Fruit of the olive tree, which has an exceptionally long lifespan, the olive is one of the oldest cultivated fruits. Although it is not known for certain when the wild olive tree was first cultivated, information gathered from archaeological sites has led some historians to believe that it might have been somewhere between 5000 and 3000 B.C. in Crete, from which cultivation then spread to Egypt, Greece, Palestine, and Asia Minor. The history of the olive tree is also the history of agriculture and of the Mediterranean basin.
The olive branch is present in the story of the Flood, and oil mills existed as early as 3000 B.C. A symbol of peace and wisdom, the olive tree plays an important role in mythology, where it was venerated by the Egyptians, the Greeks, and the Romans. The olive tree was introduced into America during the Renaissance by the Spanish and Portuguese. Entire populations were able to live on olives and olive oil, which also provided lamp fuel and medicinal remedies. Today the cultivation of olives still constitutes an essential part of the economy of many Mediterranean countries. Italy and Spain account for approximately 50% of the global production of olives and olive oil. Greece, Turkey, Syria, Morocco, Tunisia, Portugal, and the United States are the main producers of table olives.
The olive tree usually grows between 10 and 23 feet in height, but it can sometimes grow as high as 50 feet. It produces an abundance of fleshy fruits differing in size, flesh, and colour according to the climate, the method of cultivation, and the variety of the tree. The flesh contains a ligneous pit. Olives reach their maximum weight 6 to 8 months after the tree has bloomed.
Olives directly off the branch are inedible, as they contain an extremely bitter glycoside that irritates the digestive tract. To make them suitable for consumption, they must first be macerated and then undergo various processes, which differ according to the variety of olive and the region of cultivation. Table olives must be medium- or large-sized, the ideal weight being between 1/8 and 1/4 ounce. They must also be easy to pit, and their skin should be fine-grained and elastic, so that it is able to resist shocks and brine. For optimal preservation, they must contain a minimum of 4% carbohydrate and very little oil. Green olives, are harvested when they reach their normal size and just before they change colour. They are processed according to two methods: The Spanish method, which uses fermentation, and the American method, which does not. The Greek method, which involved soaking the olives in brine, is only used for ripe olives (black). The aim of all of these methods is to make olives suitable for consumption by reducing their bitterness.
The Spanish method, which produces green fermented olives, involves soaking the still firm and unripe fruits (which are a light green at this point) in a caustic soda solution to reduce their natural bitterness; they are then washed and soaked in brine, which promotes fermentation and changes the colour of the olives to their characteristic "olive green." The original brine is changed before marketing and the olives are packed in smaller containers. They are often sold pitted and stuffed. The American method (canned ripe olives) differs from the Spanish method in that the olives are soaked in brine without fermentation. The olives are picked when half-ripe, just as their colour starts to turn form yellow to red. They are then soaked in an alkaline solution and exposed to air, which causes them to turn black. These black olives are then packed in brine, canned and sterilised. This method is widely used in California.
The Greek method uses fully ripe dark purple or black olives. Because the use of caustic soda solutions is not authorised in Greece, the olives are prepared according to a gradual process of fermentation in brine, lasting 6 months. Other methods can also be used which may or may not call for brine in addition to caustic soda. Another method involves preserving the olives in salt; this method causes their skin to wrinkle but leaves the olives otherwise intact. Olives prepared in this way have a fruity and slightly bitter taste. Once ready for consumption, the olives are either left in their barrels or packed in containers to be sent to market. They are often pitted and stuffed with sweet pepper, onion, almonds or anchovies, or spiced. Olives may also be sold halved, quartered, sliced, chopped, or pureed.