Traditionally, mannitol was extracted from plants like seaweed since it was present in abundance. Today, it can be produced industrially through hydrogenation of fructose. Due to its low toxicity and health benefits, mannitol is listed by the World Health Organisation as one of the world’s most effective and safe medicines needed in a health system.
Mannitol can be produced through hydrogenation of fructose.
Raney copper catalyst, prepared from cooper/aluminium alloy, is used in this process. High purity fructose (95-100%) is hydrogenated in a continuous fixed bed process in a hydrogenator reactor. In the hydrogenator reactor, the catalyst used is Raney copper catalyst, made from copper/aluminium alloy. This process is carried out under hydrogen pressure of 160-200 bar and in pH 4.0-6.0 for optimal yield of mannitol. It is then filtered hot to remove impurities and crystallized to form mannitol powder.
Naturally, mannitol can be synthesised via fermentation of fructose in organisms. These are then extracted manually.
In medicines, mannitol is used to decrease intercranial pressure. It is also used in acute kidney failure to boost urine output so toxins can be flushed out and to decrease eye pressure. In children, mannitol is also used as an osmotic laxative to promote bowel movements. Mannitol regulates renal functions in patients when they are on bypass.
In food, mannitol has a lower glycemic index than most sugar. Thus, it is suitable to be used as sweeteners for diabetic patients. When mannitol is completely dissolved in water, it induces a strong cooling effect and are often used in mint flavoured candies and gums. Due to its low hygroscopicity, it is suitable to be used as coating of candies, dried fruits and chewing gum.
In laboratory, mannitol is often used with boric acid to increase the acid strength of boric acid so it can be measured with higher precision.