c) Polyols (alditols)
- Both aldoses and ketoses are reduced to polyhydric alcohols (polyols) when treated with enzymes, sodium amalgam, and hydrogen under high pressure with catalyst or sodium borohydride. Each aldose yields the corresponding alcohol upon reduction. A ketose forms two alcohols because of the appearance of a new asymmetric carbon atom in the process.
By this reduction process, the following sugars give rise to their respective alcohols under specified conditions.
| Glucose
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Sorbitol
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| Fructose
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Sorbitol and mannitol
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| Mannose
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Mannitol
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| Glyceraldehyde
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Glycerol
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| Erythrose
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Erythritol
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| Ribose
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Ribitol
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| Galactose
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Dulcitol
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- Polyols occur in many plant products.Sorbitol was first isolated from the berries of mountain ash (Sorbus aucuparia).Commercially sorbitol is manufactured by the hydrogenation of glucose.Mannitol occurs in many terrestrial and marine plants.Potential food applications of polyols include confectionery products, bakery products, deserts, jams and marmalade.Sorbitol is an excellent moisture conditioner and is used in pharmaceutical preparations such as elixirs and syrups. Sorbitol, as a humectant in creams and lotions helps to stabilize the water content, providing better moisture control. The use of sorbitol or xylitol in toothpaste and mouthwashes is highly desirable.
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Last modified: Tuesday, 27 March 2012, 6:35 PM
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