THE REFINING PROCESS
Oils that are not classified as extra-virgin or virgin, namely lampante oils, can only be used after an industrial process, called refining or rectifying, that corrects their acidity and organoleptic defects. The refining process consists of three steps:
1. Deacidification
Oil is processed with a caustic soda solution, which binds to the free fatty acids forming soap. Then the oil is washed with water to melt the soap and achieve a neutralised or deacidified oil.
2. Bleaching
The oxidised substances of lampante oils are eliminated by combining the oil with activated charcoal or bleaching earths. At the end of this step the oil is bright yellow, a colour similar to common vegetable oils.
3. Deodorising
To remove any unpleasant odour, the oil is brought to a high vacuum temperature of 230ºC. At the end of this process, the rectified oil is virtually odourless and is left with a slight almond flavour.
EXTRACTION PROCESS BY SOLVENT
Virgin pomace, or the dried residue from the crushed olives, still contains a minimal quantity of oil; to extract it, the pomace goes to extraction plants where it undergoes a preliminary drying process.
First, the dried pomace is mixed with hexane, a solvent that facilitates the dissolution of all remaining oil and the separation of the solids from the liquid portion, called hexanol.
The hexanol is then distilled to separate the solvent and obtain the crude pomace oil, which is characterised by a naturally high acidity, unpleasant taste and the presence of all the oxidised substances that formed during the period of storage of the pomace. To become edible it must undergo a refining process to obtain refined olive pomace oil.
QUALITY AND PURITY OF OILS
With EEC Regulation 2568 of 1991, the European Community defined the quality and purity characteristics that every olive and pomace oil must have, it regulated analysis methods valid for all countries and it set the values of the parameters used to identify olive oil and its product categories.
Over the years several changes have been made, particularly Regulation 61/2011, which for the first time introduced the application of a sensory method to the assessment of oils, the Panel Test.