Olives and Olive Oil: How Greece Makes and Uses Both

The Dual Heritage of the Greek Grove

In Greece, the olive tree is rarely treated as a generic crop. Cultivars split strictly along functional lines: those cultivated for pressing into oil, and those nurtured for the table. The small-fruited Koroneiki dominates olive oil production across the Peloponnese, Crete, and the southern Ionian islands. Though modest in flesh, it yields an oil prized for high polyphenol levels, stability, and a distinct peppery finish. Other oil-producing cultivars such as Athinolia, Lianolia, and Tsounati provide regional nuance, yet Koroneiki remains the national benchmark.

Table olives demand entirely different fruit architecture. The celebrated Kalamata olive, grown from the Kalamon cultivar, carries a dense flesh-to-pit ratio and an elongated form with a slight curve. It is grown widely across Messenia, Laconia, and parts of central Greece. Meanwhile, northern groves produce rounded varieties such as the Conservolia, often sold as Amfissa or Volos olives, and the wrinkle-skinned Throumba from Thassos, which cures naturally on the branch through the action of the fungus Phoma oleae.

From Branch to Mill: Cold Extraction

The production of extra virgin olive oil hinges on speed and temperature. Harvesting begins in late autumn, typically between late October and January. The earliest green harvests produce agourelaio, an intensely bitter, herbaceous oil rich in antioxidants, while mid-season fruit yields rounder, fruitier profiles. Mechanical vibrating rakes and long pneumatic combs knock the fruit onto woven nets laid across the terrace floor, where workers sweep away twigs and leaves before bagging the olives in breathable crates.

At the mill, prompt processing prevents enzymatic breakdown and fermentation, which cause defects such as fustiness and high acidity. The olives are washed, destemmed, and ground into a paste using stainless steel hammer crushers. This paste undergoes malaxation, a gentle, continuous churning that allows micro-droplets of oil to coalesce. Modern standards mandate that cold extraction must keep temperatures below 27 degrees Celsius during this phase. Excessive heat increases the volume extracted but volatilises aromatic compounds and speeds up oxidation. A high-speed horizontal decanter centrifuge then separates the oil from water and solid pomace, followed by a vertical centrifuge to polish the clear oil.

Understanding Grades and Quality Standards

The International Olive Council defines the chemical and sensory thresholds that govern retail bottles. Extra virgin olive oil represents the highest standard: it must possess zero organoleptic defects, carry perceptible fruitiness, and contain a free acidity, measured as oleic acid, of no more than 0.8 grams per 100 grams. Virgin olive oil permits minor defects and an acidity level up to 2.0 grams per 100 grams. Anything exceeding these chemical parameters or showing severe sensory flaws cannot be sold directly to consumers without industrial refining.

Refined olive oil is treated with heat and chemical solvents to eliminate rancidity, neutralising its flavour, colour, and free fatty acids. When blended with a small proportion of virgin olive oil to restore minimal aroma, it is labelled simply as "olive oil" or "pure olive oil". Olive pomace oil represents the bottom tier, chemically extracted from the residual solid cake left after the initial pressing. For the home cook, extra virgin remains the sole grade suitable for dressings, raw finishing, and traditional Greek ladera stews, where the fat serves as a foundational seasoning rather than merely a cooking medium.

Curing the Raw Table Olive

Direct from the tree, fresh olives are completely inedible due to high concentrations of oleuropein, a bitter phenolic compound. Transforming them into a succulent table fruit requires patient debittering and curing, traditionally achieved through brine, salt, or water baths without industrial lye solutions.

Kalamata olives are picked ripe and purple-black. Producers slit the skins or leave them whole, submerging them in a sea-salt brine often finished with red wine vinegar and a topping of olive oil to seal the container from airborne spoilage. The brine leaches out the oleuropein over several months through natural lactic fermentation, developing a firm bite and a tart, vinous acidity. Green olives, picked unripe in early autumn, are often gently cracked with wooden mallets to speed up the process, submerged in repeated changes of clean water for several weeks, and then preserved in lemon-scented brine with wild fennel or oregano.

Buying and Storing in the Kitchen

Quality olive oil deteriorates quickly when exposed to light, heat, and oxygen. When purchasing, choose dark glass bottles, tinplate cans, or ceramic containers. Clear glass bottles on brightly lit supermarket shelves accelerate photo-oxidation, turning fresh oil flat and rancid within weeks. Check the harvest date on the label rather than solely the expiry date; oil is at its peak within eighteen months of pressing.

Store the container in a cool cupboard away from the stove. Storing oil inside the refrigerator is unnecessary and can cause waxy fractions to solidify, while standing it next to an oven degrades delicate aromatic esters. Buy container sizes suited to your consumption: once opened, aim to consume a bottle within eight to ten weeks. For cured olives, keep them fully submerged in their brine in the refrigerator, topping with a thin film of olive oil if exposed to air to prevent mould formation.