subsequent studies, the same authors (Gomez-Rico et al. 2009) verified that the
hexanal concentration also shows an inverse correlation with increasing water
availability.
Opposite conclusions were reported by Stefanoudaki et al. (2009). Lower values
of 1-penten-3-ol and 1-penten-3-one were found as a result of the irrigation, for
cv. Leccino. A decrease of total volatile compounds was reported in irrigated olive
oils. The C5 compounds undergo a drastic decrease, but, in contrast to other authors,
no increases were reported in this study for C6 compounds.
The irrigation strategy has been reported to be more effective than the total
amount of rainfall during the year, as the concentration of phenolic compounds
depends on the water stress (Gomez-Rico et al. 2006; Stefanoudaki et al. 2009). Also
fatty acid composition undergoes modification, with an increase in the ratio of
monounsaturated to polyunsaturated fatty acids (Tognetti et al. 2007). The sensory
evaluation of VOOs from irrigated orchards seems to show lower intensity of the
attributes fruity, bitter and pungent (Stefanoudaki et al. 2009).
Montedoro et al. (1978) reported the possibility to discriminate VOOs from
different Italian regions through the analysis of volatile compounds. VOOs from
Italy were found to be richer in C6 aldehydes and lower in fruity esters than
Moroccan oils (Kalua et al. 2007).
9.3.3 Compositional Changes due to Processing
9.3.3.1 Harvesting Systems and Crushing
The olive harvesting system has a dramatic influence on the final flavour of VOO.
Oils obtained from olives picked from the soil are qualitatively poorer as shown by
the chemical parameters (acidity, peroxides, UV) and the organoleptic analysis. The
concentration of trans-2-hexenal and cis-3-hexenyl acetate (“green notes”) in the oil
decreases, while hydrocarbons, acetic acid and other carbonyl compounds are found
at higher concentrations when there is a longer contact of the olives with the soil
(Angerosa et al. 2004).
Mechanical harvesting of the olives has been reported to exert little influence on
the chemical composition of VOOs compared to manual harvest. Olive harvesting
needs to be performed in a way that damage of the fruit, spontaneous fermentation
and mould growth are avoided.
The majority of VOO aroma compounds are produced during and after the
crushing phase, when the enzymatic oxidation of linoleic and linolenic acid takes
place (Baccouri et al. 2008). The type of mill influences the final oil quality, by
changing the quali-quantitative composition of some minor constituents, with consequent influence on the organoleptic properties and product stability.
There are two major types or olive crushers: granite stone mill and metallic
crusher. This latter can be divided into two types, i.e. disc and hammer crushers.
The hammer crushers have stronger effects and cause a strong emulsification and an
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hexanal concentration also shows an inverse correlation with increasing water
availability.
Opposite conclusions were reported by Stefanoudaki et al. (2009). Lower values
of 1-penten-3-ol and 1-penten-3-one were found as a result of the irrigation, for
cv. Leccino. A decrease of total volatile compounds was reported in irrigated olive
oils. The C5 compounds undergo a drastic decrease, but, in contrast to other authors,
no increases were reported in this study for C6 compounds.
The irrigation strategy has been reported to be more effective than the total
amount of rainfall during the year, as the concentration of phenolic compounds
depends on the water stress (Gomez-Rico et al. 2006; Stefanoudaki et al. 2009). Also
fatty acid composition undergoes modification, with an increase in the ratio of
monounsaturated to polyunsaturated fatty acids (Tognetti et al. 2007). The sensory
evaluation of VOOs from irrigated orchards seems to show lower intensity of the
attributes fruity, bitter and pungent (Stefanoudaki et al. 2009).
Montedoro et al. (1978) reported the possibility to discriminate VOOs from
different Italian regions through the analysis of volatile compounds. VOOs from
Italy were found to be richer in C6 aldehydes and lower in fruity esters than
Moroccan oils (Kalua et al. 2007).
9.3.3 Compositional Changes due to Processing
9.3.3.1 Harvesting Systems and Crushing
The olive harvesting system has a dramatic influence on the final flavour of VOO.
Oils obtained from olives picked from the soil are qualitatively poorer as shown by
the chemical parameters (acidity, peroxides, UV) and the organoleptic analysis. The
concentration of trans-2-hexenal and cis-3-hexenyl acetate (“green notes”) in the oil
decreases, while hydrocarbons, acetic acid and other carbonyl compounds are found
at higher concentrations when there is a longer contact of the olives with the soil
(Angerosa et al. 2004).
Mechanical harvesting of the olives has been reported to exert little influence on
the chemical composition of VOOs compared to manual harvest. Olive harvesting
needs to be performed in a way that damage of the fruit, spontaneous fermentation
and mould growth are avoided.
The majority of VOO aroma compounds are produced during and after the
crushing phase, when the enzymatic oxidation of linoleic and linolenic acid takes
place (Baccouri et al. 2008). The type of mill influences the final oil quality, by
changing the quali-quantitative composition of some minor constituents, with consequent influence on the organoleptic properties and product stability.
There are two major types or olive crushers: granite stone mill and metallic
crusher. This latter can be divided into two types, i.e. disc and hammer crushers.
The hammer crushers have stronger effects and cause a strong emulsification and an
226
N. Caporaso and D. Boskou