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Prior to 1900, vegetable oil was processed out of its natural state (such as corn oil from corn) by small, slow, cold- temperature batch presses. But in the 1920s, industrialists realized that human-dependent small, batch cold-pressing was too slow and not profitable enough, so they switched to automated heat and chemical processes that produced high volumes of oil at a greater profit.<\/p>\n\n\n\n
Unfortunately, these new processes did very bad things to oils. In simple terms, fatty acids are chains of carbon atoms with hydrogen atoms filling the available bonds. A fatty acid is considered \u201csaturated\u201d when all available carbon bonds are occupied by a hydrogen atom. Monounsaturated fatty acids lack two hydrogen atoms and polyunsaturated fatty acids lack still more. The level of hydrogen atom \u201csaturation\u201d determines how stable, or resistant to rancidity, a fatty acid is, when exposed to heat, light, and oxygen. Saturated fatty acids are the least likely to oxidize\/go rancid (create free radicals), monounsaturated fatty acids are the second most stable, and polyunsaturated fatty acids are the most fragile under these conditions.<\/p>\n\n\n\n
The heat and chemical processing of polyunsaturated oils goes like this: Seeds, kernels, fruits, and nuts are hulled and ground, which exposes their oils to air and light and begins the rancidity process, of creating free radical oxidation.<\/p>\n\n\n\n
After hulling, the pulp is cooked for up to 2 hours at high temperatures \u2013 creating more free radical oxidation. Subsequent pressing also exposes the oil to heat, causing a chemical reaction that essentially creates the same chemical constituent as plastic, varnish, and shellac. Another method of removing the oil from raw sources uses chemical solvents, which also infuses the oil with free radicals.<\/p>\n\n\n\n
After the initial heat and chemical processing of vegetable oils, the oils are then often \u201cde-gummed\u201d: Phosphoric acid (used in bathroom cleaners) and high temperatures are used to remove impurities and nutrients, a process that increases rancidity\/free radical oxidation. To remove free fatty acids and minerals from the oil, sodium hydroxide [i.e., lye, which is also used in Drano and Easy Off oven cleaner] and high temperatures are used. Subsequent bleaching removes undesirable pigments from oils. At this point, the oils may possess pungent odours and tastes that must be removed through a high-temperature deodorizing process.<\/p>\n\n\n\n
Some of these oils end up in row open row of glistening sanitary – looking cooking oils on your supermarket shelves. But much of this heat and chemical- processed oil is partially hydrogenated. This process alters the molecular structure of the fatty acid by adding hydrogen atoms, changing the chemical structure from a \u201ccis\u201d shape that is recognised and utilized by human cells to a \u201ctrans\u201d shape that is foreign and lethal to human physiology. Partial hydrogenation turns polyunsaturated vegetable oil into a hardened – butter – like product that holds up better than liquid oils in food-production processes and has a longer shelf life.<\/p>\n\n\n\n