Taste and color of vegetable oils comes from other compounds extracted with the oil. Bleaching - removal of pigmented substances by filtering through diatomaceous earth, to which color particles adhere. Deodorization - removal of odors by being heated with steam under a vacuum. Hydrogenation - hydrogen is bubbled through the oil, usually with a catalyst such as nickel. Hydrogen binds to previous double bonds, resulting in increased saturation.
Most hydrogenated oils are solid at room temperature.
This process used in making margarines. Winterization - used to circumvent clouding of oil under low temperatures. Oil is cooled to 7 oC, and all particles that crystallize are filtered out. BHT for the prevention of oxygen binding to double-bonded carbons which cause the oil to become rancid. Add Defoamer - addition of methyl silicone for the prevention of oil from forming foam.