The production of sunflower oil consists of many operations during which complex physical and chemical processes occur in the raw material. A simplified schematic diagram of the processing of oil sunflower raw material is shown in the diagram:
Oil raw material → removal of impurities, drying and grinding → mixture of sunflower kernel pulp → separation of husk from kernel → grinding (flattening kernel) → and husk moistening, heating, drying pulp → pressing pulp → oil → oil filtration.
BY CRUSHING THE SUNFLOWER OIL SEEDS KERNEL
By grinding the sunflower kernel to extract the oil, it is necessary to destroy their cellular structure. The result of the grinding operation is to convert the oil contained in the seed cells into a form available for further technological operations. The grinding process is carried out with precision and reliability using five-roll machines of the VS-5 brand, which are specifically designed for this purpose. The sunflower seed kernel is ground in 4 passes through roller machines. The quality of the ground sunflower kernel is significantly influenced by the moisture content. The structure of the kernel cells is optimally destroyed at a moisture content of 5.5-6%, underscoring the importance of maintaining this level for high-quality oil production.
The material obtained after grinding is called pulp, which is characterized by a significant specific surface. It cannot be stored for a long time, because cell enzymes (lipase) quickly decompose fats,
hydrolyzing them into glycerol and free fatty acids, which worsens the quality of the Ukraine sunflower oil. Aside from the destruction of cell membranes, the structure of the oil-containing part of the cell is also disrupted during grinding. A significant part of the crude sunflower oil is released and adsorbed on the surface of the pulp particles. The Ukraine sunflower oil in the pulp is distributed in the form of thin films on the surface of the crushed kernel or seed particles and is held on it by the forces of molecular interaction, the magnitude of which exceeds the pressure created by presses for squeezing oil. To reduce the forces that bind the oil to the surface of the pulp, a moist-thermal treatment is used, which is called roasting. This treatment is carried out in special devices known as roasters. The product obtained after moist-thermal treatment is called pulp. In industry, two types of roasting are known: wet and dry. Each method has its own advantages and is used based on the specific requirements of the production process.
THE WET ROASTING OF SUNFLOWER OILSEEDS
The wet roasting of sunflower oilseeds, a process that demands precision and care, is carried out in two stages. The first stage, a crucial preparatory phase, involves moistening and heating the oilseeds with the addition of water, after which it is steamed, bringing its moisture content and temperature to optimal values. This sets the stage for the second stage, where the moistened sunflower oilseeds are dried, i.e. conditioned, to provide the necessary structure for better pressing.
THE DRY ROASTING OF SUNFLOWER OILSEEDS
Dry roasting consists of drying and heating the pulp to a certain temperature without prior heating and humidification. The combined action of moisture, heat and oxygen during roasting contributes to the inactivation of the enzyme system of the pulp, which contributes to the intensive course of hydrolytic and oxidative processes. Therefore, before dry roasting, enzymes in the pulp are inactivated in steaming screws by intensive and short-term heating to 80-85ºС with simultaneous humidification. Humidification and roasting of the pulp at oil mills are carried out in special roasters, which are divided into three types by design: vat, screw and drum. The pulp from the sunflower kernel when pressed once on double-action presses MP-21 after grinding enters the steaming-humidifying screw, where it is moistened with steam to a humidity of 8-9% and heated to a temperature of 80-85ºС. The moistened pulp is dried in a roaster, bringing the moisture content in it to 2-1.5%, and the temperature to 115-120ºС, the roasting time is 40-45 minutes. In world practice, there are two methods of oil production: mechanical
or pressing and the method of dissolving the oil in volatile organic solvents, or extraction. In the production of vegetable oils, these two methods are used separately or together.
