Friday, June 24, 2011

Oil Processing

     Around the web and even in nutrition text books, we often  are referred to the vague term processing in regards to food stuffs manufacturing. I think most health conscious individuals acknowledge that processing is generally deleterious to the health providing qualities of food. For example refined flour, refined sugar, refined oil, etc. However I have often found that understanding the so called processing that takes place, even if only in a rudimentary manner, gives me further motivation to not eat industrialized food stuffs. I guess one might say actually knowing the methods behind the madness makes the food that much more unappeasing. Today I wanted to go over the steps from which a soybean, cotton kernel, corn kernel, and other seeds become industrial oils. I attribute much of the following information to be sourced from the online Encyclopedia Brittanica and Fats that Heal, Fats that Kill* by Udo Erasmus.

      The initiation of the process that takes a commodity seed to oil begins with general cleaning of the seed and possibly cooking. On one hand, the cooking is neccessary. Many of the seeds used, such as soy beans contain anti-nutrients such as trypsin inhibitors (1) that are only inactivated with heat. The raw oil would otherwise be inedible. Another advantage of this specific step is that heating the seed makes the pressing process (this is the following step) or the chemical extraction process (to be explained later) easier by denaturing the cell membranes which encompass the desired oils. However on the other other hand, the cooking process greatly accelerates the onset of rancidity exposing the oils to both air and heat, and possibly light (Textbook of Medical Biochemistry, Ramakrishnan, P.41) . This is confounded by the fact that most of the common commercial oils contain high proportions of the more delicate polyunsaturated fats( Ramakrishnan, P. 267).
Typical oil seeds; corn, cotton, soy, sunflower

     The next step in the process is the mechanical pressing of the seeds to extract oil. We often see this on the label of more traditional oils such as coconut, palm, and olive oils as expeller pressed. The method essentially involves subjecting the raw material to high amounts of mechanical pressure. Often times what is called a screw press is used (illustration below). This involves a continuoulsy rotating screw shaped auger pushing the seeds forward against a metal press. The friction created by the rotating auger combines with the high heat to squeeze the oil out of the seeds.The oil is released by of hole or slits in the press while the remaining solid mass(seed mash) is left behind for further processing. Accoridng to Erasmus, (p. 95) it is said that the pressing temperature takes place at 85 to 95 degrees Celsius or185 to 203 F, which subsequently  greatly increases the rate of lipid rancidity. When the end product of this mechanical extraction is sold without further processing, we have the true unrefined oils.
screw press, sounds like a resistance training exercise.

     Another consideration here is that saturated fats such as coconout and palm are less prone to be damaged by the high temperatures used (Ramakrishnan, P. 39,41). Although some companies claim to use cold pressed, Erasmus states there is not a set industry standard for this criterion or claim. The next procees described is solvent extraction, a more modern industrial practice used to further enhance the oil extraction from the seed mash, or that can be used independent of mechanical pressing.

      Solvent extraction is a very efficient means of oil extraction used by large scale industrial operations. Solvents such as heptane or hexane are used to dissolve ground seed meal or the remaining seed mash described above whilst also using mechanical agitation (think stirring on steroids). The solvent-oil mixture is separated from the naturally occuring protein and carbohydrate portion of the original seed. The same thing is going on here as the saying about oil & water dont mix. The heptane is similar to oil so it mixes while the protein, carbs, and water are repelled.) The solvent can then be evaporated at roughly 150 degrees Celsius or 302 F. The seed oil is then left behind with very minute quantities of the solvents left behind. The ranges I have found are in the range of  10-21 ppm (2). Although I am not a fan of hexane, I will say that the concentration left behind in oils does not seem to be a major casuse for concern (although there are many). What may be disconcerning to some health conscious consumers is that the solvent extracted oil may still be labeled as unrefined at this point, again placing greater importance to choosing  the expeller pressed brands if hexane is a key concern for the consumer.For the more commonly sold vbegetable oils and the oils labeled as refined, such as Spectrum refined coconut oil or NOW brands natural coconut oil, further chemical processing takes place.

       Degumming, or alkali refining is a process that removes the phospholipids naturally occuring in seed oils, such as soy lecithin (phospholipid wiki). Left behind proteins and polysaccharides (complex carbohydrates) from the preceeding extraction methods are also removed during degumming. As far as the possible health worries Erasmus claims that degumming removes chlorophyll, calcium, magnesium, iron, and copper. The degumming process is generally carried out at roughly 140 F (Erasmus, P. 96).

