Olive oil is widely used in many households purely for its health benefits. In terms of cost, olive oil is still not affordable by everyone. Converting olive fruits into olive oil is a complex process. Olives are staple food in the Mediterranean regions.
Soft olives are plucked from the olive trees using special tree-shaking device in such a way olives don’t fall down but on a net. Those fallen from the trees might get bruised affecting the quality of olives. That is why we see different quality grades of oil depending on how olives were picked. Oils made from unripe olives are light to deep green color while those from ripe ones are golden color. Oil from ripe ones are said to contain more healthy nutrients. To produce about one liter of oil around 4.5 kilograms of olives are required.
There are lots of varieties of olives, some of which contains health promoting polyphenols while others don’t. After the olives are plucked with very minimum or no damage at all to the fruits, they are taken to the mills. Here they are crushed in stainless steel rollers and ground into a paste. In order to separate the oil from the paste, a process called malaxation is done.
Malaxation could be done with or without using water. Normally water is slowly added to paste and stirred for about 20 to 40 minutes in closed mixing chambers. The mixture is heated to a temperature of 27 degree centigrade. The oil slowly starts to cling to similar oil molecules and becomes easy to separate.
The mixing time and temperature is proportional to the oil yield. But it could not very high because oil starts to oxidize at such temperatures when stirred for a long time. Hence 27 degree centigrade would be an ideal one. This would significantly reduce the shelf life of the resulting oil. A study says that malaxation without water was found to yield better quality oil compared to the one with water. Addition of water during malaxation is found to reduce the content of phenols.
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Now the paste is sent via a centrifuge. Centrifuge is a compartment which is rotated at a very high speed on its central axis in order to separate oil from the paste. When rotated at high speeds, paste rushes to the sides of the compartment while oil and water remain in the centre. Oil is then separated from water. Before bottling the oil, it is stored in stainless steel containers at about 65 degrees Fahrenheit.
The remains after the extraction of oil are called pomace. The pomace may contain residual oil. This oil is again extracted by using steam, hexane or any other solvents. This is low quality oil called pomace oil.
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