Page 416 - Biosystems Engineering

Phenolic Substances fr om Olives & Olive Mill Pr oducts 393

“Virgin olive oil” is the oil extracted exclusively with mechanical
techniques; when one virgin olive oil has specific chemical-analytical
and good organoleptic characteristics, it can be sold as extra-virgin,
which indicates that it is of superior quality (UE Regulation 2003).
The olive oil industry also produces a large amount of by-products.
It is estimated that for every 100 kg of olives worked, 35 kg of solid
waste (olive cake or pomace) and variable quantities of liquid waste-
waters are produced. The volume of wastewaters could range from
40 to 100 L for every 100 kg of olives, depending on the oil-extraction
process used.
Pomace contains residue oil and so, it can be processed further to
extract “pomace oil” with husks or kernel wood as additional by-
products.
Other olive mill by-products are the leaves, which represent 5 percent
of the weight of olives worked.
More diffused mechanical systems of olive oil extraction, shown
in Fig. 14.1, are the following: traditional press, two-phase, or three-
phase systems.

Olives
100 kg

Grinder

Thermomixer

Water (50% p/p)

Three-phase decanter
Press

Two-phase decanter
Olive cake or
pomace Pomace Oil Wastewater
40 kg 40 kg 18 kg 92 kg
Centrifugation Oil Pomace two-
18 kg phase 82 kg

Oil Wastewater
18 kg 42 kg
FIGURE 14.1 Mechanical extraction of olive oil: comparison among traditional
press, two-phase decanter, and three-phase decanter.