Sugar alcohols: chemistry, production, health concerns and nutritional importance of mannitol, sorbitol, xylitol, and erythritol

Abstract

The sugar alcohols commonly found in foods are sorbitol, mannitol, xylitol, erythritol, isomalt, and hydrogenated starch hydrolysates. Sugar alcohols come from plant products such as fruits and berries. Sugar alcohols occur naturally and at one time, mannitol was obtained from natural sources. Today, they are often obtained by hydrogenation of sugars and other techniques. Sugar alcohols do not contribute to tooth decay. Consumption of sugar alcohols may affect blood sugar levels, although less than of sucrose. Sugar alcohols, with the exception of erythritol, may also cause bloating and diarrhea when consumed in excessive amounts. Mannitol and sorbitol are isomers, the only difference being the orientation of the hydroxyl group on carbon 2. Among production methods of mannitol are Industrial synthesis, Biosyntheses, Natural extraction, chemical process, microbial process. Most sorbitol is made from corn syrup, but it is also found in apples, pears, peaches, and prunes. It is converted to fructose by sorbitol-6-phosphate 2-dehydrogenase. Xylitol is a "tooth-friendly", nonfermentable sugar alcohol. It appears to have more dental health benefits than other polyalcohols. The structure of xylitol contains a tridentate ligand, (H-C-OH)3 that can rearrange with polyvalent cations like Ca2+. This interaction allows Ca2+ to be transported through the gut wall barrier and through. Xylitol is produced by hydrogenation of xylose, which converts the sugar (an aldehyde) into a primary alcohol. Another method of producing xylitol is through microbial processes, including fermentative and biocatalytic processes in bacteria, fungi, and yeast cells, which take advantage of the xylose-intermediate fermentations to produce high yield of xylitol. In the body, most erythritol is absorbed into the bloodstream in the small intestine, and then for the most part excreted unchanged in the urine. About 10% enters the colon. Because 90% of erythritol is absorbed before it enters the large intestine, it does not normally cause laxative effects. Chemical and fermentative processes have been introduced for large-scale production of erythritol. Erythritol can be synthesized from dialdehyde starch by high-temperature chemical reaction in the presence of a nickel catalyst.