Olives and Olive Oil - Tropical and Subtropical Fruits: Postharvest Physiology, Processing and Packaging - page 494

(0.3-0.4%, w/v) (Rejano-Navarro et al., 2008). This tech-
nique also avoids the peeling of olives during the following
debittering with lye, which is a problem that is observed in
some varieties, such as Manzanilla, when the lye is applied
to fruits not subjected to a resting period of 2-5 days before
treatment (Fernandez-Dıez et al., 1985). Some studies have
shown that it is also possible to store green olives for sev-
eral weeks using cold rooms and controlled atmospheres
(Nanos et al., 2002; Dourtoglou et al., 2006).
To produce ripe olives, fruits are commonly preserved in
brine before oxidation, and a fermentative process similar
to that of natural black olives takes place. Nevertheless, this
preservation can also be done in acidified water (de Castro
et al., 2007). In the United States, a salt-free storage of
olives combining acidulated water (lactic and acetic acid)
in anaerobic conditions is used (Vaughn et al., 1969).

and low pH ( 3.5 units). However, nowadays the stability

of the product is often guaranteed by pasteurization.

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Natural black olives or Greek style
For preparing these types of olives, the fruits are harvested
by hand when black ripe, but not overripe. They are washed
and placed into brine with 8-10% NaCl, where a sponta-
neous fermentation takes place. A diverse number of mi-
crobes grow in these brines, although yeasts are the domi-
nant micro-organisms, being always present throughout the
process. The removal of the bitterness is slow and only par-
tial. It is achieved by solubilization of the oleuropein into
the brine. Once the bitterness has been sufficiently weak-
ened, fruits are ready to be marketed. The fruit color is
improved by aerating the olives for no more than 48 hours.
Lastly, the olives are packed in barrels or internally var-
nished cans filled with 8% of fresh brine and pH 4-4.2. To
assure good conservation of the packed product pasteuriza-
tion can be employed or the addition of sodium sorbate to
reach a level of 0.05% (as sorbic acid) in the equilibrium.
The traditional brining is carried out under anaerobic con-
ditions, however, an aerobic method can be applied, using
a central column in the fermenter through which air is bub-
bled. With this system, a final product with better quality is
obtained.

Table olive processing
In general most processes involved in preparing table olives
are mainly intended to remove the olive's natural bitter-
ness, as described earlier. In this section, a summary of
the main trade preparations for table olives, highlighting
the most important parts of each process are described (see
Fig. 26.4). At the same time, other traditional types of table
olive processing are included. A complete description of
the different types of table olive processing can be found
in Fernandez-Dıez et al. (1985), Garrido-Fernandez et al.
(1997), and Sanchez-Gomez et al. (2006).

Olives darkened by oxidation or Californian style
The essential operation of this preparation is the oxidation.
Fruits are successively treated with 1-2% NaOH solutions
for varying periods of time to achieve a progressive pene-
tration of the lye into the flesh. During the intervals between
lye treatments fruits are put into water and oxidized by in-
jecting air under pressure into water. This oxidation of the
phenolic compounds allows a complete blackening of the
fruit skin and a uniform coloration of the flesh. After the last
lye treatment, olives are washed several times with water to
remove most of the sodium hydroxide and to lower the pH
in the flesh to around eight units. Generally, 0.1% of ferrous
gluconate or lactate is added to the last wash to stabilize
color. The black olives (whole, pitted, slices, quarters or
paste) are packed with a liquid containing 2-4% NaCl and
10-40 ppm of iron to prevent color deterioration. The pH
values are between 5.8 and 7.9, and the product has to be
sterilized.

Treated green olives in brine or Spanish-style
This process is characterized by fruits being transported
to elaboration industries, sorted, partially graded by size
and treated with a diluted (2-5% w/v) aqueous solution
of sodium hydroxide to remove bitterness and to increase
the permeability of the cell wall. The treatment lasts un-
til the lye penetrates the pulp to a depth of two-thirds to
three-fourths of the distance from the olive surface to pit.
After alkali treatment, fruits are washed with tap water to
eliminate the excess of the lye remaining in the flesh. The
number and the time devoted to washing waters vary, al-
though the current trend is to reduce them to only one, which
can last from 12 to 15 hours. When the washing waters are
removed, olives are immersed in brine, which consists of
an aqueous solution of sodium chloride (10-11% w/v) and
where olives undergo lactic acid fermentation. Lactic acid
bacteria and yeast are responsible for fermentation. Then
the fruits are graded by size and sorted, and the final prod-
uct (occasionally pitted and stuffed) is packed by different
forms. Traditionally, the packed olives were stabilized by
high values of free acidity (0.5-0.7%) and NaCl (5-7%),

Dehydrated black olives
This type of table olive of Greek origin is prepared using
overripe fruits. Olives are washed and placed in baskets
with alternating layers of dry salt equivalent to 15% of the