Olive oil is an oil extracted from olives, the fruit of the olive tree. It is typically imported and sold in stores, but making olive oil at home is possible. With a little effort and fresh olives, you may find that making olive oil at home results in a delicious treat.
The first step in making olive oil is selecting the right olives. Either green or black olives can be used, but they must be fresh and untreated. Olives may also be obtained directly from a tree by picking or shaking. If there are no olive trees where you live, fresh olives can be purchased from an olive producer, at a farmer's market, or in a specialty supermarket.
Olives should be separated from leaves, twigs, and other debris and cleaned completely before use. When making olive oil, it is not necessary to remove the pits. Removing pits will actually detract from your final yield.
The olives will then be crushed with enough force to make a paste. A traditional method of crushing is a mortar and pestle, although anything that is able to grind the olives into a wet paste will work. One helpful tip is to crush the olives as slowly as possible. It may seem tempting to use a food processor, but if the olives are made into a paste too quickly, bitter flavors may be present in the oil.
After crushing, the olive paste should be slowly mixed for 20 to 40 minutes. This process is necessary and critical for successful olive oil. A slow mixing process is necessary because it allows time for microscopic droplets of oil to combine into larger ones, which will then be extracted. If this step is left out, your oil yield will be much smaller.
The paste should then be spread and pressed to squeeze out the vegetal liquid, a mixture of both oil and water. Letting the liquid sit is the traditional method for separating the oil and water. After a long enough time has passed, the oil and water will naturally separate. If you have the patience, this can be a good at-home method.
If a centrifuge is available while making olive oil, the separation process will be both faster and more thorough. Centrifugal separation works by spinning the vegetal solution fast enough so that the difference in density between the oil and water causes the liquids to separate and gather or collect in different areas. Once the oil has been separated from the water, it should be filtered again to remove any particles left behind. This step can be skipped to produce a cloudier, more natural appearance.