increase of the paste temperature, due to friction phenomena. They have the disadvantage of lower yield. It should be also noted that the stone mill is a discontinuous
system, while the metallic crusher systems are continuous and therefore their
performance in terms of processed olive is much higher.
VOO obtained with stone crusher is more aromatic and harmonic than oils
obtained using the other two types of crushers. The disc crusher, however, leads to
the formation of oil richer in phenolic compounds, more bitter and more stable to
lipid oxidation over storage (Angerosa and Di Giacinto 1995).
Stone mill can lead to higher concentration of volatile compounds than metallic
crushers, e.g. trans-2-hexenal, hexanal and cis-3-hexenol. For cv. Coratina and
Oliarola, Servili et al. (2003) reported that disc crusher caused higher concentrations
of C6 aldehydes and some esters such as hexyl acetate, 3-hexenyl acetate and cis-4hexenyl acetate than hammer crusher.
Olive stoning and other challenges for the development of new crushing systems
to reduce undesirable oxidation reactions and minimise enzymatic reactions have
been reviewed by Clodoveo et al. (2015) and Veneziani et al. (2016).
9.3.3.2 Malaxation and Extraction
Malaxation is a fundamental stage in VOO extraction, as it influences its yield and
composition and sensory profile of the product. It involves the continuous slow
mixing of the olive paste. Malaxation time and temperature are parameters that are
usually controlled by the industry during the VOO extraction process (Kalua et al.
2007; Clodoveo et al. 2015; Veneziani et al. 2016).
Malaxation time has been reported to be positively correlated to the total content
of volatile compounds, but negatively correlated with the concentration of total
phenolics (Ranalli et al. 2001). Longer malaxation times promote the accumulation
of alcohols and C5 compounds, particularly hexanal. The temperature increase
speeds up the activity of oxidative enzymes such as polyphenol oxidase,
lipoxygenase and peroxidase (Angerosa 2002).
There is a loss of volatile compounds when high malaxation temperatures are
applied, attributed to the enzyme’s deactivation, especially of hydroperoxide lyase
(Sánchez and Harwood 2002). This causes a considerable decrease of C6 compounds, cis-3-hexenol and C5 metabolites, as well as an increase in hexanol and
trans-2-hexen-1-ol and a loss of the bitter-pungent notes (Angerosa et al. 2000).
Angerosa et al. (2000) studied the combined effect of malaxation temperature and
time on the VOO aroma from cv. Coratina and Frantoio. They reported that
malaxation negatively affects the total amount of secoiridoids. Some phenolic
compounds, such as tyrosol, seem to undergo minor changes as affected by the
malaxation time, but they are only affected by the temperature. The opposite trend
was reported for the phenolic compound 3,4-dihydroxyphenylethanol-elenolic acid
dialdehyde (3,4-DHPEA-DEDA), for which the maximum concentration was
obtained at shorter malaxation time. The loss of phenolic compounds during
9 Olive (Olea europaea)
227
system, while the metallic crusher systems are continuous and therefore their
performance in terms of processed olive is much higher.
VOO obtained with stone crusher is more aromatic and harmonic than oils
obtained using the other two types of crushers. The disc crusher, however, leads to
the formation of oil richer in phenolic compounds, more bitter and more stable to
lipid oxidation over storage (Angerosa and Di Giacinto 1995).
Stone mill can lead to higher concentration of volatile compounds than metallic
crushers, e.g. trans-2-hexenal, hexanal and cis-3-hexenol. For cv. Coratina and
Oliarola, Servili et al. (2003) reported that disc crusher caused higher concentrations
of C6 aldehydes and some esters such as hexyl acetate, 3-hexenyl acetate and cis-4hexenyl acetate than hammer crusher.
Olive stoning and other challenges for the development of new crushing systems
to reduce undesirable oxidation reactions and minimise enzymatic reactions have
been reviewed by Clodoveo et al. (2015) and Veneziani et al. (2016).
9.3.3.2 Malaxation and Extraction
Malaxation is a fundamental stage in VOO extraction, as it influences its yield and
composition and sensory profile of the product. It involves the continuous slow
mixing of the olive paste. Malaxation time and temperature are parameters that are
usually controlled by the industry during the VOO extraction process (Kalua et al.
2007; Clodoveo et al. 2015; Veneziani et al. 2016).
Malaxation time has been reported to be positively correlated to the total content
of volatile compounds, but negatively correlated with the concentration of total
phenolics (Ranalli et al. 2001). Longer malaxation times promote the accumulation
of alcohols and C5 compounds, particularly hexanal. The temperature increase
speeds up the activity of oxidative enzymes such as polyphenol oxidase,
lipoxygenase and peroxidase (Angerosa 2002).
There is a loss of volatile compounds when high malaxation temperatures are
applied, attributed to the enzyme’s deactivation, especially of hydroperoxide lyase
(Sánchez and Harwood 2002). This causes a considerable decrease of C6 compounds, cis-3-hexenol and C5 metabolites, as well as an increase in hexanol and
trans-2-hexen-1-ol and a loss of the bitter-pungent notes (Angerosa et al. 2000).
Angerosa et al. (2000) studied the combined effect of malaxation temperature and
time on the VOO aroma from cv. Coratina and Frantoio. They reported that
malaxation negatively affects the total amount of secoiridoids. Some phenolic
compounds, such as tyrosol, seem to undergo minor changes as affected by the
malaxation time, but they are only affected by the temperature. The opposite trend
was reported for the phenolic compound 3,4-dihydroxyphenylethanol-elenolic acid
dialdehyde (3,4-DHPEA-DEDA), for which the maximum concentration was
obtained at shorter malaxation time. The loss of phenolic compounds during
9 Olive (Olea europaea)
227