Chemistry Reference
In-Depth Information
frequently present in plant exudates (Lohmar 1962). Erythritol exists in both fruits (Shindou et al.
1989) and mushrooms (Yoshida et al. 1986), but the amounts in these products are extremely low.
Sorbitol (Winegrad et al. 1972), d-mannitol (Laker and Gunn 1979), and xylitol are also endogenous
metabolites in mammals.
Polyols are important sugar substitutes and are utilized in different food formulations for their
different sensory, special dietary, and functional properties, which make them feasible. Thus, poly-
ols are used in low-calorie food formulations in different countries including the United States
and in most European countries. Since they are absorbed more slowly in the digestive tract than
sucrose, they are useful in certain special diets. However, if consumed in large quantities, some of
them can have a laxative effect. Polyols offer the same preservative beneit and a similar bodying
effect to food as sucrose. They are more resistant to either thermal breakdown or hydrolysis than
sugar. Moreover, most polyols are resistant to fermentation by oral bacteria and are therefore prime
ingredients for tooth-friendly confectionaries such as sugarless or sugar-free chewing gums (Wang
2003; Ziesenitz and Siebert 1987).
Exogenous polyols are absorbed slowly, and metabolism mechanism in the liver mainly includes
conversion to the corresponding 2-keto sugars by the action of nonspeciic NAD-dependent polyol
dehydrogenase (McCorkindale and Edson 1954). Unlike xylitol, sorbitol, and d-mannitol, erythritol
is not a precursor of liver glycogen (Mäkinen 1994). Xylitol and sorbitol are metabolized com-
pletely after moderate administration, whereas d-mannitol is poorly utilized due to its low afinity
for l-iditol dehydrogenase, causing an increased d-mannitol concentration in urine (Dills 1989).
Exogenous erythritol is very poorly metabolized, being excreted almost completely in urine without
degradation (Noda et al. 1994).
Polyols are also used in the diets of diabetic subjects and in infusion therapy solutions as ingre-
dients. Compared to xylitol and sucrose, which are approximately of equal sweetness (Moskowitz
1971), d-mannitol is 45%-57% (Moskowitz 1974), erythritol is 75%-80% (Kawanabe et al. 1992),
and sorbitol is 35%-60% (Wright 1974) as sweet at equal weight. Like xylitol, sorbitol has an energy
value similar to that of sucrose. d-Mannitol, when consumed as part of a mixed diet, has a reduced
energy value (Dills 1989). Erythritol is a very low-energy sweetener, with the available energy
value being under 10% of that of sucrose (Noda and Oku 1992; Table 3.3). Other polyols share
some properties with xylitol, also with regard their association with calcium metabolism. Sorbitol
and d-mannitol increase calcium absorption and urinary calcium excretion in rats (Hämäläinen
and Mäkinen 1986; Knuuttila et al. 1989; Vaughan and Filer 1960). Dietary sorbitol also increases
the concentration of bone calcium, although less than xylitol (Knuuttila et al. 1989). Absorption,
fermentation, and urinary secretion of polyols are different from each other (Table 3.4). Therefore,
depending upon these properties, they are used in different formulas.
3.3 MONOSaCCharIDe pOLYOLS
3.3.1 erythritol
Erythritol ((2R,3S)-butane-1,2,3,4-tetraol) is an acyclic carbohydrate consisting of four carbon
atoms, each carrying a hydroxyl group (Figure 3.3). Since it exhibits a meso structure, the molecule
is achiral, although exhibiting two asymmetric carbon atoms (2R and 3S). Therefore, the molecule
does not have optical rotation (Schiweck et al. 2011).
Erythritol has been approved for use as a food additive in the United States (Kawanabe et
al. 1992) and throughout much of the world. It was discovered in 1848 by British chemist John
Stenhouse and was commercialized during the 1990s in the Japanese market. It was the irst polyol
to be industrially produced by a fermentation process (Schiweck et al. 2011). It has a clean sweet
taste that is similar to sucrose, and it is an anhydrous, nonhygroscopic white crystalline powder
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