Sugar Alcohols (Polyols) - Sweeteners: Nutritional Aspects, Applications, and Production Technology - page 64

(Bronner 1987; Goda et al. 1993; Kishi et al. 1996), which might be triggered by interactions of the
sugar alcohols with the brush-border membranes (Suzuki et al. 1985; Kishi et al. 1996), the exact
mode of action is unknown. Although intake of large quantities (approximately 20-70 g/day) of
nondigestible saccharides and sugar alcohols causes diarrhea (Ellis and Krantz 1941; Patil et al.
1987), the maximum noneffective dose of maltitol is relatively high, approximately twice that of
sorbitol (Koizumi et al. 1983a,b). Maltitol is thus a potentially useful agent as an enhancer of the
intestinal calcium absorption (Fukahori et al. 1998).
Because maltitol's hygroscopicity and capacity for browning or lavor development differ, the
applications of maltitol correspond largely to those of sugar. Maltitol can be used in the production
of chocolates, hard and soft caramel, toffees, gummy bears, chewing gum, jams, ice cream, etc.
(Fabry and Grenby 1987).

3.4.2 Isomalt

Isomalt, (2R,3R,4R,5R)-6-[ [(2S,3R,4S,5S,6R)-3,4,5-trihydroxy-6-(hydroxymethyl)-2-tetrahydro-
pyranyl]oxy]hexane-1,2,3,4,5-pentol, is a mixture of the diastereomers 6-O-a-d-glucopyranosyl-
d-sorbitol (isomaltitol, 1,6-GPS) and 1-O-a-d-glucopyranosyl-d-mannitol (GPM; the 1-O and
6-O-bound mannitol derivatives are identical because of the symmetry of the mannitol part of the
molecule) obtained by hydrogenating isomaltulose, which is enzymatically derived from sucrose
(Figure 3.13). The two isomers are formed in different ratios, depending on reaction conditions
for the hydrogenation of isomaltulose (Wohlfarth 2006). Indeed, 1,6-GPS is also formed in small
amounts in the catalytic hydrogenation of starch hydrolysates. These isomers belong to the group of
disaccharide alcohols (Schiweck et al. 2011).
With a comparable water content of about 2%, isomalt, in the melt, has a lower viscosity, higher
speciic heat capacity, and higher boiling-point elevation than sucrose (Mende and Schiweck 1991).
The components of isomalt are hydrolyzed by acid to give 1 mol each of glucose and sorbitol or
mannitol. Compared to sucrose and similar disaccharides, the hydrolysis is clearly slower. For this
reason, isomalt can be regarded as acid stable in most food applications. Like those of sucrose, the
hydroxyl groups of the components of isomalt can be etheriied and esteriied (Grillo-Werke 1992).
Isomalt is manufactured in a two-stage process in which sugar is irst transformed into iso-
maltulose, a reducing disaccharide (6-O-α-d-glucopyranosido-d-fructose). The isomaltulose is then
hydrogenated using a Raney nickel catalytic converter. The inal product—isomalt—is an equimo-
lar composition of 6-O-α-d-glucopyranosido-d-sorbitol (1,6-GPS) and 1-O-α-d-glucopyranosido-
d-mannitol-dihydrate (1,1-GPM-dihydrate; Figure 3.14). Now, isomalt has been approved for use in
the United States since 1990. It is also permitted for use in Australia, New Zealand, Norway, Iran,
and the Netherlands (McNutt and Sentko 1996).
Because of its pure sweet taste (sweetening power = 0.45 relative to sucrose in about 10% solu-
tion), its noncariogenicity, and its low caloriic value (0.5-0.6 relative to sucrose), isomalt is almost
the ideal sugar substitute for most applications in confectionery. In the production of foods, isomalt

CH 2 OH
OH

H

CH 2 OH

HO H

O

H H H OH

OH

H

H
O

OH H

HO

H OH

Figure 3.13 Isomalt structure.