Healthy unrefined oils, although packed with taste and aromatic, are unknown to most people. There are only a few people who realise that oils have taste and aroma. Rapeseed oil triggers the scent of blooming rapeseed fields, sunflower oil tastes like sunflower seeds, flaxseed oil is full of subtle nut flavour and coconut oil has a wonderfully delicate coconut aroma.
Unrefined oils quite often are not as clear as refined oils and have no such long shelf life. As a compensation for these ‘discomforts’, they have their own distinctive smell and taste and have a wealth of natural nutrients, vitamins, minerals, indispensable fatty acids, as well as antioxidant and other healthy ingredients.
Unrefined oils are extracted only mechanically (using expellers). High temperatures are not included in this process. Often, oils are filtered once in order to get rid of plant residues. Unrefined oils do not lose vitamin E which is a natural preservative protecting them against rancidity.
Constitute a group of oils that are extracted with the use of strong chemical substances (hexane) in high temperatures. This process is aimed at producing as much product deprived of flavour or colour as possible, which might be stored for a long time (Yes! They might ONLY be stored – they are not suitable for consumption). Anyway, decide for yourself :)
Firstly, I will familiarize you with the refining process and then we can draw a conclusion.
I. Extracting oil from seeds.
Mainly the two-stage method of extracting oil from seeds is used in the oil industry, i.e. initial pressing in a screw press and solvent extraction:
- Initial Pressing: Firstly, the material undergoes the so-called conditioning consisting in levelling the material humidity, grounding and roasting it in about 100°C. Then pressing begins. In screw presses the material is subject to pressure up to 160 Mpa (depending on the manufacturer). As the pressure is increasing, also the temperature is growing up to 160°C. Unfortunately, at the same time we say goodbye to proteins, fibber, vitamins and minerals.
- Marcs extraction: About 15-20% of fat remains in marcs. That fat is released during the extraction process with the use of hydrocarbon (petroleum derivative) solvent. Hexane is now the most commonly used solvent. Next, oil undergoes steam distillation in order to get rid of the solvent. Temperature reaches over 150°C.
II. Oil refining.
Refining comprises multistage treatment of oil with temperature, water and chemicals…
- Degumming is a process in which phosphoric acid (as well as other mineral and organic acids) and high temperature are used. Phospholipids are removed at this stage (together with lecithin which, among others, facilitates proper functioning of the nervous system), as well as protein components, chlorophyll, calcium, magnesium, iron and copper.
- Deacidification. During that process, free fatty acids are removed through adding sodium hydroxide solution (i.e. aqueous solution of sodium hydroxide); the saponification reaction takes place.
- Bleaching is a process during which oil is treated with absorbing substances, such as: bleaching earth, silica, active carbon or alumina in 90°C. Chlorophyll and pheophytins are removed. Such reactions as oxidation and isomerisation occur. As a result, trans fats, which are detrimental to health, appear.
- Deodorization (dewatering). It removes all flavours and smells thanks to steam distillation in 200-300ºC.
As a result of the refining process, oils are deprived of valuable components, e.g. chlorophyll, vitamin E, beta-carotene, iron, calcium, magnesium, copper and phosphorus. During the refining process really high temperatures, often exceeding 200ºC, are incorporated and in such temperatures unsaturated fatty acids are turned into synthetic trans acids. These acids are detrimental to health. You should decide for yourself what nutritional value such refined products might have and how close are they to the gifts of nature they were made from.