water added during these two steps. High temperatures are used to increase the yield of olive oil obtained from the paste. Alternative configurations Some producers, in order to maximise product quality, choose to combine the traditional grinding method, the stone mill, with a modern decanter. This technique produces more selective grinding of the olives, reduces the malaxation time olive paste, and avoids the complicated cleaning of the olive press fibre disks. Because the use of the stone mill requires a loading and unloading phase, this extraction method is discontinuous, i.e., there are times when all the machinery is stopped, therefore it is generally not used on a large commercial scale, being applied only by small scale olive mills producing high quality olive oil. Consumer point of view High quality olive oil can be obtained by all the methods if proper measures are taken. Olive oil quality is equally dependent on the quality of the olives themselves and on the time they have to wait from harvesting to extraction, in addition to the extraction method itself. The two main agents that cause the degradation of olive oil are oxygen and light. Once an olive is harvested, it should be pressed within 24 hours. Oxidation begins immediately upon harvesting. In the period between harvest and grinding, the fruits' enzymes are very active and increasingly degrade the endogenous oil, and therefore oil obtained after a longer wait is of lower quality, presenting higher acidity (free fatty acids percentage). In addition, if additional oxygen is allowed to interact with the olive paste during the extraction process, the acidity level will increase further. Sealed extraction methods are best to prevent the continued introduction of oxygen, as well as light to the oil. After extraction is complete, in most cases unfiltered olive oil appears somewhat cloudy, mainly due to the presence of minute amounts of water and suspended solids of olive pulp and seed. This type of oil is therefore sometimes called cloudy or veiled olive oil. It is common practice that unfiltered olive oils are then "racked" for a time, i.e. stored in cool stainless steel silos with a conical bottom that are pumped free of oxygen to enable the precipitation and separation of the two phases and facilitate later filtration; it will also contribute in the integrity and stability of the oil. Future prospects The future of olive extraction points to reducing the negative