      During the process known as water refining or just refining, oils are mixed with strong bases  (proton or hydrogen ion acceptors that completely dissolve in water) such as sodium hydroxide (NaOH). Refining is meant to further remove free fatty acids from oils.The free fatty acids form soaps with the bases (eg NaOH) and dissolve in the hydrophilic (water loving) portion of the mixture. This aqueous solution is then drained off, or centrifuged and then drained off from the oil. The temperature at which refining takes place is roughly 75 degrees celcius or 167 F. Phospholipids, polypeptides, and minerals are also lost in this process (Erasmus, P. 96). Before moving on, I have to make note that at this point, the proccessing of the oil has not only removed health promoting components of the oil like lecithin and minerals like iron, zinc, and so forth, but that they are then sold back to consumers in the form of soap, soy lecithin, etc.Its pretty crazy. Although pigments may still remain., theyl'l be gone soon enough. Next up are bleaching and deodorizing.

     Bleaching is used if removal of the pigments is desired. The remaining oil treated with various bleaching agents, which may include fuller’s earth (a natural earthy material that will decolorize oils), activated carbon, or activated clays. The bleaching agents mentioned remove beneficial pigments such as chlorophyll and beta-carotene.Magnesium is stored in the chlorophyll and beta carotene is a pre cursor to Vitamin A. Additionally if the centrifuge method was not used during refinement, additonal FFAs may be removed during bleaching. The temperature at which this process takes place is 110 Celsius or 230 F. According to Erasmus, this process forms toxic peroxides as well (Erasmus P. 96).

    Deodorizing involves steam distillation under pressure. The deodorization removes any aromatic compounds that impart any remaining pungent taste or odor to the oil.  Erasmus notes that deodorization takes place a highly destructive temperatures in the range of 240 to 270 degrees Celsius or 465-520 F! And this process is said to last 30 to 60 minute depending on the oil. These temperatures are high enough to result in carcinogenic mutations to the remaining fats in the oil (3).  Trans-fatty acids are also formed at such high temperatures. Although deodorization removes some of the peroxides formed during earlier stages of processing , as well as pesticide residues, tocopherols (Vitamin E) and plant sterols are also removed as well. (Erasmus P.97)

      At this point, the oil processor has yielded a valuable commodity. Flavorless, colorless, tasteless oil (yum!) that can be further handled to add flavors, textures, colors, etc. that meet the consumer's demands for highly palatable cheap frankenfood. However, with the exception  of some of the healthier oils, such as palm, coconut, and olive oil, most of these will have synthetic antioxidants added in back as well, such as butylated hydroxytoluene (BHT), or tertiary butyhydroquinone (TBHQ). These replace the plant's natural antioxidants such as the above mentioned phytochemical, Vitamin E, and beta carotene.

     As you can establish for yourselves at this point, the processing of oils, while an intriguing science, does not appear to be the optimal method of foos extraction for promoting good health. In fact up until the late 20th century there were wide spread nutrient deficiencies due to processing food without the realization that key nutrients were lost. It was believed that  biologically complete diets need only to consistr sufficient proteins, carbohydrates, fats, inorganic salts, and water (4). Unfortunately or fortunately it was later discovered that we needed micronutrients in the form of vitamins, minerals, and phytochemicals. While fortification of foods with certain nutrients has probably helped, I still don't believe it's enough. Below I have created a table based the calculations of Weton A. Price in Nutrition and Physical Degeneration (P.246 & 247) to show just how lacking the American diet was compared to traditional diets in his time.The numbers are how many times more of the listed nutrient (eg Ca) that the traditional cultures recieved in contrast to urbanized  Americans at the time (mid 1930's) through diet. Its pretty amazing.

    With that said, processed oils (along with processed sugar and flour) just make up too much of the American diet. The USDA recently reported that we are consuming 1.4 billion pounds of cottonseed oil, alone, annually (see here).We are eating the oils of these seeds in proportions that we would never eat in the form of real food. I have blogged on this previously as well (here). The nutrient density is just not there in addition to the synergistic effect that I believe real food nutrients provide when eaten together as one in the context of real food.

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* While I found Erasmus's book helpful for this post, I think it is important to disclose he does sell his own oil blends that are focused more on the EFA rather than the coconut oil, palm, and olive oil I would reccomend. I believe eating the fat from sources like coconuts and olives that are mostly fat, when found in nature, is probably more suitable for humans in that eating large amounts of fat from these foods is not new to us as a species.

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