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840 18 Fruits and Fruit Products

(18.38)

γ-octalactone, γ-decalactone, γ-dodecalactone,

δ-octalactone and δ-decalactone.

and hexyl hexanoate (69.6).

18.1.2.6.7 Peaches

The aroma of peaches is characterized by

γ-lactones (C 6 –C 12 ) and δ-lactones (C 10 and

C 12 ). The main compound in the lactone fraction

is (R)-1,4-decanolide, which has a creamy,

fruity, peach-like odor. Other important compounds

should be benzaldehyde, benzyl alcohol,

ethyl cinnamate, isopentyl acetate, linalool,

α-terpineol, α- andβ-ionone, 6-pentyl-α-pyrone

(Formula 18.39, VIII), hexanal, (Z)-3-hexenal,

and (E)-2-hexenal. Aroma differences in different

varieties of peaches are correlated with the different

proportions of the esters and monoterpenes.

In the case of nectarines (Prunus persica L.,

Batsch var. nucipersica Schneid), the lactones

γ-C 8 –C 12 and δ-C 10 belong to the compounds

with the highest aroma values.

18.1.2.6.8 Passion Fruit

The aroma of the yellow fruit (Passiflora edulis

var. flavica) is supposed to be superior to that of

the crimson fruit (Passiflora edulis var. edulis).

Compounds that contribute to the aroma of both

varieties are β-ionone and the following esters

(% of the volatile fraction): ethyl butyrate (1.4),

ethyl hexanoate (9.7), hexyl butyrate (13.9),

(18.39)

Four stereoisomeric megastigmatrienes have

been found in crimson passion fruit. A mixture of

the isomers IXa and IXb (Formula 18.39) gives

a rose-like aroma, that has a hint of strawberries

in it (threshold = 100 µg/kg; water).

The following S-containing aroma substances

have been isolated from the yellow fruit: 3-

methylthiohexane-1-ol which probably gives rise

to 2-methyl-4-propyl-1,3-oxathianes (cis/trans

isomers in the ratio of 10:1) (Xa, b: Formula

18.39). Of the two cis isomers, only the

2R,4S-isomer (Xb), which has a sulfurous

herb-like odor (threshold = 4 µg/kg; water), has

been found in the fruit. However, the aroma note

more typical of passion fruit is exhibited by the

2S,4R-isomer (Xa).

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