Aroma Volatiles - Fruit Ripening: Physiology, Signalling and Genomics - page 72

nectarine fruit growth, whilst fruity-note
lactones such as decalactone and
dodecalactone accumulated greatly upon
further maturity (Visai and Vanoli, 1997).
The sesquiterpene valencene plays an
important role in the overall aroma quality
of orange fruit and accumulates during fruit
development. A minor valencene peak was
found in young Valencia orange fruit,
followed by signifi cantly higher levels at
approximately 1-2 months after fruit colour
break and continued accumulation until
the fruits were fully mature (Sharon-Asa et
al. , 2003). In strawberry fruit, the character
aroma furanones and esters increased
signifi cantly and were closely correlated
with skin colour development (Ménager et
al. , 2004).
The generation of volatile compounds is
greatly infl uenced by multiple environ-
mental factors such as light and tem-
perature, and the effects of these factors on
the emission of plant volatiles have been
reviewed by Holopaninen and Gershenzon
(2010). During peach fruit development,
the fruits were bagged under different
levels of sunlight transmission (15, 50 and
80%) at approximately 50 days after full
bloom, and non-bagged fruits were exposed
to direct sunlight (100%) (Jia et al. , 2005).
The results showed that bagging did not
infl uence the total aroma volatiles released
by whole fruit and the fl esh tissue, but
signifi cant differences were observed in the
skin tissue. Signifi cantly higher levels of J -
and G -decalactone and total aroma volatiles
were found in peach fruit treated in bags
with 15% transmission of sunlight,
indicating that bagging can improve aroma
quality during fruit growth. Differences in
the volatile profi les of bagged fruit may be
caused by accelerated ripening by bagging
(Jia et al. , 2005; Wang et al. , 2010). In
tomato fruit, a signifi cantly higher content
of hexanal was observed in traditional
open-fi eld conditions compared with
protected cultivation in a screenhouse (a
system usually used to prevent virus
transmission by thrips and whitefl ies)
(Cebolla et al. , 2011).
In addition, preharvest calcium sprays
enhanced the accumulation of the volatiles

contributing to the overall aroma quality,
indicating a suitable procedure for the
improvement of fruit aroma at harvest.
'Fuji' apple fruits were sprayed weekly
with CaCl 2 (1.6%, w/v) from 81 days after
full bloom until the commercial harvest
date, resulting in signifi cant increases in
ester production, both quantitatively and
qualitatively (Ortiz et al. , 2011). The
enhanced emission of eight straight-chain
esters and four branched-chain esters was
suggested to be caused by increased
activity of pyruvate decarboxylase (PDC)
and ADH, leading to a better supply of
alcohols and acyl-CoAs for ester formation
in calcium-treated apple fruit (Ortiz et
al. , 2011). A recent study by Salas et al.
(2011) showed that application of
aminoethoxyvinylglycine to apple trees
4 weeks prior to harvest resulted in a
reduction of volatile compounds during
postharvest storage.

5.4.2 Ethylene

Ethylene is the major regulator of fruit
ripening in many fl eshy fruits. The
relationship between ethylene and the
biosynthesis of volatiles in ripening fruit
has been reported in apricot (González-
Agüero et al. , 2009), citrus (Mayuoni et al. ,
2011), kiwifruit (Zhang et al. , 2009), peach
(Zhang et al. , 2010), tomato (Qin et al. ,
2012) and other fruits (reviewed by
Defi lippi et al. , 2009a). The evidence for a
regulatory role of ethylene in the
development of aroma quality is based
mainly on the accumulation of aroma
volatiles during fruit ripening and the
effects of ethylene and its inhibitors on
changes in volatile compounds.
The production of aroma volatiles was
compared in 15 Charentais melon cultivars
with different ethylene emission and
ripening dates, and a large reduction (49-
87%) of volatiles was found in long-shelf-
life cultivars compared with the original
type and mid-shelf-life cultivars (Lucchetta
et al. , 2009). Differences in the aroma
volatiles of climacteric and non-climacteric
melon fruit have also been analysed