Olive Oil in the Ionian and Corfu

This an article I wrote for the Corfu Gazette - September 2016

The Island of Corfu is famous for its olives and olive oil. The Island has over four million olive trees, some are thought to be more than 500 years old.

The Corfu economy during the 400 year Venetian period was largely based on exporting local products. The most important of the agricultural products of Corfu was olive oil.

Groves of olive trees were planted throughout the island during the Venetian period as olive oil was important to Venice's economy. Although the production of it was successful, the Republic only allowed exportation to Venice.  Statistics for the years 1766-1770 indicate there were 1,905,917 olive trees on Corfu that flourished in Corfu's lush climate.

Olive oil in Greece, which dates back 4000 years, is globally acknowledged for its purity and exceptional taste. More than 80% of the Greek olive oil is extra virgin, which is the top-ranked classification category in the world. This constitutes Greece as the world’s largest producer of extra virgin olive oil.

The olive tree will tolerate poor, rocky soil and so thrives in the mountainous parts of Corfu which are otherwise unsuitable for crop planting, even though it yields more fruit in lowland sites. It will not tolerate frosts below - 7°C (18°F), prolonged cold weather or excessively high annual rainfall but needs a stable cycle of hot, dry summers, short, wet springs and autumns and mild winters, with plenty of sunshine throughout the year which suits the Corfu climate perfectly.

Olive trees flower at the end of the winter and in the spring and the fruit develops very slowly, turning from green to pink and purple and finally to black when fully ripe. The tree produces flowers and fruit on the previous year's wood, and a good year tends to be followed by a less fruitful one. Black olives are usually harvested from December until February, while green olives are picked earlier, beginning in November.

There is considerable variation in the times and techniques of harvesting. Growers in some groves allow the olives to fall off on to nets or on to cleared, prepared ground, while others beat or shake the fruit off the branches, with sticks and poles, rakes or mechanical shakers, or climb up ladders to pick them by hand before they are ripe enough to fall spontaneously.

The percentage of oil in the olive increases with ripeness, and oil pressed from ripe olives is golden, while less ripe olives tend to produce more peppery, pungent oils with a pronounced green colour. The age of the tree and the variety determine the yield. Immature trees up to twenty years old will produce far less than trees in their prime, with an age of thirty to over 100 years. Really ancient trees, over 150 years old, also yield little and have begun their slow decline into death.

Olives are pressed in a variety of ways. Small communal mills in remote villages will press an individual's sackful of olives from a handful of privately owned trees, together with everyone else's, while, at the other end of the scale, the large industrial producers press vast quantities with using the latest stainless steel mills and centrifuges. At one time even the smallest villages had their own stone mills. In some Greek tavernas you may stumble across a large, circular stone receptacle where once olives were crushed. Ancient or modern, the process of oil extraction is essentially a simple one, involving up to five main stages: washing; crushing; grinding; pressing; and decanting or other­wise separating the oil from the water.

First the olives are brought in and weighed, usually in a receiving area where they can be checked for condition and sorted. Any leaves and twigs mixed in to them will be removed. Olives must be processed very soon after delivery to the mill, before the fermentation process begins.  Olives are then washed in cold water, drained, and then crushed to release the oil. This can be done by traditional methods, with mechanical rollers, or in modern, stainless steel crushers which work by simultaneously cutting, shearing and rubbing. Then they are ground into a smooth paste, stones and all.

Traditionally, the paste is now spread out on to natural fibre mats which will be stacked layer upon layer in a vertical press to extract, with relatively little pressure, what is known as the first cold pressing of oil. Alternatively, the oil can be extracted in a continuous centrifuge.

If a modern centrifuge is used for oil extraction, the paste produced by milling and crushing is fed into the machine, which spins at high velocity to separate the oil from the pulp. The oil emerging from press or centrifuge is actually a reddish mixture of oil, vegetable matter and water. This can be decanted manually or put into another centrifuge to separate the oil from the water.

The unfiltered oil is then stored in large containers. The ratio of olives to oil is approximately five kilos of fruit to each litre of oil. This oil can be filtered, to remove the sediment, or left to rest so that the sediment can naturally fall with gravity to accumulate at the bottom of the storage containers as the temperature rises in the spring. 

Either way, this is 'virgin' olive oil. To be labelled 'extra virgin, oil must have an acidity of 0.2-1 per cent. 'Olive oil' should not exceed 1.5-2 per cent of acidity.

This virgin and extra virgin olive oil can be purchased all over Corfu in the supermarkets and gift stores so make sure you treat yourself to some local produce while you are on the island and we are sure you will not be disappointed.