Aroma Volatiles - Fruit Ripening: Physiology, Signalling and Genomics - page 63

5 Aroma Volatiles

Bo Zhang and Kun-Song Chen*
Laboratory of Fruit Quality Biology, Zhejiang University, Hangzhou,
PR China

As an important factor for quality,
together with textural and visual cues and
with sugars and acids, the aroma volatiles
of fruits have a major impact on consumer
preference (see Plate 2). Fruit aroma is
determined by a complex mixture of
volatiles, including aldehydes, alcohols,
esters, ketones, lactones and terpenoids.
Although the production of these com-
pounds accounts for only 10 -7 -10 -4 % of
the fresh fruit weight, these compounds
can be detected by the human olfactory
system and are regarded as the char-
acteristic fl avours of the fruit (Jiang and
Song, 2010). Identifi cation of the character-
impacting aroma volatiles of major fruit
species has been studied intensively, and
volatile compounds are known to be
infl uenced by various factors such as
cultivar, maturity stage, postharvest treat-
ment and analysis technique. Generally,
the content of most volatile compounds
increases at the onset of fruit ripening and
peaks either at or shortly before full
ripening (Goff and Klee, 2006).
Fruit aroma volatiles are represented by
fatty acid derivatives, terpenoids and
amino acid derivatives, and the diversity of
their origins within the metabolome has
been summarized by Schwab et al. (2008).
Improving fruit aroma quality is becoming
an important goal of breeding and

5.1 Introduction

Plants are multifaceted chemical factories
that produce at least 1000 volatile com-
pounds, and the molecules involved in the
biosynthesis and release of these volatiles
comprise more than 1% of plant secondary
metabolites (Qualley and Dudareva, 2009;
Dicke and Loreto, 2010). Some plants
allocate up to 10% of their carbon to
the production of volatile secondary
metabolites (Firn and Jones, 2006). Several
years ago, an argument was raised focusing
on the role of volatile compounds released
by plants. This argument was presented in
an article entitled, 'Plant volatiles: a lack
of function or a lack of knowledge?'
(Pichersky et al. , 2006). In recent years,
thanks to the development of integrative
biological approaches, more and more
papers regarding volatiles have been
published, giving rise to a molecular under-
standing of the function of volatiles. In
March 2010, a special issue of Trends in
Plant Science , entitled 'Induced biogenic
volatile organic compounds from plants',
discussed the role of volatiles. These
studies have formidably enhanced our
knowledge of the volatiles that are involved
in plant responses to biotic and abiotic
factors and in plant communication with
other organisms.