Flavor and Volatile Metabolism in Produce 163
have been established as aroma-impact components, but numerous other aroma
constituents, such as C 6 aldehydes, aliphatic alcohols, and terpenes, may contribute
to the aromas of peaches and nectarines [73–75]. Recently, β-damascenone and
6-dodecenyl-γ-lactone were reported as additional predominant aroma components
of peach aroma [75].
6.3.1.3 Melon, Cucumber, and Squash
The key aroma components of cantaloupe (a.k.a. muskmelon or rockmelon) (Cucu-
mis melo) [76–81] and honeydew (Cucumis inodorus) [82] cultivars have been
reported [76–78]. The fruity-smelling branched esters ethyl 2-methylbutanoate and
methyl 2-methylpropanoate were reported as predominant aroma compounds. Addi-
tional important esters include ethyl 2-methylpropanoate, 2-methylpropyl acetate,
and several thio-esters that vary among varieties.
In contrast to cantaloupe and honeydew melons, watermelon (Citrullis vulgaris)
[83,84], cucumber (Cucumis sativus) [76,85], and pumpkin and squash (Cucurbita spp.)
[86] do not contain esters as part of their characteristic aromas. Instead, their typical
aroma constituents are primarily generated upon tissue disruption via lipoxygenase
pathways, leading to compounds having characteristic cucumber- and watermelon-like
aromas, such as (E,Z)-2,6-nonadienal and (Z,Z)-3,6-nonadienal, respectively, among
numerous other C 6 and C 9 volatile aldehydes and alcohols that affect the aromas.
6.3.1.4 Tomato
The flavor of tomato (Lycopersicon esculentem Mill.) is mainly attributed to its
aroma volatiles, sugars, and acids. DMHF is an essential component of fresh tomato
aroma [31], but many additional compounds have been reported as major contribu-
tors, including (Z)-3-hexenal, hexanal, β-ionone, β-damascenone, 1-penten-3-one,
3-methylbutanal, (E)-2-hexenal, phenylacetaldehyde, 2-phenylethanol, 2-isobutyl-
thiazole, 6-methyl-5-hepten-2-ol, 1-nitrophenylethane, 3-(methylthio)propanal
(methional), (E)-2-heptenal, (E,Z)- and (E,E)-2,4-decadienal, trans- and cis-epoxy-
(E)-2-decenal, 1-octen-3-one, 3-methylbutanoic acid, and (Z)-1,5-octadien-3-one
[87–92]. In regard to tomato flavor quality (preference), Mayer et al. [92] reported
that higher levels of the 2,4-decadienal isomers, 1-penten-3-one, and DMHF had a
positive influence, whereas phenylacetaldehyde, 2-phenylethanol, and 2-isobutyl-
thiazole negatively affected fresh tomato aroma.
6.3.1.5 Small Fruit
The small fruits are composed of over 10 genera and include strawberries, raspber-
ries, blackberries, blueberries, and others. Latrasse [56] reviewed the flavor chemistry
of 20 species of wild and cultivated berries. The flavor of berries was also the subject
of a review by Honkanen and Hirvi [93]. This section will be restricted to the
discussion of strawberry flavor, since this fruit has undergone extensive study in
recent years. The reader is encouraged to review the recent literature on raspberry
(Rubus idaeus L.) [94–97], blackberry (Rubus fructicosus) [98], and blueberry (Vic-
cinium spp.) [99,100] flavors.