Let us introduce the various harvesting methods:
OLIVE HARVEST BY HAND
With this method, the olives are literally picked from the tree by hand or streaked from the branches of the olive trees and collected in a kind of „shoulder bag“. Sometimes smaller tools such as e.g. small rakes are used. This is surely the most gentle method for the trees and the olives, since neither of them suffer any injuries. Mostly only quality producers use this method or when the olives are being collected for food purposes rather than oil.
Olive oil: the gold of Crete.
HARVESTING OF OLIVES WITH PNEUMATIC COMBS OR „VIBROLI“
In recent years, quality producers started using mechanical devices such as pneumatic combs or the so-called „vibroli“ (a kind of stick with about 20 centimeter combs on it). They support the manual harvester and do not damage the olive tree or the olives. This method is very helpful and accelerates the harvesting process – but, of course, is still hard work.
OLIVE HARVESTING WITH SHAKERS
For some years now, so-called “vibrators”, which are mounted on tractors, have been used to harvest the olives. The olives are “shaken” from the tree with a shaker that grips the trunk with a pair of pliers. The olives falling from the trees get caught in nets or tarpaulins stretched underneath. The disadvantage of this harvesting method is that it cannot be used in slope terrains. In addition, some some sorts of olives cannot be shaken from the tree by this method. The advantage of this method is that the olives remain undamaged. The disadvantage is, that if olives are first shaken from the tree and then some time later picked up, they start to rot on the ground relatively quickly or absorb substances that negatively affect the taste.
Harvesting olives: A lot of manual work.
“HARVEST” FROM THE GROUND
The least suitable method for obtaining high-quality olive oil is to leave the olives hanging on the tree until they fall – overripe – into the nets stretched on the ground underneath the trees, from where they are manually picked up. The overripe olives have long passed their ideal harvest time. Studies show that a mixture of only 5% of olives picked from the ground with fresh olives from the tree has an adverse effect on the quality of the oil that the “extra virgin” quality class can often no longer be achieved.
HARVESTING OLIVES BY „DEPOSIT“
A traditional way of harvesting is to knock down the olives with long bamboo or cypress wood sticks. However, this way olives can only be harvested when the olives are already very ripe and therefore fall off easily.
Once beaten down from the tree, the olives get separated from branches and leaves are put into a kind of sieve, filled into sacks or boxes and taken to the next olive press. Mainly the olive tree, but also the olives can be injured with this method negatively impacting the oil quality. Since this method is carried out manually, the harvest yield per person is relatively low. Additionally, it is quite tedious and results in great physical stress.
Of course, the time of the olive harvest is very important.
Since the ripeness of the olives significantly influences the intensity of the taste as well as the yield, the time for harvesting is one of the most important factors in producing high quality olive oil. Olive oil tastes all the more intense and hotter the sooner – i.e. greener – the olives are harvested. The content of valuable, health-promoting substances tends to be higher in early harvested olive oils.
Harvesting olives and everyone helps.
The later, i.e. the blacker, the olives are harvested, the milder the olive oil obtained. In order to determine the ideal time, some quality producers use chemical analyzes which provide information about the sugar content in the olives and the enzymatic activity, which if possible should be low.
The quantity or yield of late harvesting is usually higher, since these olives have a higher oil content. The content of valuable ingredients – such as antioxidants – is relatively low.
The ripeness of the olives – green, reddish purple and black – depends on the sort of olives, temperatures, hours of sunshine and irrigation.
1.) Green (immature): Green olives are still immature. Extracting olive oil from green fruits takes more efforts and means less yield. This automatically makes the “green” oil more expensive. Olive oil obtained from green olives also tastes „green“, i.e. rather bitter (one of the three positive characteristics of an oil) and a little bit like grass with the unripe fruit note resulting in special freshness. These oils contain a high proportion of polyphenols (antioxidant ingredients) responsible for the bitter taste which guarantee a long shelf life of the olive oil, since they work as natural preservatives. The chlorophyll content is also higher in green fruits, so that the oils have a more pronounced green color.
2.) Ripening: At the beginning of the ripening phase, olives first turn yellow-green, then reddish-purple and the fruits become softer. The olives still have a high polyphenol content, but slowly develop more mature flavors in addition to the bitterness, as well as a certain hotness (also one of the three positive features). The yield of olive oil from these fruits is much higher and processing is easier.
3.) Black (ripe): Ripe olives take on a black color, the polyphenol content is significantly lower than that of unripe fruits. Black olive oils are only slightly bitter and less spicy with a rather sweet note. The oil has a rather golden color (depending on the type of olive) and a much lower shelf life.
Transport of the olives.
Regardless of the ripeness – ideally olives are transported to the oil mill on the day of harvesting and processed the day after at the latest. If the time between harvesting and processing is too long, the same happens as does with fruit in the kitchen. Pressure marks turn brown and the fermentation process slowly begins to work. The fresh, crisp aroma is then quickly lost and the quality of the olive oil decreases.
Depending on the sort of olive, about five to ten kilograms of olives are needed for one liter of olive oil. A large old olive tree can easily deliver up to 180 kg of olives. On average, 50-70 kg of olives are harvested from an olive tree, i.e. a single tree produces about five to ten liters of oil per year.
So: 1 tree -> 50-70 kg of olives -> 5-10 liters of oil
And don’t be surprised if one liter of olive oil does not weigh one kilogram: olive oil has a density of about 0.91 g / cm3 under normal conditions (temperature 20 ° C, pressure 1013 mbar).
One liter of olive oil therefore weighs approximately 910 grams, but is still one liter!