9.6 Sensory Assessment and Volatile Compounds
The International Olive Council (IOC) is the intergovernmental organisation that
brings together olive oil and table olive producing and consuming stakeholders. Its
main mission is the harmonisation of rules and quality control among the olive oil
sector, also proposing new methods and limits to assure high quality for the olive
products and consumer protection. Its member states represent approximately 97%
of the olive oil producers worldwide. The IOC regulation regarding the classification, physico-chemical analyses and sensory assessment of olive oils is compulsorily
applied in the European Union, the world’s first olive oil producer, and in many
other countries.
Different from other food products, VOOs require compulsory sensory analysis.
This is done by approved sensory panels of at least eight expert assessors, trained to
describe and evaluate virgin olive oils based on a defined protocol and a quantitative
method in which assessors classify the presence and intensity of defects and positive
attributes (fruity, bitter, pungent). The training requirements, assessment protocol
and data analysis to be applied on the results are strictly regulated (IOC 2015b, c;
Reg. EU 1991 and its amendments). The visual appearance of olive oil is not a
quality parameter for market or trade, but—similar to other products—is important
for many consumers, as it gives a “first impression” about a food. However, this
impression is misleading as olive oil’s visual appearance has little relation with
quality. Similarly, fresh VOOs often have a green colour due to chlorophylls, which
degrade over storage to produce pheophytin and then chlorophyllides, with yellowbrown colour. The yellow colour of olive oils is due to carotenoids, which undergo
similar transformation during storage, but some carotenoids are more stable than
others.
The official method for VOO sensory assessment completely excludes any colour
evaluation as a quality indicator, and it emphasises the importance of flavour, i.e. the
combination of aroma and taste. The vocabulary for VOO evaluation is rather
limited, when the purposes is to assess its commercial category. This is mostly
related to the presence/absence of defects, which can fall into five categories, and
three positive attributes, which are “fruity”, “pungent”, and “bitter”. Few consumers
are used to vegetable oils that naturally possess bitter and pungent notes. Even in
producing countries, sometimes consumers tend to prefer “light” olive oils, i.e. those
with limited bitter-pungent notes and relatively low intensity of fruitless. However,
the current opinion is that consumers should be educated to positively evaluate more
pungent-bitter VOOs, as this is related to higher quality.
Sensory defects of VOOs have different origins. When olive fruits are not
processed within a limited period of time, often 12–24 h would be preferable—
and especially when the olives are amassed and aeration is not guaranteed—fermentation takes place during storage. This can lead to the generation of a series of
volatile compounds related to the aerobic or anaerobic fermentation. The first
phenomenon is observed mainly when the olives are stored for prolonged time
before processing, while the second one mainly occurs during the storage of the
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The International Olive Council (IOC) is the intergovernmental organisation that
brings together olive oil and table olive producing and consuming stakeholders. Its
main mission is the harmonisation of rules and quality control among the olive oil
sector, also proposing new methods and limits to assure high quality for the olive
products and consumer protection. Its member states represent approximately 97%
of the olive oil producers worldwide. The IOC regulation regarding the classification, physico-chemical analyses and sensory assessment of olive oils is compulsorily
applied in the European Union, the world’s first olive oil producer, and in many
other countries.
Different from other food products, VOOs require compulsory sensory analysis.
This is done by approved sensory panels of at least eight expert assessors, trained to
describe and evaluate virgin olive oils based on a defined protocol and a quantitative
method in which assessors classify the presence and intensity of defects and positive
attributes (fruity, bitter, pungent). The training requirements, assessment protocol
and data analysis to be applied on the results are strictly regulated (IOC 2015b, c;
Reg. EU 1991 and its amendments). The visual appearance of olive oil is not a
quality parameter for market or trade, but—similar to other products—is important
for many consumers, as it gives a “first impression” about a food. However, this
impression is misleading as olive oil’s visual appearance has little relation with
quality. Similarly, fresh VOOs often have a green colour due to chlorophylls, which
degrade over storage to produce pheophytin and then chlorophyllides, with yellowbrown colour. The yellow colour of olive oils is due to carotenoids, which undergo
similar transformation during storage, but some carotenoids are more stable than
others.
The official method for VOO sensory assessment completely excludes any colour
evaluation as a quality indicator, and it emphasises the importance of flavour, i.e. the
combination of aroma and taste. The vocabulary for VOO evaluation is rather
limited, when the purposes is to assess its commercial category. This is mostly
related to the presence/absence of defects, which can fall into five categories, and
three positive attributes, which are “fruity”, “pungent”, and “bitter”. Few consumers
are used to vegetable oils that naturally possess bitter and pungent notes. Even in
producing countries, sometimes consumers tend to prefer “light” olive oils, i.e. those
with limited bitter-pungent notes and relatively low intensity of fruitless. However,
the current opinion is that consumers should be educated to positively evaluate more
pungent-bitter VOOs, as this is related to higher quality.
Sensory defects of VOOs have different origins. When olive fruits are not
processed within a limited period of time, often 12–24 h would be preferable—
and especially when the olives are amassed and aeration is not guaranteed—fermentation takes place during storage. This can lead to the generation of a series of
volatile compounds related to the aerobic or anaerobic fermentation. The first
phenomenon is observed mainly when the olives are stored for prolonged time
before processing, while the second one mainly occurs during the storage of the
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