However, sensory notes other than the “fruity”, “pungent” and “bitter” that are
assessed during the panel test for olive oil classification are not official, and they
are not required for assessing the market category of the olive oil. In particular cases,
the presence of peculiar sensory notes at a certain level of intensity is required for
some extra virgin olive oils with Product Designation of Origin (PDO) labels. A
PDO product has to provide distinctive characteristics from a sensory point of view
in addition to providing evidence related to the history of the product (tradition) and
the link between the people of a particular area and the product. In this case, the
regulations for PDO products make it compulsory to perform sensory analysis to
assess the presence and intensity of particular sensory descriptors, e.g. “tomato”,
“tomato leaves”, “artichoke”, “rosemary”, “almond”, etc.
Several hundreds of volatile compounds have been reported in olive oils, especially in VOOs. Aldehydes and C6 alcohols have been related to positive sensory
attributes, and to the note of “sweetness”, which is just the aroma recalling sweet
attributes but does not refer to an actual taste sensation. The odour threshold of
volatile compounds is dramatically different depending on the chemical structure
and physico-chemical characteristics of each molecule. For example, cis-3-hexenal,
which gives the typical odour of freshly cut grass and despite its low concentration,
greatly contributes to the aroma as it has a very low odour threshold. On the contrary,
trans-2-hexenal has much higher perception threshold, and it contributes minimally
to the final VOO aroma, although it is the most abundant volatile compound in the
oil (Kalua et al. 2007).
Trans-2-hexenal and trans-2-hexenol have been associated with VOOs obtained
from olives in good conditions. The following compounds contribute mostly to the
“green note”: cis-3-hexenal, cis-3-hexenol (grass and banana) and cis-3-hexenyl
acetate (fruity and green leaves). Important in defining the complex flavour are
also trans-2-hexenal, hexanol and trans-3-hexenol. Hexyl acetate contributes to
perceptions of fruity and sweet, while hexanal is responsible for the “green” and
apple note.
Cis-3-hexenol has been associated with the bitter note of VOOs, as well as the
attributes of “apple”, “tomato”, “vegetable bitter”, “grass” and “fruity olive oil”,
along with some C5 alcohols (cis-2-penten-1-ol and 1-penten-3-ol) and trans-2hexenal (Caporale et al. 2004). Other compounds such as toluene, octane, octene and
3-methyl butanol arise from different routes from the LOX pathway and are not
related to positive sensory attributes of VOO. The “fruity” note of VOO was found
to be positively correlated with the cis-3-hexenol and negatively correlated with
3-pentanone. The “ripe fruit” sensory note is correlated with 3-pentanone, while
“leaf” is positively correlated with hexyl acetate, 1-penten-3-ol and cis-2-penten-1-ol
and negatively correlated with hexanol, associated with the “grass” note. The note of
“almond” positively correlates with the hexyl acetate, 1-penten-3-ol and cis-2penten-1-ol and negatively with the hexanol; cis-3-hexenol correlates positively
with the scent of “tomato” and “bitter vegetable”; 3-pentanone correlates negatively
with the attributes of “bitter”, “spicy”, “tomato” and “vegetable bitter”. The attributes of bitter and spicy oil are due to the presence of phenolic compounds. The
bitter taste is attributed to aglycones of the dialdehydic form of the decarboxymethyl
9 Olive (Olea europaea)
237
assessed during the panel test for olive oil classification are not official, and they
are not required for assessing the market category of the olive oil. In particular cases,
the presence of peculiar sensory notes at a certain level of intensity is required for
some extra virgin olive oils with Product Designation of Origin (PDO) labels. A
PDO product has to provide distinctive characteristics from a sensory point of view
in addition to providing evidence related to the history of the product (tradition) and
the link between the people of a particular area and the product. In this case, the
regulations for PDO products make it compulsory to perform sensory analysis to
assess the presence and intensity of particular sensory descriptors, e.g. “tomato”,
“tomato leaves”, “artichoke”, “rosemary”, “almond”, etc.
Several hundreds of volatile compounds have been reported in olive oils, especially in VOOs. Aldehydes and C6 alcohols have been related to positive sensory
attributes, and to the note of “sweetness”, which is just the aroma recalling sweet
attributes but does not refer to an actual taste sensation. The odour threshold of
volatile compounds is dramatically different depending on the chemical structure
and physico-chemical characteristics of each molecule. For example, cis-3-hexenal,
which gives the typical odour of freshly cut grass and despite its low concentration,
greatly contributes to the aroma as it has a very low odour threshold. On the contrary,
trans-2-hexenal has much higher perception threshold, and it contributes minimally
to the final VOO aroma, although it is the most abundant volatile compound in the
oil (Kalua et al. 2007).
Trans-2-hexenal and trans-2-hexenol have been associated with VOOs obtained
from olives in good conditions. The following compounds contribute mostly to the
“green note”: cis-3-hexenal, cis-3-hexenol (grass and banana) and cis-3-hexenyl
acetate (fruity and green leaves). Important in defining the complex flavour are
also trans-2-hexenal, hexanol and trans-3-hexenol. Hexyl acetate contributes to
perceptions of fruity and sweet, while hexanal is responsible for the “green” and
apple note.
Cis-3-hexenol has been associated with the bitter note of VOOs, as well as the
attributes of “apple”, “tomato”, “vegetable bitter”, “grass” and “fruity olive oil”,
along with some C5 alcohols (cis-2-penten-1-ol and 1-penten-3-ol) and trans-2hexenal (Caporale et al. 2004). Other compounds such as toluene, octane, octene and
3-methyl butanol arise from different routes from the LOX pathway and are not
related to positive sensory attributes of VOO. The “fruity” note of VOO was found
to be positively correlated with the cis-3-hexenol and negatively correlated with
3-pentanone. The “ripe fruit” sensory note is correlated with 3-pentanone, while
“leaf” is positively correlated with hexyl acetate, 1-penten-3-ol and cis-2-penten-1-ol
and negatively correlated with hexanol, associated with the “grass” note. The note of
“almond” positively correlates with the hexyl acetate, 1-penten-3-ol and cis-2penten-1-ol and negatively with the hexanol; cis-3-hexenol correlates positively
with the scent of “tomato” and “bitter vegetable”; 3-pentanone correlates negatively
with the attributes of “bitter”, “spicy”, “tomato” and “vegetable bitter”. The attributes of bitter and spicy oil are due to the presence of phenolic compounds. The
bitter taste is attributed to aglycones of the dialdehydic form of the decarboxymethyl
9 Olive (Olea europaea)
237