The first important step is the olive harvest. The way the olives are harvested and whether olives are injured during this step is among the first factors determining the quality of the olive oil to be processed. The traditional harvesting method, namely hitting the branches with sticks to make the olives fall of the trees, has been proven to injure the fruits and the tree, leaving the latter exposed to fungi and bacteria (which can penetrate its injuries). Carefully picking the olives is essential to ensure the quality of the final product. The commonest harvesting method is by using olive rakes or shaking the tree, so that the fruits fall on the nets without being injured. Workers should be careful and not step on the olives while walking on the nets. Olives should then be placed in plastic crates and not sacks (pressure can injure the fruits and the olive oil quality declines) and be transferred to the oil mill as soon as possible. At the next stage, the olives are separated from leaves and branches, washed and crushed. After the olives have been crushed, the olive paste is placed in the malaxator and kneaded for few minutes (usually not longer than 30 minutes and at a maximum temperature of 27°C). This stage is necessary to break down the cell walls which contain the oil droplets, as well as to fuse smaller droplets into larger droplets (that is the reason why if an olive is squeezed, no olive oil will be yielded, as oil droplets are “locked” in its cells and can be released only through special treatment). Enzymes play a major role in this process, as well as the mechanical pressure exerted by kernel pieces on the paste.
This paste is subsequently pumped and placed in the separator, where liquids (olive oil, water) are separated from solids (kernels, flesh) through centrifugation. At the next stage, olive oil is separated from water (vertical separation). The olive oil we consume is extracted in an unfiltered form at this stage. It is then up to the producer to filter the olive oil, and the ideal time to do so is right after its extraction. Filtering removes the remaining humidity and solid residues and increases the durability of the olive oil.

Virgin olive oil has to undergo physico-chemical and organoleptic analysis in order to be classified in a category.

Physico-chemical parameters which are examined and play a vital role in the quality of olive oil are: free acidity, the number of peroxides, spectrophotometric absorption in the ultraviolet spectrum (Κ232, Κ270, ΔΚ), impurities (insoluble in petroleum spirit), metal traces, alkyl esters.

Organoleptic analysis includes identifying and outlining the qualitative and quantitative odour-taste characteristics of virgin olive oil, through human senses, and classifying olive oil according to its organoleptic attributes. This method is performed by a team of selected and trained tasters and aims at classifying virgin olive oils according to the perceived intensity of the most intense negative quality traced and whether it is fruity or not.

Organoleptic analysis evaluates whether the olive oil has negative qualities and analyses its positive attributes. Some negative attributes are related with poor harvesting and storage practices before its extraction (fusty, winey, musty), some with poor conditions in the oil mill (burnt, metallic) and some with poor storage conditions (rancid, muddy).

Fruity:  It involves a set of olfactory sensations characteristic of the oil which depends on the variety and comes from sound, fresh olives, either ripe or unripe. It is perceived directly and/or through the back of the nose.

This attribute can be distinguished in unripe fruity or ripe fruity. It plays a major role in the organoleptic analysis, as if it is not identified, the tested olive oil cannot be classified as extra virgin or virgin. In other words, fruity is the aroma of the olive oil, and of its olive fruits. Apart from its intensity, an experienced taster can recognize characteristic aromas of each variety, such as fresh-cut grass, tomato or tomato leaves, artichoke, citrus fruit, apple, banana, almond, various herbs and spices, etc. Such aromas are believed to be either additional or intrinsic to the olive fruit, or derived from plants growing around the olive tree. In fact, such aromas are volatile compounds produced through the activity of the olive fruit enzymes when the olive oil is extracted (e.g. 3-hexenal for apple aroma or hexenal for green leaf aroma) and related with the following factors: variety, ripening stage, climate conditions of the particular year, water availability, fertilizing type and oil extraction practices (mainly crushing and kneading).

Bitter: Characteristic primary taste of oil obtained from green olives or olives turning colour. It is perceived in the circumvallate papillae on the ‘V’ region of the tongue. It can be pleasant or unpleasant, depending on its intensity. In any case, it is not considered a negative attribute. It results from the action of phenolic substances contained in olive oil.

Pungent: Intense biting tactile sensation, characteristic of oils produced at the start of the crop year, primarily from green olives that are still unripe. It can be perceived throughout the whole of the mouth cavity, particularly in the throat like burning, and disappears few seconds after tasting. It can sometimes cause coughing or make eyes tear. This sensation should not be confused with rancid, where burning is felt lower in the throat, is very annoying and lasts for longer (bad aftertaste). Pungent also depends on the presence of phenolic substances. Its intensity reduces when olive fruits and olive oil ripen.

The colour of olive oil is not included in its qualitative characteristics. It ranges between golden yellow tones and sapphire deep green and it largely depends on the variety, the level of ripeness of the fruit at harvesting time and on whether leaves have been milled with fruits. An olive oil might have an attractive green colour, but it might present an organoleptic defect and high acidity, thus not classified as extra virgin. Expert tasters always taste olive oil in dark-coloured glasses (blue or red) so that they are not affected by the colour of the oil.

Unfiltered olive oil is the olive oil which, after its final separation (in the oil mill), is not filtered. This means that it keeps its humidity and solid residues. Over time, unfiltered olive oil will have some sediment formed in the bottom of the bottle. The fermentation of this sediment causes amurca, an organoleptic defect. Amurca and humidity reduce the quality of the olive oil. Unfiltered olive oil might have a higher phenolic content compared to filtered olive oil (depending on the way it is filtered), yet it is more sensitive to oxidation and fermentation. Its quality is reduced faster and it is not durable, thus it must be consumed within one month after its production.

High phenolic olive oil is the olive oil with phenolic content higher than 250mg/kg and, according to regulation (EU) 432/2012, it can bear a health claim on its labelling. This claim may be used only for olive oil which contains at least 5 mg of hydroxytyrosol and its derivatives (e.g. oleuropein complex and tyrosol) per 20g of olive oil. Olive oil polyphenols help protect blood lipids from oxidative stress. A daily intake of 20g (2 tablespoons) of high phenolic olive oil is necessary to achieve this beneficial result. This type of olive oil is considered a natural food supplement, because of its high polyphenol content. It has a more bitter and pungent taste than other types of olive oil and is recommended to be consumed raw.

Rich in antioxidants, monounsaturated fatty acids and vitamin E, olive oil preserves its composition in high temperatures and cannot be easily degraded to create harmful by-products. The ideal frying temperature is 180°C, when the food is cooked without being burnt. Extra virgin olive oil is the only vegetal oil which can be used even 4 or 5 times in frying, as long as frying temperature does not exceed 220°C, food residues are removed each time and the olive oil is stored in a glass container. If you don’t have a deep fryer with a temperature regulator, you will need a thermometer to check the temperature before adding the food on the frying pan and during frying. Contrary to extra virgin olive oil, polyunsaturated fatty acids of seed oils are very sensitive to high temperatures, are degraded and create harmful free radicals and by-products already at the first frying. If you cannot afford to cook exclusively with extra virgin olive oil, which is more expensive, you can take advantage of the different types of olive oil. You can consume extra virgin olive oil raw, in salads and various dishes, and use virgin olive oil (which is the second-best olive oil after extra virgin) in cooking and frying, or use olive oil (from mixed refined olive oils and virgin olive oils) in frying.