Raw olives are olives that have been harvested from the tree but not yet cured. Olives are typically grown in areas with Mediterranean-like climates, including Greece, Italy, California, Jordan, Israel, South Africa and others, and they are native to the eastern Mediterranean region. Any of the varieties of olives cultivated around the world can be raw.
The curing process renders the olive edible; raw olives are incredibly bitter and not fit for consumption due to a naturally-present chemical called oleuropein. The brining process removes the chemical while preserving the olives and adding flavor. The fruit is typically harvested in the late fall or winter and then processed for preservation.
People have been preserving olives for thousands of years; there are references to olives in many ancient texts, including the Bible and Homer's Odyssey. The fermentation process used can be done in a factory or at home in small batches. Olives can be processed at almost any stage of their development, from green to fully ripe. The best are selected for their firmness before processing and then washed.
The raw olives are slit and then added to a solution that helps remove the bitter compounds from the fruit. This solution varies from method to method but can include lye, salt or vinegar. The olives are soaked and cured for anywhere from two weeks to three months. Other preservation methods include salt curing and water curing; all methods result in fermentation.
The brining process ferments the fruit and leaches out the bitter oleuropein and other chemicals called phenols. It also brings about the production of lactic acid, which aids in the fermentation process because it is a naturally-occurring preservative. After the olives are brined, they can be flavored with garlic, marinades, vinegar or oils. They also can be stuffed with pimentos, cheese or anchovies, among other ingredients.
Olive oil uses raw olives, but more care is given to determining the right time to harvest the fruit. Ones used for olive oil must be harvested when the olives are perfectly ripe in order to create an oil that is neither too bitter nor rancid. The olives are selected and then crushed to produce virgin oil. For lower grade oils, they are pressed a second time.
A number of countries consume olives as a staple food, but their widespread popularity has led to the fruit being one of the most cultivated foods in the world. Cured olives and olive oil contain a number of heart-healthy compounds, including monounsaturated fats. Studies have shown that olives also have antioxidant properties.