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Biochemical Engineering for Biomass Refinery

How olive oil is processed

The olive tree is native to the Mediterranean basin. Archeological evidence shows that olive oil was produced as early as 4000 BC. Besides food, olive oil was used historically for medicine, lamp fuel, soap, and skin care.

 
The majority of olive oil is produced in the European Union, with Spain being the largest producer of olive oil in the world, followed by Italy and Greece. In the United States, olive oil is produced in California, Arizona, Texas, Georgia, Florida, Oregon, and Hawaii.
 
Variety and maturation are two of the most important factors of olives that influence the quality and taste of the final olive oil. There are hundreds of varieties of olive trees. A wide range of olive varieties are used in the production of olive oil. These include Mission, Manzanillo, Sevillano, Arbequina, Koroneiki, Arbosana, Ascolano, Frantoio, Leccino, Pendolino, Maurino, and Coratina.
 
Olive oil production begins with harvesting the olives. Traditionally, olives were hand-picked. Currently, harvesting is performed by a variety of types of shakers that transmit vibrations to the tree branches, causing the olives to drop into nets that have previously been placed under the tree canopy. Increasing ripeness generally increases yield in terms of release of olives from the tree branches. However, over-mature olives do not possess the best sensory qualities for oil production. Therefore, harvesting time is frequently a compromise between harvesting efficiency and final oil quality.
 
After harvesting, the olives are washed to remove dirt, leaves, and twigs. After the twigs are filtered out with grids, the fruit is ready for processing into oil. Fewer than 24 hours from harvest to processing produces the highest-grade oils.
 
Traditional Olive Oil Processing
 
Traditional olive oil processing begins with crushing the olives into a paste. The purpose of the crushing is to facilitate the release of the oil from the vacuoles. Large granite stones such as the one shown in the photograph on this page were traditionally used to crush olives. In the early days, donkeys were used to pull the stone wheel around. This particular mill is motorized and also includes wiper blades, both of which are more recent additions to the traditional stone mill.
 
The next step in the process involves malaxing the paste (mixing the paste). The paste is mixed for 20–45 minutes to allow small oil droplets to combine into bigger ones. This process ensures the olives are well ground and allows the fruit enzymes to produce desirable aromas and flavors. Longer mixing times increase yield; however, they may also result in increased oxidation and decreased shelf life and quality.
 
How olive oil is processed
 

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Provided by Institute of Food Technologists