Chemistry Reference
In-Depth Information
carbohydrates. In certain respects, lactitol is similar to dietary iber. It is also largely metabolized by
the bacterial gut lora (Dills 1989). The clinical beneits of administrating lactitol have been investi-
gated in adults suffering from chronic functional constipation (Ravelli et al. 1995; Vanderdonckt et
al. 1990) and for the management of episodic and acute hepatic encephalopathy in cirrhotic patients
(Lanthier and Mosgan 1985; Scevola et al. 1993; Tarao et al. 1995).
3.4.4 trehalose
Trehalose (α,α-trehalose; α-d-glucopyranosyl-(1→1)-α-d-glucopyranoside) is a disaccharide
composed of two glucose molecules bound by an alpha, alpha-1, 1 linkage (Figure 3.17). The bond-
ing makes trehalose very resistant to acid hydrolysis and therefore is stable in solution at high tem-
peratures, even under acidic conditions. The bonding also keeps nonreducing sugars in closed-ring
form, such that the aldehyde or ketone end groups do not bind to the lysine or arginine residues of
proteins (a process called glycation). Trehalose is broken down by the enzyme trehalase into glucose
and has about 45% the sweetness of sucrose. It is less soluble than sucrose, except at high tempera-
tures (>80°C). Trehalose forms a rhomboid crystal as the dihydrate and has 90% of the caloriic
content of sucrose in that form. Anhydrous forms of trehalose readily regain moisture to form the
dihydrate and can show interesting physical properties when heat-treated (Higashiyama 2002).
Trehalose was previously being manufactured through an extraction process from cultured
yeast, but, since production costs were prohibitive, use was limited to only certain cosmetics and
chemicals. In 1994, Hayashibara, a sacchariied starch maker in Okayama prefecture, Japan, dis-
covered a method of inexpensively mass-producing trehalose from starch (Hayashibara 1994). The
following year, Hayashibara started manufacturing trehalose by activating two enzymes, the gluco-
syltrehalose-producing enzyme that changes the reducing terminal of starch into a trehalose struc-
ture and the trehalose free enzyme that detaches this trehalose structure. As a result, a high-purity
trehalose from starch can be mass-produced for a very low price (Higashiyama 2002).
Since the reducing end of a glucosyl residue is connected with the other, trehalose has no reduc-
ing power. Trehalose is widely distributed in nature. It is known to be one of the sources of energy in
most living organisms and can be found in many organisms including bacteria, fungi, insects, plants,
and invertebrates. Mushrooms contain up to 10%-25% trehalose by dry weight. Furthermore, tre-
halose protects organisms against various stresses such as dryness, freezing, and osmopressure. In
the case of resurrection plants, which can live in a dry state, when the water dries up, the plants also
dry up. However, they can successfully revive when placed in water. The anhydrobiotic organisms
are able to tolerate the lack of water owing to their ability to synthesize large quantities of trehalose,
and the trehalose plays a key role in stabilizing membranes and other macromolecular assemblies
under extreme environmental conditions (Higashiyama 2002).
Trehalose's relative sweetness level is 45% of sucrose. Trehalose has high thermostability and a
wide pH-stability range. Therefore, it is one of the most stable saccharides. When 4% trehalose solu-
tions with pH 3.5-10 were heated at 100°C for 24 h, no degradation of trehalose was observed in any
CH
2
OH
O
CH
2
OH
OH
O
O
HO
OH
OH
OH
OH
Figure 3.17
Structure of trehalose.
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