Passion Fruit - Tropical and Subtropical Fruits: Postharvest Physiology, Processing and Packaging - page 316

-carotene in yellow passion fruit
led Gross (1987) to consider the carotenoid pattern as un-
common. Most fruits have

The predominance of ζ ethyl hexanoate (9.3%), and cis-edulan (5.6%) prevailed in

the purple fruit. In yellow passion fruit, methyl hexanoate
(32.9%), ( E )-methyl-2-hexenoate (11.7%), and methyl ben-
zoate (11.2%) predominated, while in the banana passion
fruit, the major volatiles were ( Z )- α -ocimene (56.6%),
hexyl butanoate (16.8%), and hexyl hexanoate (13.9%).
Aside from biosynthesized volatile compounds, trans-
formation or degradation of nonvolatile precursors ac-
counts for many of the passion fruit volatiles. Some of
the volatiles are likely to be degradation products of
carotenoids (Murray et al., 1972), such as linalool, β -
ionone, dihydro- β -ionone, and the lactone of 2-hydroxy-
2,6,6-trimethylcyclohexylideneacetic acid (dihydroactinid-
iolide), an oxidation product of

-cryptoxanthin,
lycopene, or violaxanthin as the main carotenoid.
Cyanidin 3-glucoside was shown to be responsible for
the purple color of the rind of P. edulis, accounting for
97% of the total anthocyanin content (Kidoy et al., 1997).
Small amounts of cyanidin 3-(6 -malonylglucoside) (2%)
and pelargonidin 3-glucoside (1%) were also found.

β -carotene, β

Volatile compounds
The volatile compounds responsible for the intense, fra-
grant, and distinctive aroma/flavor of passion fruit have
been investigated widely.
Summarizing knowledge of the volatile flavoring con-
stituents of passion fruit at the time, Casimir et al. (1981)
listed 13 nonterpenoid alcohols, 10 cabonyl compounds,
6 carboxylic acids, 43 esters, 3 lactones, 9 terpenoids, and
4 other compounds for purple passion fruit. In the yellow
fruit, 21 nonterpenoid alcohols, 23 carbonyl compounds,
21 carboxylic acids, 38 esters, 9 lactones, 12 terpenoids,
and 33 other compounds were found.
A compendium in 1990 listed 11 hydrocarbons, 85 es-
ters, 16 aldehydes and ketones, and 34 alcohols and acids
for purple passion fruit (Shibamoto and Tang, 1990). In the
yellow fruit, 15 hydrocarbons, 51 esters, 28 aldehydes and
ketones, 74 alcohols and acids, and 24 miscellaneous com-
pounds were found. Casimir and Whitfield (1978) reported
that out of some 300 volatile flavoring constituents of pas-
sion fruit drinks, only 22 were found likely to contribute
to the passion fruit flavor, with several esters present in
the juice at relatively high concentrations having negligible
flavor impact values.
With a flavor often considered more pleasing, the pur-
ple passion fruit differs from the yellow fruit in volatile
composition. It has higher levels of the major esters: ethyl,
butyl, and hexyl butanoates, butyl and hexyl hexanoates,
and of the terpene ketones

β -ionone, these compounds

being detected in both purple and yellow pas-

sion -ionone and 1,1,6-trimethyl-1,2-

dihydronaphthalene (3,4-dehydroionene), a possible degra-
dation product of

fruit. Dihydro- β

-ionone, has been found only in pur-
ple passion fruit. Other compounds, such as edulans and
megastigmatrienes (substituted cyclohexenes), could also
be derived from carotenoids.
Two other classes of flavor precursors can be transformed
into important aroma compounds of passion fruit (Engel
and Tressl, 1983; Herderich and Winterhalter, 1991; Chas-
sagne et al., 1996). Nonconjugated polyhydroxylated ter-
penoids (polyols) on heat treatment under acidic conditions
can form numerous aroma compounds. Moreover, acid-
labile glycosidically bound compounds (e.g., glycosides of
monoterpene alcohols) can be easily transformed to free
volatiles by means of acid or enzymatic hydrolysis.

β

Compositional changes during ripening
During the ripening of purple passion fruit, sucrose de-
creased while fructose and glucose increased (Shiomi et al.,
1996a). Citric and malic acids increased slightly during the
early stage of ripening but decreased thereafter. Amino
acids did not change significantly, with the exception of
proline, which increased rapidly during the late stage of
ripening.
Comparing yellowish green (immature), partially purple
(partially mature), and purple (ripe) fruits taken from the
same orchard, the immature fruits had lower proportion
of juice, o Brix, o Brix/acid ratio, reducing and total sugars,
ascorbic acid, and carotene (Pruthi, 1963). These fruits were
more acidic and inferior in flavor compared to the partially
and fully ripe fruits.
The volatile composition changes during maturation, the
compounds of greatest flavor significance reaching max-
imum concentrations in the ripe fruit. Anthocyanins and
carotenoids also increase during ripening (Pruthi, 1963).

-ionone.
Some important flavor constituents of the purple passion
fruit are not found in the yellow fruit: 2-heptyl acetate, bu-
tanoate, and hexanoate, the edulans, dihidroionone, 1,1,6-
trimethyldihydronaphthalene and the megastigmatrienes.
There are also differences in the terpene hydrocarbons with
respect to the fruit type.
A recent study using dynamic headspace solid-phase
microextraction followed by thermal desorption gas
chromatography-quadrupole mass spectrometry tentatively
identified 51 volatiles in purple passion fruit, 24 in yellow
passion fruit, and 21 in banana passion fruit (Pontes et al.,
2009). Hexyl butanoate (23.2%), hexyl hexanoate (18.4%),

β -ionone and dihydro- β