Soybean oil
An oil press can be used to process soybeans into high-quality soybean oil!
Essentially, there are two ways of processing soybeans. Depending upon the method, the soybeans can be processed either shelled or unshelled.
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1st processing method with the screw press
The first method is a purely mechanical pressing of the soybean. The soybean is pre-treated accordingly (urease degradation – see Florapower Thermo-Major). The subsequent pressing is carried out using a screw press. This method produces high-quality soybean oil and soybean press cake. The press cake can be used directly as animal feed or as a raw material for an animal feed plant. Trub oil is filtered in batches (coarse filtration, fine filtration, safety filtration) to produce pure oil.
2nd processing method using solvent extraction
The second processing method consists of solvent extraction of the oil using hexane, which yields multiple products. The third method produces full-fat soy flours, which differ in their enzyme activity.
Soybean oil and soybean meal or soybean press cake are therefore obtained by means of solvent extraction or by mechanical pressing of the soybeans. Although extraction reduces or completely destroys important ingredients (e.g. minerals) in the beans, its advantage lies in the greater oil yield. The advantage of processing soybeans with screw presses, however, is that even small capacities of soybeans can be processed.
The soybean oil obtained from both solvent extraction and pressing can then be refined in various process steps. Refining has a strong influence on the composition of the oil, as it splits off the free fatty acids and phosphatides in particular and greatly reduces the proportion of plant sterols, tocopherols and trace elements contained in the oil.
1st processing step – degumming
The first processing step is “degumming”, i.e. the separation of phospholipids in order to make the crude oil suitable for transportation and storage. For this purpose, the crude oil is mixed with around 2 to 5% water and acid (usually phosphoric acid), which causes the phosphatides to adhere to the boundary layer between the water and oil, allowing them to be separated by means of centrifugal separation. The phosphatides are then dried under vacuum and bleached. The resulting product has a viscosity similar to honey and is made up of around 50% oil and 50% phospholipids. The phospholipid fraction is then freed from the oil by means of a whole series of solvent extractions. This produces oil-free phospholipids as solids, which are also known as soy lecithins.
2nd processing step – refining
The second step is the refining of the degummed soybean oil. There are two different ways of doing this, which differ in the way the free fatty acids are removed, either by “acidic” or “alkaline” saponification. As a rule, however, soybean oil undergoes alkaline saponification. This involves hydrolytic cleavage of the oil into glycerol and higher fatty acids, which then precipitate as alkali salts (the “soaps”). This type of saponification also separates the last remnants of the phospholipids. Partial pigment destruction or adsorption on the heavy phase usually results in a certain bleaching effect during this stage of processing. After the resulting soap solution (“soap stock”; can be used in soap production) has been separated from the neutralized oil by means of subsequent centrifugation, the oil is “washed” to remove all traces of soap from the oil and bleached to remove pigments and cholorphylls.
Final processing step – deodorization
The final processing step is the deodorization of the crude oil. Here, undesirable odors are eliminated using water distillation (“stipping”) under a high vacuum at temperatures of around 250° C. Finally, the refined oil is cooled and citric acid is added to prevent an oxidative rearrangement reaction.
The oil extraction described above produces soybean meal. Together with the hulls, this makes up around 80% of the soybean mass and has a very high protein content of around 44% (the protein content resulting from the extraction of hulled soybeans is even higher), which is why it is often used in the manufacture of soy products or as animal feed. The heat sensitivity of the urease enzyme and the protein inhibitor is therefore exploited in the industrial production of soy products and animal feed by subjecting the products to a heat treatment (known as “toasting”) to inactivate the antinutritive substances. This also greatly reduces or completely removes the urease content. The soybean cake, which is produced during soybean oil extraction, is also treated using heating processes before it is further processed into protein-rich animal feed in order to inactivate the harmful antinutritive ingredients (especially trysin inhibitors, lectins, phytates). However, the heat should not be too high, as otherwise it reduces the protein content of the soybeans too much.
Soy concentrates or soy protein isolates can also be obtained from defatted soy flour or defatted soy flakes, while texturized soy proteins are obtained from soy meal or from soy concentrates or soy protein isolates.
Interesting facts about the properties and durability
The color of soybean oil depends on the production method. Thus oil obtained through pressing is light yellow to yellow, while oil obtained through extraction features a brownish yellow tinge. Soybean oil possesses a pungent, greenish-musty and nutty scent that is described as pleasant. The taste is considered mild and also pleasant. The flashpoint is around 350°C; the melting point, around -16 to -8°C. Soybean oil is comprised of around 14% saturated fatty acids (especially palmitic and stearic acids), about 24% monounsaturated fatty acids (especially oleic acid), and ca. 62% polyunsaturated fatty acids (especially linoleic and linolenic acids). This high omega-3 and omega-6 content, especially in cold-pressed soybean oil, has a beneficial effect on nutrition. Additionally, the oil contains tocopherols (4 forms of vitamin E), phytosterols, and a relatively high lecithin content of about 1.5-3.5%. Unopened and stored in a cool, dark place, the oil has a shelf life of about 9 months.
Versatile use of soybean oil
Healthy benefits in medicine and pharmacy
According to the “Lexikon der pflanzlichen Fette und Öle”, soybean oil can be used in various ways in the fields of medicine and pharmacy. Natural soybean oil has a high lecithin content (approx. 3%). Due to the high proportion of unsaturated fatty acids, especially omega-3 fatty acid linolenic acid, soybean oil is said to have a positive effect in reducing the risk of heart disease. This oil is also used in dermatology to treat skin diseases.
Technical and industrial use
The paint industry uses soybean oil as a quick-drying oil, primarily for the production of paints, varnishes, printing inks, paints and fillers. Soybean oil is also used in the production of biodiesel.
The fatty acids contained in soybean oil are also used in cosmetics and body care products, serve as the basis for bath oils and creams and are used in essential oils and geranium oils.
Soybean oil – the power for your kitchen
In nutrition, soybean oil is considered one of the most important and most frequently used plant oils. It serves not only as salad oil, but can also be used as baking fat. What is more, it is used in the manufacture of margarine and mayonnaise and is also contained in numerous convenience foods as part of the plant oils. It also serves to help improve the volume of baked goods and delay staleness; as well as improve both the flow property of chocolate and the dissolvability of instant products.In natural medicine.
Soybeans protect against many diseases
In folk medicine, soybean oil is used for treating various regions of the body: stomach and intestines, heart and circulatory system, and the immune system. Yet soybeans are not pressed into oil solely for the purposes listed above, but rather, most especially to obtain soy press cake and soy extraction meal, which arise as by-products during the pressing or extraction. These can be processed into high quality, protein-rich feed and into various other soy protein products (for example, soy flour, foods containing soy, soy protein isolates, soy concentrates, textured soy protein, etc.). Here, the less oil that remains in the press cake or soy meal after pressing, the higher the protein content, and the better the press cake or soy meal is.
In addition to their own knowledge acquired through press trials, the following sources were used to create the article:
- Öle, natürlich kaltgepresst, Basiswissen & Rezepte, Marcus Hartmann, Hädecke, 2008
- Heilende Öle, Pflanzenöle als Nahrungs- und Heilmittel, Neue Erkenntnisse, Günter Albert Ulmer Verlag Tuningen
- Lexikon der pflanzlichen Fette und Öle, Krist, Buchbauer, Klausberger, SpringerWienNewYork, 2008
- www.wikipedia.de
- en.wikipedia.org
