Sugar Alcohols (Polyols) - Sweeteners: Nutritional Aspects, Applications, and Production Technology - page 59

granulation (Schmidt and Benke 1985). This type of sorbitol is also suited to the production of
stable dry suspensions (e.g., with antibiotics) of vitamin tablets or antacid granules (Nikolakakis and
Newton 1989). Sorbitol syrup is important primarily as a moisture stabilizer and softener. About
25% of the worldwide production of sorbitol is used for this purpose (Schiweck et al. 2011).
3.3.4 Mannitol
Mannitol, (2 R ,3 R ,4 R ,5 R )-hexane-1,2,3,4,5,6-hexol, is the alcohol form of mannose with a
molecular weight of 182, prepared commercially by the reduction of dextrose (Figure 3.9a). It
is sparingly soluble in many organic solvents such as ethanol (1.2 g/100 mL) and glycerol (5.5
g/100 mL), and practically insoluble in ether, ketones, and hydrocarbons. Mannitol has an mp of
165°C-168°C and relative density of d 20 = 1.52; the particle-size distribution of crystalline grades
is 20-250 μm and that of granulated grades is 100-850 mm; its bulk density is 550-650 g/L. The
viscosities of mannitol and sorbitol solutions are comparable. Crystalline mannitol is only slightly
hygroscopic; appreciable water absorption occurs at >90% relative humidity. Mannitol, like other
hexitols, forms chelate complexes with metal ions (e.g., iron, copper, and nickel) in aqueous solu-
tion. The iron complexes are especially stable. Even at 150°C-170°C, mannitol does not react with
proteins according to the Maillard reaction. Nitration of mannitol with nitrating acid yields man-
nitol hexanitrate (hexanitromannitol), which is used as an igniter for detonators and electrical fuses.
Although it has an important place in current therapy, few physicians fully understand its chemistry,
mode of action, or clinical applicability. Of the commercially used sugar alcohols, mannitol is the
least soluble in water. Because of its positive heat of solution in water, a cooling sensation occurs
when mannitol dissolves in the mouth. This effect is, however, less pronounced than that observed
with sorbitol or xylitol (Grenby 1989; Schiweck et al. 2011; Ziesenitz and Siebert 1987).
d-Mannitol is widespread in nature. It is found to be a signiicant extent in the exudates of trees
and shrubs such as the plane tree (80%-90%), manna ash (30%-50%), and olive tree. Mannitol
occurs in the fruits, leaves, and other parts of various plants. This hexitol is present in pumpkins,
hedge parsley, onions, celery, strawberries, the genus Euonymus , the genus Hebe , the cocoa bean,
grasses, lilac, Digitalis purpurea , mistletoe, and lichens. Mannitol also occurs in marine algae,
especially brown seaweed, with a seasonal variation in mannitol content that can reach over 20%
in the summer and autumn (Kearsley and Deis 2006; Song and Vieille 2009). It is extracted from
seaweed for use in food manufacturing and is sometimes used as a sweetener in dietetic products.
Mannitol is found in the mycelia of many fungi and is present in the fresh mushroom to the extent of
about 1.0% (Kearsley and Deis 2006). It was reported that there is a direct relation between mush-
room yield and mannitol content (Kulkarni 1990).
Mannitol is commonly used as a nutritive sweetener, stabilizer, humectant, and bulking agent in
foods and supplements. This sugar alcohol is approximately 0.7 times as sweet as sucrose. It is used
as a bulking agent in powdered foods and as a dusting agent for chewing gum. It can be derived from
the Manna plant or from seaweed; however, for commercial use, it is manufactured via a catalytic
hydrogenation process (Schiweck et al. 2011).
The chemical structure of mannitol allows it to be absorbed more slowly by the body than
regular sugars. Therefore, it has a smaller impact on blood insulin levels, making it and other sugar
alcohols useful for diabetic foods. Mannitol is not absorbed in the GI tract; moreover, it does not
cross an intact blood-brain barrier (BBB). It does not enter cells and is cleared by glomerular iltra-
tion. The glomeruli ilter mannitol, which does not get reabsorbed from renal tubules; therefore,
mannitol increases the osmolarity of renal tubular luid and prevents reabsorption of water. Sodium,
the renal tubular luid, is diluted and less is reabsorbed. Mannitol works osmotically to create diure-
sis. It works by creating an osmotic gradient. Side effects result from its osmotic effect. It increases
intravascular volume, which can precipitate pulmonary edema and/or congestive heart failure,
especially in patients with poor cardiac function. Hypovolemia can occur along with hypotension.