14 Dec Production & Processing
Oil is produced in mills by cold or hot compression of olives. In several cases, the filtration process is continued with filter methods Modern mills are independent industries that have plenty of water for cleaning and processing the olives. The different rooms in the mills are ventilated, dry and have thermal insulation. However, there are some small mills attached to the fields where the process is done using traditional methods. Farmers call them “liarouvia” or “oil presses”.
In the mills the processing starts with the weighing, the separation and washing of the olives. The olives which have then been placed in wooden trays are transported by elevators in a large basin which is at a higher elevation. From there they fall into cone shaped pipes which consist of crushing the millstone, and then into the mill. After the first crushing and pressing the first oil is extracted and the olive paste remains. The olive paste is then transferred to a second oil-press (with a rising pressure cylinder) which the second oil is extracted from. Finally , a third extraction is done, which is gathering the remains of the olives (kernel core) into basins. Then, the kernel goes to boilers, where it is stirred and heated up to 80-90 degrees Celsius.
At this stage, with the help of powerful hydraulic presses, more oil is extracted from the oil cakes(core) which is separated from the sediment (sludge) by automatic separation inside reservoirs and then by rapidily circulating centrifugal oil separators.
In the mills there are also reservoirs where the sediments and the water from the washing of the olives is gathered. After these remain in the reservoirs for about 20 days, they go through a centrifugal separator and give pomace oil which is suitable for the manufacturing of soap. The liquid residues (olive mill wastewater) is dried and used as fertilizer or as fuel. In the latter case it is clustered with tar cubes, at a temperature of 70 degrees Celcius. Depending on the type of machinery, the processing system, the quality and age of the harvest, this may result in different secondary products or different oil from the oil cores (pomace) from the kneaded olives or from the remnants of the flesh fruit, e.t.c. Olive oils which are on the market are distinguished into natural edible and industrial. The first are distinguished in green olives and into first, second and third grade olive oil. The average yield of 100 kilos of olives, which varies depending on the quality, the year and the treatment system is approximately 15-25 kg oil, 35-50 kg pomace and 35-50 kg olive residues.