2009_Book_FoodChemistry

18.1 Fruits 841
18.1.2.6.9 Strawberries
The concentrations of the odorants in strawberry
juice are given in Table 18.30. With a solution of
the first 11 compounds listed in the table, the original
aroma was largely approximated. If HD3F
was missing, the mixture smelt green and fruity
and if (Z)-3-hexenal was missing, the caramellike/sweetish
note of HD3F dominated.
The HD3F concentration depends on the variety
of strawberry. Values between 1.1 and
33.8mg/kg were found. The red parts of the
fruit are richer in HD3F than the white parts.
The strawberry aroma changes on heating due
to an increase in HD3F, formation of (E)-βdamascenone,
(E,E)-2,4-decadienal and guaiacol
as well as great losses of (Z)-3-hexenal and the
esters (Table 18.30). A freeze/thaw process also
changes the aroma as a result of a great increase
in HD3F and degradation of (Z)-3-hexenal.
18.1.2.6.10 Pineapples
A model on the basis of the compounds listed in
Table 18.31 reproduces the aroma of pineapples.
Table 18.30. Concentrations of odorants in fresh and
heated strawberry juice
Compound
Concentration
(mg/kg)
Fresh
Heated a
4-Hydroxy-2,5-dimethyl- 16.2 29.4
3(2H)-furanone (HD3F)
(Z)-3-Hexenal 0.333 0.025
Methyl butyrate 5.0 1.0
Ethyl butyrate 0.41 0.048
Isobutyric acid ethylester 0.043 0.012
2-/3-Methylbutyric acid 0.048 0.007
methylester
2-/3-Methylbutyric acid 0.007 0.0012
ethylester
Acetic acid 74.5 74.9
2,3-Butandione 1.29 0.85
Butyric acid 1.83 1.79
2-/3-Methylbutyric acid 2.24 2.20
(E)-β-Damascenone <0.1 5.4
(E,E)-2,4-Decadienal <0.1 4.1
Guaiacol 0.8 2.8
a 100 ◦ C, 30 min (reflux).
Table 18.31. Odorants of pineapples
Compound Concen- Aroma
tration value a
(µg/kg)
4-Hydroxy-2,5-dimethyl-3(2H)-
furanone 26,800 2680
2-Methylpropionic acid
ethyl ester 48 1400
2-Methylbutyric acid ethyl ester 157 1050
2-Methylbutyric acid
methyl ester 1190 595
(E,Z)-1,3,5-Undecatriene 8.9 445
β-Damascenone 0.083 111
Butyric acid ethyl ester 75 75
2-Methylpropionic acid
methyl ester 154 24
Octanal 19 2
δ-Ocalactone 78 <1
δ-Decalactone 32.7 <1
Vanillin 6 <1
a
Aroma value: quotient of the concentration and
orthonasal odor threshold value in water.
Omission experiments have shown the five odorants
with the highest aroma values shown in Table
18.31 are the key aroma substances.
18.1.2.6.11 Cherries, Plums
The compounds essentially involved in the
aroma of cherries are benzaldehyde, linalool,
hexanal, (E)-2-hexenal, phenylacetaldehyde,
(E,Z)-2,6-nonadienal, and eugenol (Table 18.32).
On heating cherry juice or in the making of jams,
the concentration of benzaldehyde increases due
to the hydrolysis of amygdalin and prunasin
Table 18.32. Odorants of cherry juice and jams made
from it a
Aroma substance Juice (µg/kg) Jam (µg/kg)
Benzaldehyde 202 1510
Linalool 1.1 13.1
Hexanal 5.6 0.2
(E)-2-Hexenal 8.5 3.8
Eugenol 10.0 4.9
a Fruit content: 50 w/w per cent.