THE SUNFLOWER OIL EXTRACTION BY PRESSING
The seedsoil is adsorbed in the form of thin films on the surface of the pulp particles, held on the surface by significant surface forces. For effective oil removal, this bond must be weakened. For this purpose, hydrothermal (moisture-heat treatment) is used – pulp production. This technological operation is called frying. HTP (hydrothermal treatment) affects the quantity and quality of the final products: oil, cake and meal. When moistening and subsequent heat treatment of the pulp, the bond of lipids with the non-lipid part of the seed – proteins and carbohydrates – is weakened and the oil becomes relatively free. Then the pulp is heated to higher temperatures, the viscosity of the oil decreases noticeably, at the same time the moisture content in the pulp decreases, partial denaturation of proteins occurs, which changes the plastic properties of the pulp and partial inactivation of hydrolytic and oxidative enzymes of the seeds, which worsens the quality of the oil. After the WTO, the pulp turns into pulp. Previously, hydraulic presses were used, the disadvantage of which was insufficiently complete removal of oil, as a result of which its content in the meal was 7-8%. Modern plants use screw presses, the main working elements of which are the screw shaft and the seer cylinder. Depending on the pressure created in the seer space on the material being pressed, as well as on the oil content remaining in the meal, oil mills use different types of screw presses. By purpose, they are divided into presses for preliminary oil separation (prepress), deep or final oil separation presses (expellers) and double-action presses (preliminary and final oil separation is carried out in one unit). The pressure at the beginning of pressing is 0.03 MPa and at the cake outlet – 0.35 MPa. The duration of the material’s stay in the press (duration of pressing) depends on the shaft rotation speed, the size of the outlet gap, the physical and mechanical properties of the material, etc. Screw presses, depending on the pressure on the material being pressed and the oiliness of the material, are divided into presses for preliminary (shallow) oil removal (prepress) and presses for final (deep) oil removal.
THE EXTRACTION METHOD OF OIL EXTRACTION
The extraction method of sunflower oil extraction can be used both in its pure form and in combination with the forpress method. An example of the extraction method of oil extraction in its pure form is the direct extraction of “raw pulp” during processing. For the extraction of sunflower oil from sunflower seeds, the forpressing scheme is used, i.e. shallow oil presses are used at the first stage. In sunflwer oil refineries, gasoline is used as a solvent to remove oil by the extraction method, and in recent years, a butane-propane mixture, which is gaseous under normal conditions. After forpressing, the cake is sent for extraction for the final extraction of oil. To increase the contact surface between the solvent and the crushed raw material (cake grits), the latter is passed through a paired flattening roller with smooth rollers and plates with a thickness of 0.2-0.4 mm are obtained. There are two options for extracting oil by the extraction method – infusion and sequential degreasing. During infusion, the material is poured with a solvent. After some time, the oil passes into the solvent and a solution (message) is formed, which is then poured. The degreased material is again poured with a clean solvent and this is repeated until almost all the oil is extracted. In the extraction process, two periods are distinguished: 1) extraction of free oil, that is, that which is contained on the outer and inner surfaces; 292) extraction of oil contained in intact or partially deformed cells. After the end of the extraction, the meal contains approximately 1% oil and about 40% solvent. The message obtained after extraction consists of volatile solvent, oil and solid particles. To remove the solid fraction from it and separate it into oil and solvent, the particles of the solid fraction are separated from the micelle by settling, centrifugation or filtration. Of the three main methods for separating heterogeneous systems, the filtration method is most often used. To distill the volatile solvent from the micelle, the distillation method is also used, using special distillation units for this. First, the micelle is heated in a distiller with steam to a temperature of 100-105ºС. At the same time, part of the gasoline evaporates and the oil concentration increases to 75-85%. After that, the micelle enters the final distiller, where the gasoline is completely distilled with steam at a temperature of 210-220ºС. The oil formed in the final distiller is removed from it, cooled with water in a heat exchanger, weighed and sent to a storage facility from which it is sent for purification. Currently, the extraction method of oil production at factories in the country is the leading one, as it provides a higher oil yield than when using the pressing method.
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