What are polyols?

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.

PolyolSource of polyolContent of polyol
D-SorbitolApples2.6-9.2g D-Sorbitol/l of juice
Heaton et al. (1980)Pears11.0-26.4g D-Sorbitol/l of juice
Cherries14.7-21.3g D-Sorbitol/l of juice
Sour cherries13.1-29.8g D-Sorbitol/l of juice
Plums1.8-13.5g D-Sorbitol/l of juice
Rowan85g D-Sorbitol/l of juice
(S. aucuparia)
D-MannitolLaminaria spp.10%of dry weight
Sicard and Leroy (1983)Lactarius15-20%of dry weight
Agaricus15-20%of dry weight
XylitolYellow plums0.93%of dry weight
Washuttl et al. (1973)Strawberries0.36%of dry weight
Cauliflower0.30%of dry weight
Table 1. Natural occurrence of polyols

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 caneSucroseIsomaltuloseα-D-Glucopyranosyl-1.6 sorbitol, α-D-glucopyranosyl-1.6 mannitol, isomalt
Corn, wheatStarchMaltose, corn syrup, maltose syrup, glucose syrupMaltitol, maltitol syrup
Corn, wheatStarchFructoseMannitol/sorbitol
Corn, wheatStarchGlucose, dextrose, glucose syrupSorbitol, sorbitol syrup
Corn, wheat, birch barkStarch hemicelluloseXyloseXylitol
Table 2. Origins of polyols

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.

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