Olives to Oil

The lion’s share of the world’s olive crop is used for oil—only a handful are processed for eating.

The first Middle Eastern oil boom wasn’t based on petroleum. It was fueled by olives. Neolithic people were plucking the bitter fruit of the wild oleaster tree some 10,000 years ago, and by 3000 BC, the tree was cultivated, probably in Palestine or Syria.

In antiquity, olives provided jobs, drove trade and anointed kings. Burning olive oil in clay lamps was the only source of light. Status was displayed by being rubbed head to toe with oil. The fruit’s preeminence is encoded in art and mythology; the oldest surviving Latin prose text, Cato’s On Farming (circa 175 B.C.), devotes more space to olive growing and oil-making than any other topic.

Botanically, the olive tree is an evergreen with distinctive silver-green foliage. It’s generally accepted that the trunk of an olive tree can live for 700 years, but since its roots are constantly sprouting new shoots, the “age” of the tree is obscured by its ability to reproduce itself. Tour guides in Jerusalem’s Garden of Gethsemane claim the trees are 5,000 years old, and in a sense, that’s likely true.

The lion’s share of the world’s olive crop is used for oil. Only a handful are processed for eating. Under-ripe olives are green. As olives mature, the color changes to deeper green, purple or black. If you plucked an olive off a tree and ate it, you’d be stunned by its bitterness. Olives are tamed by curing. Methods vary according to ripeness and local tastes; techniques include curing in water, brine, salt, oil, or an alkaline solution, or a series of such treatments.

—By Jo Marshall, a food writer in Deephaven, Minn.