Food Chemistry

268 4 Carbohydrates

( 4. 44 )

reactive and provide a great number of secondary
products by aldol condensations (retro-reactions)
and intramolecularCannizzaroreactions.
The compounds formed in fructose syrup
of pH 8–10 heated for 3 h are listed in Ta-
ble 4.12. The cyclopentenolones are typical
caramel-like aroma substances. The formation
of 2-hydroxy-3-methyl-2-cyclopenten-1-one as
an example is shown in Formula 4.46. The
compound 1,3,5-trideoxy-2,5-hexulose is formed
as an intermediate via the aldol condensation

Table 4.12.Volatile reaction products obtained from
fructose by an alkali degradation (pH 8–10)

Acetic acid

Hydroxyacetone

1-Hydroxy-2-butanone

3-Hydroxy-2-butanone

4-Hydroxy-2-butanone

Furfuryl alcohol

5-Methyl-2-furfuryl alcohol

2,5-Dimethyl-4-hydroxy-3-(2H)-furanone

2-Hydroxy-3-methyl-2-cyclopenten-1-one

3,4-Dimethyl-2-hydroxy-2-cyclopenten-1-one

3,5-Dimethyl-2-hydroxy-2-cyclopenten-1-one

3-Ethyl-2-hydroxy-2-cyclopenten-1-one

γ-Butyrolactone

of 2 molecules of monohydroxyacetone (or the

isomer 2-hydroxypropanone). The linking of

the C-atoms 6 and 2 then leads to a carbocycle

which yields the target compound on water

elimination. Analogously, the substitution of

l-hydroxy-2-butanone or 3-hydroxy-2-butanone

for one molecule of hydroxyacetone can give

rise to 2-hydroxy-3-ethyl- or 2-hydroxy-3,4-

dimethyl-2-cyclopenten-1-one.

Among other compounds, C-3 fragments are also

precursors for the formation of 4-hydroxy-2,5-

dimethyl-3(2H)-furanone (II, furaneol), which

can be formed, e. g., from 2-hydroxypropanal

and its oxidation product, 2-oxopropanal (I in

Formula 4.47). The substitution of 2-oxobutanal

for 2-oxopropanal yields the homologous

ethylfuraneol. In a similar way, 3-hydroxy-

4,5-dimethyl-2(5H)-furanone (sotolon) can be

formed from 2,3-butanedione (diacetyl) and

glycolaldehyde (Formula 4.48).

Saccharinic acids are specific reaction prod-

ucts of monosaccharides in strong alkalies,

particularly of alkaline-earth metals. They are

obtained in each case as diastereomeric pairs

by benzilic acid rearrangements from deoxy-

hexodiuloses according to Formula 4.48a. In

fact, 1-deoxy-2,3-hexodiulose yields saccharinic

acid, 3-deoxy-1,2-hexodiulose yields metasac-

charinic acid and 4-deoxy-2,3-hexodiulose yields

isosaccharinic acid (Formula 4.48b).