The soybean, lat. Glycine max, belongs to the Fabaceae family. It grows mainly in a subtropical or tropical climate and thrives optimally at about 30 degrees Celsius. The annual plant is about 30-100cm tall and hairy on stem and leaf. The large leaves are three-toothed and hang alternately on long stems, which themselves are more or less branched.
The annual herbaceous plant forms a taproot up to 1.6m long, which is colonized by soybean-specific nodule bacteria (so-called Bradyrhizobium japonicum). The bacterium and the plant form a symbiosis, which provides the plant with a nitrogen source and thus promotes growth. The plant is thus not dependent on nitrogen from the soil.
Soybeans are categorized as short-day plants because they require a lighting period of less than 12 hours to produce a flower. If grown in a climate with long daylight hours, the formation of flowering plants is delayed, as is the maturation of seeds.
The soybean is similar in appearance to the German bush bean.
The oil content of the beans can vary depending on the variety, location and sun exposure. On average, about 20% of the dry weight of the beans can be assumed.
After harvesting, the beans are ground and mixed with water. The water makes it easier to extract the oil from the plant cells. A light yellow oil is obtained by pressing.
The remaining press cake still contains oil that could not be extracted by mechanical pressing. The press cake can be further processed using organic extractants or supercritical gases. The oil obtained from extraction then has a brownish, yellow color. The odor of the oils is reminiscent of a pungent, nutty, pleasant smell.
Depending on the application of the oils, further processing of the oils may be necessary. For example, the oil is hydrogenated for food purposes to set a desired viscosity. During hydrogenation, unsaturated fatty acids are saturated with hydrogen, which leads to a higher melting point and enables the production of margarine.
However, the double bond of the fatty acids contained can be saturated not only with hydrogen but also with oxygen. In this process, so-called epoxides are formed by chemical reaction or with the aid of enzymes, which represents a chemically reactive group in the molecule. This chemical group can then form chemical compounds with other molecules. The epoxidized soybean oil (SME; see below) obtained in this process is used exclusively in the processed industry.
Soybean oil is one of the most produced vegetable oils worldwide. Its main components are linoleic acid (approx. 50%), oleic acid (approx. 23%) and alpha-linolenic acid (approx. 8%). The latter fatty acid in particular, together with the sterols it contains, has a positive effect on the risk of arteriosclerosis and on triglyeride cholesterol levels. Its use is therefore particularly common in cooking, where it is used as margarine or vegetable oil.
Another ingredient lecithin serves as a solubilizer and is used in Respiratory Distress Syndrome in premature infants. In this disease, not enough surfactant is yet formed in the lungs, which can be compensated by lecithin. In pharmacy, soybean oil can also be used in intravenous infusions for artificial nutrition, where soy lecithin also serves as a solubilizer. In general, soybean oil and soy products seem to have a positive protective effect on colon, stomach, lung, and prostate cancers.
The oil is quickly absorbed into the skin and leaves only a small residue. The cosmetic and personal care industry uses the oil as a base for creams or bath oils, as it also protects against moisture loss. Further, the fatty acids are used as "carriers" of vitamins and fat-soluble plant ingredients.
In addition to rapeseed and palm oil, soybean oil can also be processed into biodiesel. In this process, the oil is chemically processed until it can be added to normal diesel. This is also referred to as soy methyl ester (SME). The advantage of this process is the positive energy balance, since less energy has to be invested in processing than biodiesel made from corn.
Soybean oil is often used in technology as a carrier or filler: a frequently mentioned example is the production of inks for printing print media. However, the oil can also be further chemically modified: Epoxidized soybean oil has been given its own CAS number (8013-07-8) due to its chemical reactivity and is used as an additive, stabilizer or plasticizer in various fields. These include: Coating products, fillers, putties, plasters, modeling compounds, adhesives and sealants, finger paints, polymers, and lubricants and greases.
Soybean cultivation has been criticized for years because of its carbon footprint, as the largest share is used as animal feed in livestock farming. Slash-and-burn agriculture, long transport distances and the disproportionate consumption of animal products lead to a deterioration of the environmental balance.
The soybean receives up to 40% protein, which differs little in composition from animal proteins.