Polyols, or polyalcohols, are a well-known family of products widely used throughout the world. In the European Union (EU) the family of polyols includes six products; isomalt, lactitol, maltitol, mannitol, sorbitol and xylitol. In the USA these products are described as sugar alcohols chemically defined as saccharide derivatives in which a ketone or aldehyde group is replaced by a hydroxyl group, and whose use is listed by the Food and Drug Administration or is generally recognized as safe.
Numerous fruits contain large amounts of polyols which contribute significantly to their sweetness (Sicard and Le Bot, 1994) (see Table 1). These fruits and vegetables represent the largest proportion of polyols in human consumption. The second source comes from the use of polyols obtained by the hydrogenation of sugars. The main part of this consumption occurs through sugarless, safe for the teeth, and confectionery.
| Polyol | Source of polyol | Content of polyol | |
| D-Sorbitol | Apples | 2.6-9.2 | g D-Sorbitol/l of juice |
| Heaton et al. (1980) | Pears | 11.0-26.4 | g D-Sorbitol/l of juice |
| Cherries | 14.7-21.3 | g D-Sorbitol/l of juice | |
| Sour cherries | 13.1-29.8 | g D-Sorbitol/l of juice | |
| Plums | 1.8-13.5 | g D-Sorbitol/l of juice | |
| Rowan | 85 | g D-Sorbitol/l of juice | |
| (S. aucuparia) | |||
| D-Mannitol | Laminaria spp. | 10% | of dry weight |
| Sicard and Leroy (1983) | Lactarius | 15-20% | of dry weight |
| Agaricus | 15-20% | of dry weight | |
| Xylitol | Yellow plums | 0.93% | of dry weight |
| Washuttl et al. (1973) | Strawberries | 0.36% | of dry weight |
| Cauliflower | 0.30% | of dry weight |
Whereas isomalt is obtained from sucrose and lactitol from lactose, the other polyols can be obtained from sugars derived from starch. A biochemical conversion followed by purification leads to the production of sugars which are then hydrogenated (Le Bot, 1994). In this way glucose leads to sorbitol, fructose to a mixture of mannitol and sorbitol and maltose to maltitol (see Table 6.2).
| Beet or cane | Sucrose | Isomaltulose | α-D-Glucopyranosyl-1.6 sorbitol, α-D-glucopyranosyl-1.6 mannitol, isomalt |
| Corn, wheat | Starch | Maltose, corn syrup, maltose syrup, glucose syrup | Maltitol, maltitol syrup |
| Corn, wheat | Starch | Fructose | Mannitol/sorbitol |
| Corn, wheat | Starch | Glucose, dextrose, glucose syrup | Sorbitol, sorbitol syrup |
| Corn, wheat, birch bark | Starch hemicellulose | Xylose | Xylitol |
Polyols are utilized either because of their sweetness or their technological functional properties. They are bulk sweeteners whose sweetness is generally lower than that of sucrose. Their sweetness is of particular interest since polyols, unlike sugars, do not contribute to dental caries formation. Advantages can also be taken from their reduced energy content (their calorific value is nearly half that of traditional sugars). They can therefore play a part in the formulation of ‘light’ foods. They are useful sugar substitutes providing manufacturers with the means to meet the needs of consumers, eager to enjoy safe and dietetic products whilst not being prepared to compromise on quality.
Beyond their sweetness function, in chocolate and confectionery, for instance, polyols are used for a wide variety of technological reasons in various food applications. They have, for instance, emulsifying, stabilizing, humectancy, thickening and cryoprotecting properties which are advantageous to the food industry.