ABSTRACT
Introduction Like most vegetable oils, non-edible forms of olive oil are neutralized, bleached, and deodorized to obtain a bland fatty material which is usually blended with natural oil. e industrial process of refining should be considered as a means to restore a defective but still valuable product. Lampante oils usually have market prices higher than those of seed oils. Factors such as acidity, peroxide value, and flavor score determine whether an oil is suitable for consumption or has to be refined. Each processing step has specific functions for removing certain major or minor constituents. Alkali refining removes free fatty acid, phospholipids, and pigments. In the presence of water, mucilage and resinous substances become insoluble and separable. us, the two treatments, neutralization and removal of mucilaginous substances, can take place at the same time. e elimination of mucilage is important because such substances reduce the capacity of activated earths and carbon used for bleaching. Bleaching reduces chlorophylls, carotenoids, and residual fatty acid salts. Deodorization removes volatiles, oxidation products, carotenoids, free fatty acids, pesticide residues and part of sterols, tocopherols, and hydrocarbons. Refining also destroys peroxides and thus the stability of the oil is increased. If the oil is winterized, waxes are removed. is additional step is necessary for olive oil-residue oil. An ideal refining process aims to keep unchanged the structure of triacylglycerols and minimize configuration changes of fatty acids as well as losses of valuable constituents such as tocopherols. However, such losses are inevitable; therefore, the addition of alpha-tocopherol at a maximum level of 200 mg/kg to refined olive oil and olive-pomace oil is permitted by the International Olive Oil Council (COI,2003) and the Codex Alimentarius to restore natural tocopherols lost in the refining process. e first step of refining is neutralization of free fatty acids. Low acidity oils are easily treated by sodium hydroxide solution. Neutralization of high acidity oils, especially husk oil, is more difficult. Oils neutralized by alkali are subjected to bleaching
by earths and, if necessary, by activated carbon. Synthetic silicas can be used in combination with bleaching earths. If free acids are removed by physical refining, the oil needs a prerefining process. It is first degummed and bleached and then deacidified by deodorization. Free fatty acids do not disturb the activity of decolorizing earths. Physical refining takes place in a stainless steel deodorizer where there is a vacuum of 0.1 mm of residual pressure, the temperature is approximately 230°C and there is a flow of direct steam. When the process is over, the oil has practically zero acidity and peroxide value.
