Following harvesting the olive fruit is transferred to the olive press where it undergoes various processes in order to extract the oil which its contains. The processes which take place at the olive press follow specific rules in order to achieve high quality.

Following many years of research and studies at local level, the factors and conditions which degrade quality at the olive press were defined and the rules which need to be followed at olive presses in order to avoid this quality degradation and to produce high quality olive oil were established.

The first process which the olives undergo at the olive press is temporary storage and placement of the sacks in small piles on pallets. This step is intended not only to facilitate movement but also to ventilate the olives and avoid fermentation. The piles which were formed in the past, and which continue to be formed in various states to this day, were proven following experiments conducted by the Institute, to be harmful for quality. The olives remain in this position for two days at most until they move on to be processed.

Processing commences with the olives passing through special machinery to clean them of leaves and wash them.

Leaves are removed using an automated defoliation device. This step is necessary because when a large quantity of leaves are ground up with the olives the olive oil takes on a bitter taste and absorbs chlorophyll (a green colorant) which does not help in preserving its quality.

This is followed by washing which removes foreign bodies (soil, dust) which are on the olives.

Grinding of the olives, in other words cutting them into small pieces, which form the well known olive paste, is an important phase in pressing.

Up until a few years ago the fruit was crushed in olive mills using 3 or 4 stones of various diameters.

In more recent years the crushing / grinding of the olives has been done using metal crushers which rotate the olives at great speed inside a pierced drum. During crushing care is required so that the temperature of the paste does not increase greatly and that the olives are not excessively crushed because that may result in the olive oil acquiring a bitter taste.

Kneading of the paste is done in special rounded or long kneaders. It is important that their walls be made of stainless steel and that the temperature of the paste should not exceed 30ο C. kneading should last around 30 - 45 minutes.

Extracting the olive oil from the olive paste can be done under pressure or centrifugally.

Pressure was the method used from ancient times until recently. The technology used in presses went through many stages, from the wooden hand operated presses of the Roman period they changed into metal, hydraulic, automated presses which were the main means for obtaining oil until 10 years ago. As a method pressing entails high labour costs and has certain disadvantages due to the fact that the pressing devices used cannot prevent small pieces of paste from one batch remaining in the press for the next batch, which contributes to an increase in acidity.

The centrifugal method is the one which has come to prevail recently and is 99% dominant on the island. This method uses special horizontal decanters which ensure automation and high cleanliness levels. These decanters are divided into 3 phase decanters which transform the paste into oil in three phases as well as liquid waste and solid waste (stones) with approximately 45% moisture. The disadvantage of these decanters is the production of large volume of waste (1:1 in relation to fruit).

Recently 2 phase decanters have been used which transform the paste in two phase, oil and solid waste (stones) which has the disadvantage of being very liquid (65% moisture) which is difficult to process in olive stone presses in order to extract oil from the stones. Nonetheless they have advantages since they produce a limited amount of liquid waste (0.2:1 in relation to fruit). Lately efforts have been made to introduce other intermediate types which produce olive stones with an intermediate moisture content.

Decanting and cleaning of the olive oil is done in special vertical decanters which remove water and other foreign bodies from the oil and help make it clear.

Storage

Natural, high quality virgin olive oil can be stored in an ideal state for a long period of time if kept under the same physical conditions when it was inside healthy olives.

Olive oil deteriorates when it is exposed to light, oxygen and high temperatures. For this reason it should be stored in containers which are airtight and in places where temperatures do not exceed 30οC.

Olive oil in large quantities is stored in large stainless steel tanks which are placed in suitable covered facilities so as to protect them from high temperatures. It remains in these tanks for some period of time until it turns clear thanks to natural settlement.

When olive oil is transported for retail sale and when stored in consumer's homes it must be kept in containers which do not let light and air in. dark glass bottles or stainless steel metal containers are considered to be the best. Clear plastic or glass bottles should be avoided and when used should be placed inside cardboard boxes. When olive oil is placed in clear glass containers in restaurants or homes and remains there for several days its characteristics may deteriorate and for this reason this should be avoided.