malaxation is due to the enzymatic oxidation of the secoiridoid derivatives, catalysed
by polyphenol oxidase and peroxidase (Servili et al. 2008).
The hydrolysis of complex phenols (oleuropein, dimethyl oleuropein, ligstroside,
verbascoside, rutin and luteolin-7-glucoside) is fostered by the endogenous glucosidase. The non-hydrolysed oleuropein has low partition index toward the resulting
aglycones, and simple phenols dissolve appreciably in the oil phase, while the
non-hydrolysed phenol glycosides are more hydrophilic (Rodis et al. 2002).
The following compounds were proposed as markers for malaxation temperature:
1-penten-3-ol, cis-3-hexenal and octane, useful to differentiate malaxation temperatures of 15, 30 and 35
C, respectively (Kalua et al. 2006).
The oxygen concentration in the paste headspace during malaxation can be
manipulated to achieve significant modification of the VOO aroma, in relation to
the desired characteristics and industrial needs (Servili et al. 2008).
The separation of the liquid phase and solid particles from the olive paste is
usually performed using two major systems, pressure and centrifugation. The subsequent step involves the separation of the oil from the oil-water mixture, which is
done by centrifugation.
When separation systems based on pressure are applied, VOOs tend to be fruitier
and with a higher concentration of volatile alcohols, but possible fermentation and/or
degradation phenomena can take place, with the consequent appearance of sensory
defects (Angerosa 2002).
Differences in phenolic content in the oils were also observed between the
conventional centrifugal (“three-phase”) and the “two-phase”. The latter does not
involve the addition of water (except in very small amounts), which results in a lower
loss of hydrophilic phenolic compounds, particularly ortho-diphenols.
The use of two-phase centrifuge, compared to the three-phase one, allows the
production of VOOs with higher concentrations of trans-2-hexenal and greater total
aromatic content, but with lower concentration of pigments, aliphatic and triterpene
alcohols, sterols and waxes (Aparicio and Luna 2002).
The use of the three-phase centrifuge causes decrease in the content of C6
aldehydes, hexanol and trans-2-hexenol compared with the pressure extraction,
probably because of the addition of hot water (Angerosa et al. 2004). Incorrect or
improper management of the pressure extraction system may lead to olive paste
fermentation and the subsequent formation of off-flavours.
9.3.3.3 Olive Oil Filtration and Storage
VOO filtration may have important effects on the product sensory properties and
shelf life. Unfiltered oils are in an emulsion-dispersion form and contain a certain
amount of water (from 2 to 4 g/kg).
It has been recently reported that the industrial-scale filtration of highly bitterpungent extra VOO has an influence on the release of key aroma compounds, and
therefore filtration should be regarded as one of the possible parameters that can
potentially affect VOO phenolic composition. A significantly lower content of
228
N. Caporaso and D. Boskou
by polyphenol oxidase and peroxidase (Servili et al. 2008).
The hydrolysis of complex phenols (oleuropein, dimethyl oleuropein, ligstroside,
verbascoside, rutin and luteolin-7-glucoside) is fostered by the endogenous glucosidase. The non-hydrolysed oleuropein has low partition index toward the resulting
aglycones, and simple phenols dissolve appreciably in the oil phase, while the
non-hydrolysed phenol glycosides are more hydrophilic (Rodis et al. 2002).
The following compounds were proposed as markers for malaxation temperature:
1-penten-3-ol, cis-3-hexenal and octane, useful to differentiate malaxation temperatures of 15, 30 and 35
C, respectively (Kalua et al. 2006).
The oxygen concentration in the paste headspace during malaxation can be
manipulated to achieve significant modification of the VOO aroma, in relation to
the desired characteristics and industrial needs (Servili et al. 2008).
The separation of the liquid phase and solid particles from the olive paste is
usually performed using two major systems, pressure and centrifugation. The subsequent step involves the separation of the oil from the oil-water mixture, which is
done by centrifugation.
When separation systems based on pressure are applied, VOOs tend to be fruitier
and with a higher concentration of volatile alcohols, but possible fermentation and/or
degradation phenomena can take place, with the consequent appearance of sensory
defects (Angerosa 2002).
Differences in phenolic content in the oils were also observed between the
conventional centrifugal (“three-phase”) and the “two-phase”. The latter does not
involve the addition of water (except in very small amounts), which results in a lower
loss of hydrophilic phenolic compounds, particularly ortho-diphenols.
The use of two-phase centrifuge, compared to the three-phase one, allows the
production of VOOs with higher concentrations of trans-2-hexenal and greater total
aromatic content, but with lower concentration of pigments, aliphatic and triterpene
alcohols, sterols and waxes (Aparicio and Luna 2002).
The use of the three-phase centrifuge causes decrease in the content of C6
aldehydes, hexanol and trans-2-hexenol compared with the pressure extraction,
probably because of the addition of hot water (Angerosa et al. 2004). Incorrect or
improper management of the pressure extraction system may lead to olive paste
fermentation and the subsequent formation of off-flavours.
9.3.3.3 Olive Oil Filtration and Storage
VOO filtration may have important effects on the product sensory properties and
shelf life. Unfiltered oils are in an emulsion-dispersion form and contain a certain
amount of water (from 2 to 4 g/kg).
It has been recently reported that the industrial-scale filtration of highly bitterpungent extra VOO has an influence on the release of key aroma compounds, and
therefore filtration should be regarded as one of the possible parameters that can
potentially affect VOO phenolic composition. A significantly lower content of
228
N. Caporaso and D. Boskou