Many don't know it but most of the characteristics of extra-virgin olive oil depend on the stage of ripeness at which the olives are harvested.
The olives ripen between the end of September and the end of December. This can be seen in their colour, which changes from green to purple and finally to black.
Green and young olives produce an intense green, fragrant and pungent oil. Their yield is low, in the order of 9-10% (i.e. 9-10 litres of oil produced per 100 kg of ground olives).
Black, over-ripe olives produce a yellow, rancid oil. Their yield is high, around 25-30% (25-30 litres of oil produced per 100 kg of olives).
A quality extra-virgin olive oil is produced from olives harvested early, generally speaking in October.
A quality extra-virgin olive oil has an intense smell, which is a sign of the high content of polyphenols and oleic acid.
Polyphenols are the substances that give e.v.o. oil its unmistakable smell of fresh fruitiness, reminiscent of field grass and artichokes. These substances are also natural antioxidants that have strong anti-carcinogenic properties and also help reduce the risk of heart disease.
A daily intake of at least 20g of quality e.v.o. oil has been shown to help protect blood lipids from oxidative stress (EU Reg. 432/2012).
Extra-virgin olive oil's age is also decisive for its quality.
Here the saying "vino vecchio, olio nuovo" applies, i.e. new oil is good oil.
A freshly pressed extra-virgin olive oil is of highest quality as it is still loaded with all those flavours and scents lent by the polyphenols.
As time goes by the polyphenols (which are volatile substances) decay and as they disappear the quality of the e.v.o. oil progressively deteriorates.
An e.v.o. oil that is two years old has generally lost its nutritional qualities and is no longer suitable for consumption (although not being harmful).
It is therefore recommended when buying extra-virgin olive oil to check out the harvesting year on the label, and to make sure that the e.v.o. oil has been produced from olives harvested in the most recent harvesting year.