The sunflower, or common sunflower, belongs to the sunflower genus and family Asteraceae. Depending on the source, there are up to 65 species, but only the plant species of the sunflower, lat. Helianthus annuus L., is important for oil production. It is an annual cultivated plant, which prefers warm and sunny locations. The sun exposure is directly related to the growth height and yield of the plants.
The plant is a 1-3m high herbaceous plant, which has a strong, branched and slightly rough-haired stem. It prefers nutrient-rich soil with adequate water supply. The leaves of the sunflower are usually alternate on the stem and the petals are arranged in a circle. The leaves are heart-shaped, hairy, stalked and strongly toothed at the edge. The flower heads can grow between 15-40cm tall with their colorful tubular flowers. Only during the growing phase the plant turns its leaves and bud with the sun (from east to west). During the night, the plant turns back to its original position. This is also called heliotropism, which is the ability of parts of the plant to move with the sun. In the case of the sunflower, the sun's rays do not seem to be the decisive factor directly, but rather a circadian rhythm. If the flowers are fertilized by insects, the plant stops its daily movement and remains with the flower head facing east.
According to literature, the sunflower comes from North America and was already used there three to four millennia ago for oil extraction. Thus it was cultivated by the Indians long before the discovery of North America. It probably came to Europe with the Spanish and began its triumphal march around the world in the 16th century. The largest cultivation areas in the world are in Russia, Ukraine and Argentina.
Depending on the variety, the sowing depth and sowing width are different. Typical indicators are: Seed depth 3-6cm with a seed spacing of 20-45cm and a row spacing of 35-70cm. Protection with pesticides is usually carried out only in the growth phase, because here there is still competition with weeds. After the so-called row closure, i.e. the time when neighboring plant rows touch each other, weeds can no longer grow due to the lack of sunlight. A common pest is the so-called sunflower rust. This fungus attacks the leaves of sunflowers and causes high yield loss.
The flowering period is from June to October, depending on the growing area. The decisive factor is the grain moisture, which should not exceed 19%, otherwise there is a risk of microbial decay later on. The plant is dead at harvest, as evidenced by a yellow-colored basket underside and gray leaves/stems. Harvesting is fully automated with specially converted combines that separate the kernels from the plant. The remaining straw remains in the field and serves as fertilizer.
Up to 2000 seed kernels can be harvested from one flower head of a plant. These are on average 1cm long and up to 0.8cm wide. The color is black, black and white longitudinally striped or white, depending on the variety. The outer leathery shell can be easily separated from the oily seed.
In the cold pressing process, after harvesting, the seeds are cleaned, ground and, if necessary, peeled. The resulting pulp is then pressed at temperatures below 40 degrees Celsius: the oil obtained is of high quality and has a light yellow color after filtering. During this process, waxes contained in the shell are also pressed out. These may cause the oil to become cloudy at low temperatures, but this is not an indication of spoilage or contamination. If the seeds are hulled, this cloudiness does not occur.
The hot pressing process is similar to the cold pressing process with hulled seeds: with the addition of heat, the yield can be further increased, and the oil takes on a reddish-yellow color as the temperature increases.
The third form of oil extraction is the extraction of the pulp with solvents or supercritical gases. This is the process with the highest yield: by means of extraction of solvents (lipophilic substances such as ethanol) or supercritical gases such as carbon dioxide, almost all the oil can be removed from the seed. Since unwanted substances are also extracted from the seeds here, the oil still needs to be refined. The final product is clear and has a light yellow color.
Depending on the area of application, the oil can be further refined in order to precisely adjust the desired properties such as ingredients. In this process, substances can be removed from or added to the oil.
The edible oil is almost odorless and has a pleasant taste. Depending on the production method, the oils can be stored in a cool, dry place and protected from light for 9-12 months.
Depending on the growing area, variety and corresponding refinement, the oil can be divided into different classes. Here, the proportion of fatty acids contained is decisive for the naming. The following oils with abbreviations are known: Sunflower oil (SO) with high linoleic acid content (HL), oleic acid content (HO), palmitic-linolenic acid content (HP/HL), palmitic and oleic acid content (HP/HO) and stearic and oleic acid content (HS/HO).
With the discovery of a mutant in Russia, the cultivation of a variety with high oleic acid content became possible. The oleic acid content could thus be increased from an average of 20% to over 80%. At the same time, linoleic acid decreased from an average of 60% to 15%. Linoleic acid tends to oxidize quickly, which greatly reduces the life of the oil. HO oils can therefore be stored longer and are also more heat stable due to the fatty acids they contain. As described above, there are a variety of other sunflower seed oils, although only HO and normal sunflower seed oil play a role in everyday life.
Normal sunflower oil has a high linoleic acid content and is therefore classified as a slow-drying oil (semi-drying). In the cosmetics industry it is therefore often used for oily skin, as it dries out the skin easily. Due to its high oleic acid content, HO oil can be used for massage/ treatment of dry skin, as it does not dry out the skin, unlike the usual sunflower seed or peanut oil.
Cold-pressed sunflower seed oil is used as cooking oil in the kitchen and can be processed into various products (including salad dressings, mayonnaise and margarine). Here, mostly only HO oils are used, as they are said to have a healthier effect.
The hot-pressed oil is usually further refined or processed only in the industrial. Refined oil can be processed in many areas of industry due to its adjusted ingredients. Thus, the oil can be an ingredient in the varnishes, paints and leather products.
Due to its high oleic acid content, HO oil is more heat stable than normal sunflower seed oil and can therefore be used for frying and deep-frying food. The fatty acids it contains ensure low oxidation with atmospheric oxygen. As a result, the oil only becomes rancid slowly and can thus increase the service life of a deep fryer. If the oleic acid content is increased even further (>90%), the oil is also used as a lubricating, hydraulic or special oil. In addition to having the same or even better chemical properties than conventional mineral oil-based products, this oil is biodegradable. The classic application is in construction machinery in hydraulic engineering, where biodegradability of lubricants is mandatory.
Sunflower seed oil can also serve as a filler in pharmaceutical products, as well as a substitute for olive or peanut oil. In folk medicine, the oil is still used for constipation, psoriasis or rheumatism (external application).
Sunflowers are often deliberately planted as marginal or flowering strips near corn fields. Here they are intended to provide new habitat for insects that can better pollinate the crops (mostly monocultures).
In China, sunflower seed oil is called "joy oil" for pregnant women, as it is said to have a positive influence on the unborn child. In folk medicine, the oil is also said to have an influence in cases of reduced fertility.
Sunflower seeds are especially popular in Russia, where they are processed into desserts or eaten pure.