234 M. Luz Sanz and Isabel Mart ́ınez-Castro
CHO
HO H
H OH
H OH
CH 2 OH
CHO
H OH
HO H
HO H
CH 2 OH
D-arabinose L-arabinose
Fig. 7.2Enantiomeric forms of arabinose
Ο
CΗ 2 ΟΗ
ΟΗ ΟΗ
ΟΗ
Ο
CΗ 2 ΟΗ
ΟΗ
ΟΗ
ΟΗ
Ribose Arabinose
Fig. 7.3Diastereomers: structures of ribose and arabinose
O
OH
OH
OH
OH
CH 2 OH
Glucose
O
OH
OH
OH
CH 2 OH
Galactose
OH
Fig. 7.4Epimers: structures of galactose and glucose
7.3.2 Chemical Reactivity
Carbohydrates are rather stable in solid state, at neutral pH and room temperature,
but when they appear in aqueous matrices such as food, they can easily react with
acids, bases and proteins to give different reactions. Some of them are relevant in
wine chemistry and are mentioned below:
- Reaction with acids:in acid medium, disaccharidesand polysaccharides may be
hydrolyzed to monosaccharides, which in turn may be dehydrated and degraded