How_It_Works_Issue_99_2017

DID YOU KNOW? Olive oil should ideally be stored in coloured glass bottles, which block out UV light and oxygen
The history of olive oil production
People have been extracting the oil from olives
for over 5,000 years, and unsurprisingly the
method has changed quite a lot during that
time. In the past, the olives were crushed into
a paste using large circular stones of granite
that were turned by donkeys. The paste was
then separated from the oil and water using a
method called pressing. The paste was spread
onto discs of hemp or coconut fibre, which
were then stacked and placed in a press to
squeeze out the liquid. The oil and water could
then be separated quite easily as the two do not
mix. Today, some mills still practice the
pressing method, but their discs are made of
synthetic fibres and a more powerful hydraulic
press is used.
“Some plants can
process three tons
of olives in just
one hour”
Millstones have been replaced
with stainless steel rollers in
modern oil mills
Removing debris
Any leaves, twigs and
other types of debris are
filtered out through
grids prior to crushing.
Crushing
The olives are crushed
and ground into a pulp
using stainless steel
rollers, releasing the oil
from the olive cells.
Malaxing
Water is mixed with the
paste for 20-45
minutes to allow small
oil droplets to combine
into bigger ones.
Decanting
As water and oil do not
mix they can be easily
separated from each
other and the solid
material, although this
may also be done using
a centrifuge.
Pressing
Traditionally, in place of
decanting, the pulp is
sandwiched vertically
between layers of hemp
mats and squeezed to
extract the oil.
© Thinkstock; Illustration by Adrian Mann
Centrifugation
Instead of decanting, most
modern facilities use a
centrifuge that spins at
high speeds to separate
the oil from the pulp.
Pomace
The solid material extracted is
called pomace and contains a
low-quality residual oil that
can be extracted later.
WWW.HOWITWORKSDAILY.COM
How It Works | 035