Vegetable Oil Refining Vegetable Oils Refining is necessary for vegetable oils & fats or animal oils & fats so they can be used for cooking and frying foods. Chemically speaking, oils are Tri-Glycerides or “Fatty-Acid Glycerin Esters” (FAGE). One Glycerin molecule combines with three Fatty-Acid molecules to form one FAGE. Oils are a blend of different types of FAGEs. The Oils can be differentiated on the basis of the length of carbon chain in the Fatty Acids and the number and location of double bonds in the carbon chains of the Fatty Acids. Greater the number of double bonds between two carbon atoms, the greater is the extent of “unsaturated” fatty-acids in the fatty-acid profile of the oils. “Unsaturated” oils and fats are considered more desirable than “saturated” oils and fats from health point of view.
What is RBD Oil?
Refined Vegetable Oil is commonly called Refined, Bleached, and Deodorized (RBD) oil. As described earlier, these are the three main steps in the refining process; although additional steps are required in most cases.
Chemical Refining In Chemical Refining, Vegetable Oil is treated with caustic lye for separation of free fatty acids from oil. This is a conventional process that can be applied to all oils. A byproduct of alkali refining is soap-stock, which is used for manufacture of low quality washing soap. Alternately, the soap-stock can be treated with acid to recover fatty acids. The waste-water from refinery requires extensive treatment. This can be avoided by alternate Physical Refining process.
Physical Refining In Physical Refining, Vegetable Oil is subject to distillation to remove free fatty acids. The alkali treatment is completely avoided. This reduces the amount of waste water and eliminates production of soap. This process is becoming more popular.
Degumming The purpose of Degumming Vegetable Oils is to remove Gums. All oils have hydratable and non-hydratable gums.
a. Water Degumming: Hydratable gums are removed by treating oils with water and separating the gums. The gums can be dried to produce lecithin.
b. Acid Degumming: Non-Hydratable gums are removed by treating oils with acids and separating the gums.
Neutralizing The purpose of Neutralizing Vegetable Oils is to remove Free-Fatty Acids (FFAs). Traditionally, FFAs are treated with caustic soda (NaOH). The reaction produces Soaps which are separated from the oil. Because trace amounts of soaps remain in the oil, the oil is either washed with water or treated with Silica. Some processors prefer not to perform caustic neutralizing. Instead, they prefer Physical Refining in which the FFAs are evaporated from the oil under high temperature and 5-10T/D Sunflower/Peanut/Cottonseed/Soybean oil refinery machine. This process can be combined with deodorization step described under FFA stripping. Physical Refining process is preferred because (a) it does not produce soaps; (b) it recovers fatty acids that provide better cost recovery; (c) there is smaller yield loss compared to caustic refining—especially for oils with higher FFAs; and (d) it is a chemical-free process. Bleaching The purpose of Bleaching is to remove color pigments contained in Vegetable Oils. The oil is treated with Bleaching Clays that adsorb the color pigments. The clay is filtered and the clean bleached oil is stored for further processing. Process flow diagram is attached. Deodorizing The purpose of Deodorizing Vegetable Oils is to remove odor substances. The oil is subjected to steam distillation under high temperature and 5-10T/D Sunflower/Peanut/Cottonseed/Soybean oil refinery machine to evaporate all odor substances. The resulting deodorized oil is almost bland and tasteless.