Wine Chemistry and Biochemistry

7 Carbohydrates 237

CH 2 OH

H OH

HO H

H OH

H OH

CH 2 OH

Glucitol

CH 2 OH

HO H

HO H

H OH

H OH

CH 2 OH

Mannitol

CH 2 OH

O

HO H

H OH

H OH

CH 2 OH

Reduction

Fructose

Fig. 7.8Glucitol and mannitol produced after reduction of fructose

Reducing power of sugars is the basis of a number of classical analytical methods.

Iodine, alkaline ferricyanide and other reagents have been used for analytical pur-

poses.

• Glycoside formation: hemiacetals react with alcohols to form acetals, called gly-

cosides. Acetal formation locks the ring structure, preventing oxidation-reduction

and mutarotation reactions. When acarbonyl group reacts with a hydroxyl group

from other sugar molecule, a disaccharide is created: the formed acetal is sta-

ble and it is called “glycosidic linkage”. Monosaccharides can be polymerized

through glycosidic linkages to form disaccharides, trisaccharides and polysac-

charides.