Greek teacher

The more gnarled the more yield you get

Olive trees have to be able to take a load

Olive tree with potatoes as an undercrop

A centrifuge seperates oil, cores and water

Production of olive oil

History

In former times they used water or muscle power from animals and people to get oil and electricity. One big problem of water power was that the water stream was not constant. The water of the snowmelt took a lot of stones in the valley and the work at the driving gear was very dangerous. The work was also hard, because the employees had to stay in the factory from December to March.

But how did they process the olives? First they put the olives in the so called “ALONI” which is a huge bowl where two big marble stones rotated because of the water power. This process broke the fruits to a juicy paste. Next the paste was put into big bags made of goat-hair which operated as a filter in the pressing process. Quite all solid components were separated and used for heating or producing soaps. The liquid mixture was poured into big tanks. There the oil separated from the water and some solid components because of the specific gravity. After two hours the oil swam on the topside so that they could skim it. To get best quality the oil was centrifuged.

This olive oil was processed nature-related and was healthier because it was cold pressed.

Olive trees

The whole process begins with a wild olive fruit and a bird. The bird eats the olive together with the core. The acids in the stomach destroy the fat round the core, so that it is fertile. When the core reaches the soil a wild olive tree begins to grow. The farmer digs out the young plants. A different opinion is to grow scions. This is what most of the farmers do, because the young plants are clones and have all the good (and bad) properties from the mother-plant. When the tree is big enough it is grafted. Five to six years after the graft the farmer gets the first harvest.

Harvest

Before harvesting they put a huge net on the ground under the trees. Either they have a machine which shakes the trees or they shake the branches with long sticks. Then the olives are collected. Some sorts are picked by hand
After the first harvest most of the tree is cut back. The next year the tree has no significant amount to harvest. But every second year there are many olives. This phenomenon is called alternation. After the harvest the tree is cut again so that the branches get turbid and able to take a load. The tree should stay tiny and easy to harvest. The only disadvantage is that the tree has no yield the next year, because it needs the energy for growing (alternation). The more it is gnarled the more olives you get.

Oil factory

From November till February the oil farmer brings the olives from the orchard to a factory. The olives from one farmer are put in a machine where the leaves and branches are blown away. The second step is a machine which washes the olives with cold water. After that the olives are weighed. The following machine cuts the olives into little pieces. The juicy paste is mixed for one hour at a temperature below 35°C. The olives from every farmer are separately mixed. The 6th machine is a centrifuge which separates the water (30%), the oil and the cores from the rest. The oil is still mixed with some water, so you need a second centrifuge to get pure olive oil.

The cores can be used for fertilizing or for producing industrial oil, the rest is used for HEATING.

Quality

A consequence of the late harvest in November is that there could be frozen olives. They are separated from the others and processed to lower quality oil, it contains bitter flavours, after some days of defrosting.

The quality of the oil also depends on the natural conditions. The mountain area is better because the soil is more fertile and the temperature is lower than in valleys. The trees get more water, they produce bigger olives, which contain 30 to 40 % of oil. In lower areas you hardly get more than 20% of oil out of the fruits.

Growing different varieties suitable to the regional conditions cause either more or less yield.

The quality determines the price for selling.

Pests and diseases

• Olive fruit fly: The olive fruit fly is the most feared pest at the olive plantations, they lay their eggs in the ripening fruits. The grubs addle the fruit. Besides they transfuse tubercle.
• Trunk decay: It is a fungus, which decays the trunk by and by. Most times the farmers cut out the pertained parts, but this promotes the infection of the healthy parts.
• Tubercle: Is a bacterium, which causes proliferations and a dying of branches. This reduces the yield. The bacteria is transfused by the olive fruit fly.
• Black scale: An infection which reduces the harvest.
• Greenfly: An infection in spring can cause atrophy of young shoots, leaves and blossoms. So you get fewer yields.
  

Combined area use

Sometimes farmers use the olive orchard also as a field for potatoes. The only advantage of this is that you get a little more money out of your orchard, if you sell the potatoes. One of the disadvantages is that potatoes promote the growing of fungal infections which can overlap to the trees. The potatoes are the foundation for the fungus to survive. The best treatment against the infection is that the farmer fertilizes hay and less nitrate.
Instead of mowing the grass under the olive trees farmers use sheep and goats. Young trees have to be fenced otherwise the goats would eat the leaves.  After cutting the tree back these animals are useful because they love to eat the leaves from the left branches.

Facts

• Spain, Italy and Greece produce most olive oil
• Greece: 2 300 000 tonns of olives
• 2 400 000kg olive oil
• Average yield 50-70kg per tree
• Fluctuating oil content: 15-40%
• 97,5 mio olive trees in Greece
• 150- 200 trees per hectar

Back to Olive oil / Regional products

Page updated 30.3.2007