Food Chemistry

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 ori-
ginal aroma was largely approximated. If HD3F
was missing, the mixture smelt green and fruity
and if (Z)-3-hexenal was missing, the caramel-
like/sweetish note of HD3F dominated.
The HD3F concentration depends on the va-
riety of strawberry. Values between 1.1and
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)-β-
damascenone, (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 Heateda

4-Hydroxy-2,5-dimethyl- 16. 229. 4
3(2H)-furanone (HD3F)
(Z)-3-Hexenal 0. 333 0. 025
Methyl butyrate 5. 01. 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. 574. 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. 15. 4
(E,E)-2,4-Decadienal < 0. 14. 1
Guaiacol 0. 82. 8
a 100 ◦C, 30 min (reflux).

Table 18.31.Odorants of pineapples

Compound Concen- Aroma

tration valuea

(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

aAroma value: quotient of the concentration and

orthonasal odor threshold value in water.

Omission experiments have shown the five odor-

ants with the highest aroma values shown in Ta-

ble 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 ita

Aroma substance Juice (μg/kg) Jam (μg/kg)

Benzaldehyde 202 1510

Linalool 1. 113. 1

Hexanal 5. 60. 2

(E)-2-Hexenal 8. 53. 8

Eugenol 10. 04. 9

aFruit content: 50 w/w per cent.