Most of the recent technological innovations applied to the mechanical
oil extraction process are aimed at improving virgin olive oil quality
and yield. Extra virgin olive oil (EVOO) quality is mainly based on the
qualitative/quantitative composition of monounsaturated fatty acids,
volatile and phenolic compounds that are strictly related to the health
and sensory properties of the product, with particular attention given
to the fraction of secoiridoid derivatives and C5 and C6
volatile compounds. The different levels of concentration of these
compounds are due to some important variables: agronomic and
technological. The chapter explains the recent approaches and
innovations introduced in the oil extraction process to improve the
working efficiency of the production system and to obtain high‐quality
extra virgin olive oils.
Extra virgin olive oil (EVOO) is the main source of lipids in
the Mediterranean diet. The marketable, healthy, and sensory quality of
an EVOO has been ascribed to the presence of bioactive components such
as monounsaturated and polyunsaturated fatty acids (MUFAs and PUFAs),
squalene, phytosterols, phenolic, and volatile compounds [1–5].
Several factors such as the genetic and geographical origin of the
olive fruit as well as agronomic practices and technological strategies
affect the phenolic content and aromatic profile of EVOO.
EVOO, and the by‐products of the mechanical extraction system such as
olive vegetation water and pomace contain several phenolic compounds
with recognized biological and health properties. These substances are
considered the principal bioactive compounds of EVOO, showing a high
antioxidant activity with an important role in the ratio between EVOO
consumption and chronic degenerative events, mainly inflammatory and
age‐dependent diseases such as cardio‐brain‐vascular diseases and cancer
Major phenolic compounds found in EVOO are phenolic acids, phenolic alcohols such as tyrosol (p‐HPEA)
and hydroxytyrosol (3,4‐DHPEA), hydroxy‐isocromans, flavonoids,
lignans, and secoiridoids. This latter class of compounds is represented
by the dialdehydic form of decarboxymethyl elenolic acid linked to
3,4‐DHPEA or p‐HPEA (3,4‐DHPEA‐EDA or p‐HPEA‐EDA), an isomer of oleuropein aglycon (3,4‐DHPEA‐EA) and the ligstroside aglycon (p‐HPEA‐EA).
They arise from the secoiridoid glycosides (oleuropein,
demethyloleuropein, and ligstroside) through the enzymatic action of
β‐glucosidase during the mechanical extraction process. Secoiridoids are
exclusive compounds of olive leaves, fruits, EVOO, and milling
by‐products (olive vegetation water and pomace). The secoiridoid
derivatives, along with lignans ((+)‐1‐acetoxypinoresinol and
(+)‐1‐pinoresinol), are the most abundant hydrophilic phenols of EVOO [6, 12, 13].
geographical and genetic origin of olive fruits, the choice of
agronomic practices, and the technological conditions of EVOO production
affect the wide variability in its phenolic and volatile composition
and, therefore, its healthy and sensory quality. The variability range
of the content of total phenols and oleuropein derivatives in over 700
industrial EVOO samples analyzed is illustrated in the box and whiskers
plots of Figure 1.
Based on these results, the contents of the total phenols and
oleuropein derivatives show a median of 534 and 398 mg/kg, with values
ranging between 187–997 and 77–112 mg/kg, respectively .
effects and organoleptic properties of EVOO have been mainly ascribed
to its phenols content (hydroxytyrosol and secoiridoids, in particular) [5, 15].
Several epidemiological studies have in fact fully demonstrated the
inflammatory, antioxidant, antimicrobial, anti‐proliferative,
antiarrhythmic, platelet antiaggregant and vasodilatory effects of EVOO
phenolic compounds [4–6].
Furthermore, based on scientific evidence, Regulation (EU) No 432/2012
granted the health claim to the EVOO polyphenols, fixing the quantity of
5 mg as the daily amount of hydroxytyrosol and its derivatives (e.g.
oleuropein complex and tyrosol) that should be ingested, with a moderate
consumption of olive oil (20 g/day) to reduce cardiovascular disease .
has been clearly known that phenolic compounds also have antioxidant
activity; therefore, they play a pivotal role in the prolonging of EVOO
shelf life .
Furthermore, from a sensory perspective, EVOO phenols are the compounds
responsible for the characteristic notes of “bitterness” and
“pungency”. They stimulate the receptors of taste and the free endings
of trigeminal nerve, which elicit the former the bitterness perception,
the latter pungency and astringency interaction .
Another important part of EVOO flavor is characterized by
many different olfactory notes, such as “cut grass,” “floral,” “green
apple,” “tomato” and “almond,” which are often related to many volatile
substances such as aldehydes, alcohols, esters, and hydrocarbons. In
particular, C6 and C5 compounds, especially C6
linear unsaturated and saturated aldehydes, alcohols, and esters,
represent the key odorants responsible for those perceptions of positive
When the olive is intact, the concentration of those volatile compounds
is still low. They greatly increase when the cell structures rupture
during the mechanical extraction process and with the consecutive
activation of the lipoxygenase (LOX). The C6 and C5
compounds are synthesized from linoleic (LA) and linolenic (LnA) acids
by the enzymatic activities included in the lipoxygenase (LOX) pathway,
and their concentrations depend on the level and the activity of each
enzyme involved in this LOX pathway. Figure 2 depicts a schematic illustration of the LOX pathway, which was extensively studied and discussed [18, 19].
it is worth mentioning that even though the main pathways are known for
the formation of olive oil volatiles, the only correlation that has
been proved is that between the “cut grass” aroma and C5 and C6 aldehydes (saturated and unsaturated) [18, 20].
processing includes a series of mechanical operations for extracting
the oil from olive drupes by physical means only, according to
Regulation (EU) No 1348/2013 .
Among them, the most important as regards quality is the crushing of
the olives, which allows the release of the droplets of oil from the
vacuoles, breaking down the cellular structure of the olive fruit; the
malaxation of the olive paste, which promotes the coalescence of the oil
droplets, with the simultaneous release of phenolic compounds into the
oil phase and the increase of EVOO aroma; the mechanical recovery of the
oil by centrifugation (continuous process) or pressing (discontinuous
process); and lastly, filtration, used for removing suspended particles
and eliminating residual water responsible for EVOO oxidation and the
onset of off‐flavors during its shelf life.
have been already developed during the last 10 years in order to
optimize all the mechanical extraction steps that play a crucial role in
the qualitative/quantitative composition of phenolic and volatile
profile and, consequently, the sensory characteristics of the resulting
EVOOs. Technological innovations have led to new extraction plants
designed to improve the quality of oils obtained from olives with
different genetic, geographical, and agronomic characteristics. More