Olives and Olive Oil - Tropical and Subtropical Fruits: Postharvest Physiology, Processing and Packaging - page 486

Figure 26.1. Color evolution in olive fruits: intense green → light green → purple → black. For
color detail, please see color plate section.

following fertilization and initial fruit formation (Rapoport,
2008).
The olive growth and development period is very long
(from 6 to 7 months) compared with other stone fruits. As
with most drupes, it has a double sigmoid growth curve
with three stages. During the first stage, its weight in-
creases considerably. This is followed by a maintenance
stage, and finally by a phase of rapid growth mainly due
to an increase in cell volume. Once the fruit has reached
its definitive weight, it may experience fluctuations, which
are essentially derived from changes in humidity (Roca and
Mınguez-Mosquera, 2003).
During fruit maturation, the fruit increases its oil
content, while its color changes from intense green to
yellowish green and finally acquires a blackish purple tone
(Fig. 26.1). Chlorophylls and carotenoids are the pigments
responsible for the color of the green tissue. A progressive
decrease in the concentration of those pigments, especially
in chlorophylls, gives the fruit its greenish yellow color
as it matures (Mınguez-Mosquera and Garrido-Fernandez,
1989). This finally leads to the synthesis of anthocyanin
compounds. Small reddish marks begin to appear on the
epidermis (speckling) and progressively cover the entire
fruit surface with a purple hue until the fruit reaches total
maturity and turns black. Finally, anthocyanin synthesis
reaches the fruit interior, leading to pigmentation of the
entire mesocarp. The maturation period is considered to
be from the first appearance of purple marks until the final
color of both the skin and the pulp is reached.
The biochemistry of the olive tree is singular. From
the photosynthetic point of view olive is one of the few
species capable of synthesizing both polyols (mannitol)
and oligosaccharides (raffinose and stachyose) as the fi-
nal products of the photosynthetic CO 2 fixation in the leaf
cell. These carbohydrates, together with sucrose, can be ex-
ported from the leaves to the fruits to fulfill the metabolic
requirements for oil synthesis. Conversely, contrary to
oilseeds, which are absolutely dependent on the leaves to

supply photoassimilates for the synthesis of storage oil, de-
veloping olives contain active chloroplasts capable of fixing
CO 2 (Sanchez and Harwood, 2002).
The olive mesocarp or pulp represents between 70% and
88% of the fruit's total weight. It is primarily made up
of water (60-75%) and lipids (oil) (10-25%). The olive's
chemical composition differs from that of other drupes in
that it has relatively low sugar levels (3-4%) compared
with other drupes (12% or more), high lipid content, and a
characteristic bitter taste. Composition of raw, canned, and
pickled olives is given in Table 26.1.
The 98-99% of lipid fraction consists of a mixture of
triglycerides, free fatty acids, waxes, mono- and diglyc-
erides, sterol esters, and terpene alcohols and phospholipids
(Sanchez and Harwood, 2002). The fatty acids mainly form
esters with glycerol, producing glycerides (mono-, di-, and
triglycerides) and phospholipids. Fatty acids also form es-
ters with other linear alcohols (waxes) or terpene alcohols.
The fatty acids, which are found in larger proportions (such
as glycerides) are oleic (C18:1), linoleic (C18:2), palmitic
(C16:0), palmitoleic (C16:1), and stearic (C18:0); oleic acid
has the highest concentration (55-83% of the oil weight),
followed by palmitic (7.5-20%) and linoleic (3.5-21%).
Total saturated triglycerides are absent, and the concentra-
tion of saturated fatty acids at position 2 of the glycerine
molecule is low.
The olive fruit and processed products, table olive and
olive oil, are an important source of linoleic, an essential
fatty acid, and monounsaturated fatty acids, making olive
and olive products having high biological and nutritive
values.
Sugars (3-6%) are of great interest in the processing
of table olives since they constitute the available substrate
to be fermented by micro-organisms. The fiber fraction
(1-4%) (Guillen et al., 1992) and the pectic substances
(0.3-0.6%) (Mınguez-Mosquera et al., 1976) constitute a
group qualitatively important because of the influence on
texture, one of the attributes of sensory quality in table