Produce Degradation Pathways and Prevention

Flavor and Volatile Metabolism in Produce 165

effort spent on fresh citrus fruit [57,112]. The flavor of fresh citrus is a result of the

combination of peel essential oil, which is expressed during rupture of the ductless

oil glands located in the outer portion (flavedo) of the fruit, and volatile constituents

present within the fruit in juice sacs [57]. A large number of compound classes

contribute to citrus flavors, including terpenes, alcohols, aldehydes, esters, ketones,

and others. Results of extensive compositional studies on the various essential oil

fractions and juices have indicated that only a relatively few volatile compounds are

important in characterizing the flavors of individual citrus varieties. Predominant

aroma constituents of five major citrus varieties are presented in Table 6.2.

A more extensive review of the flavor chemistry of the various citrus varieties

was presented by Shaw [57]. Orange and grapefruit flavors are delicate and complex,

TABLE 6.2
Predominant Aroma Components of Major Citrus Varieties

Orangea Grapefruitb Manderinc Lemond Limee

Acetaldehyde Ethyl butanoate Acetaldehyde Citral (mixture of
neral and geranial)

Citral (mixture
of neral and
geranial)
Decanal p-1-Methene-8-thiol Octanal Geranial Germacrene B
(Z)-3-Hexenal 1-Heptane-3-one Decanal β-Pinene Linalool
Ethyl butanoate Ethyl butanoate Thymol γ-Terpinene β-Pinene
Ethyl 2-methyl-
propanoate

4-Mercapto-4-methyl-

pentane-2-one

Methyl N-methyl-

anthranilate

Geranyl acetate β-Myrcene

(S)-Ethyl 2-
methyl-butanoate

trans-4,5-Epoxy-(E)-

2-decenal

β-Pinene Neryl acetate

Wine lactonef Wine lactone γ-Terpinene Bergamotene
(R)-Limonine α-Sinensal Caryphyllene
(R)-α-Pinene Ethyl-2-methyl-
butanoate

α-Bisabolol

trans-4,5-Epoxy-
(E)-2-decenal

3-sec-Butyl-2-

methoxypyrazine

Carvyl ethyl ether

3-Isopropyl-2-

methoxypyrazine

8-p-Cymenyl ethyl

ether

(Z)-3-Hexenal Fenchyl ethyl ether

Linalyl ethyl ether

Myrcenyl ethyl ether

α-Terpinyl ethyl ether

Methyl epijasmonate

Note:Components are not necessarily listed in order of importance.
aData from Hinterholzer and Schieberle [113] and Buettner and Schieberle [114].
bData from Buettner and Schieberle [49].
cData from Shaw [57], Wilson and Shaw [115], and Schieberle et al. [116].
dData from Mussinan et al. [119].
eData from Clark et al. [117] and Chisholm et al. [118].
f 3 α,4,5,7α-Tetrahydro-3,6-dimethyl-2(3H)-benzofuranone.