The olive is the fruit of the Olea europaea tree, a species cultivated for thousands of years throughout the Mediterranean region and beyond. Olives do not grow in the ground; they grow exclusively on these trees.
The Olive Tree and Its Environment
The olive tree is a slow-growing, broadleaf evergreen renowned for its longevity, with some specimens living for hundreds or even thousands of years. Young trees display smooth gray bark, which becomes distinctly gnarled and twisted with age. The leaves are small, elongated, and leathery, presenting a gray-green color above and a silvery hue underneath, which helps the tree conserve water.
The Olea europaea thrives in a Mediterranean climate, characterized by long, hot, dry summers and mild, wet winters. This species is highly drought-tolerant once established and can survive in poor, rocky soil. To produce its small, fragrant white flowers, which turn into fruit, the tree requires at least two months of winter temperatures below 50 degrees Fahrenheit.
The Olive as a Fruit (A Drupe)
The olive itself is botanically classified as a drupe, which is a type of fleshy fruit characterized by a hard, central stone or pit containing the seed, much like a peach or a cherry. The fruit starts as a small, green oval that gradually darkens as it matures, turning various shades of purple, brown, and finally black when fully ripe. The difference between green and black olives is primarily a matter of ripeness, not a different variety of fruit.
Olives cannot be eaten directly after being picked because they contain high concentrations of the phenolic compound oleuropein. This compound is responsible for the fruit’s extremely bitter taste. Oleuropein is present throughout the fruit and must be removed through processing before the olive is suitable for consumption.
Harvesting and Curing
The process of harvesting olives is determined by their intended use, whether for oil production or as table olives. Olives intended for eating must be handled with care to prevent bruising, often requiring hand-picking or gentle raking onto nets. Mechanical shakers are used for large-scale operations, especially when the fruit is destined for oil extraction, where bruising is less of a concern.
After harvest, the olives must undergo a curing process to eliminate the bitterness caused by oleuropein. Curing methods vary widely but commonly include water-curing, brine-curing, or lye-curing (sometimes called the California process). Brine curing involves soaking the olives in a saltwater solution for several months, allowing fermentation to neutralize the bitter compounds and develop the final flavor profile.