The linseed oil production line is often divided into pressed linseed oil and leached linseed oil according to different processing techniques. The pressing method mainly uses mechanical external force to squeeze and extract linseed oil, while the leaching method uses the principle of solvent extraction to dissolve and extract oil from the oilseed to obtain linseed oil.
Process characteristics of linseed oil production line:
Avoiding high-temperature distillation deodorization effectively prevents the damage of polyunsaturated fatty acids – α – linolenic acid in linseed oil caused by high temperatures, effectively preserving the natural and complete nutritional components, making it easier for the human body to absorb and supplement nutrients.
Avoid harmful substances caused by the degradation of oils, sugars, and protein denaturation during high-temperature pressing.
Avoiding the darkening of linseed oil color and the appearance of burnt flavor caused by high temperature.
After multiple filtration processes, direct contact and secondary pollution of chemical substances and active ingredients caused by sulfuric acid degumming, caustic soda deacidification, and activated clay decolorization processes in the hot pressing process are avoided.
The Best linseed Oil Processing Method
linseed oil contains an adequate amount of linolenic acid and the oil is usually extracted by low-temperature physical squeezing in the linseed oil production line. Because linseed oil has a balanced proportion of linolenic acid and linoleic acid, which is 1:4, and it is scientifically proven that when the ratio of linolenic acid to linoleic acid is 1:4, the human body can be in the healthiest state, and it is very difficult for various external bacteria to invade. linseed oil can meet human health standards.
However, linolenic acid is highly heat-sensitive and easily oxidized. When the critical temperature is exceeded, the activity of linolenic acid begins to be destroyed. Therefore, when making flax seed oil, it is necessary to choose the physical pressing method at low temperature without any heating treatment. Low-temperature physical squeezing retains the activity of linolenic acid, and no additives in the whole process to maintain the natural quality of raw materials. Second, the physical pressing temperature is lower than the melting point temperature of the wax, so that the pressed linseed oil is free from the “dewaxing” procedure and avoids the damage caused by the dewaxing process.
Processing Steps of Flaxseed Oil Physical Press Line
The pressing production process keeps the most effective ingredients in flaxseed, such as polyunsaturated fatty acids, protein, dietary fiber, vitamins, trace elements and so on. The pressed oil is more suitable for a special supplement for human health. Normal temperature pressing method refers to the flaxseed oil extraction at room temperature under great pressure from physical machinery without the traditional process of high-temperature frying or steaming, so the normal temperature pressed oil still distributes in the undeformed protein cells and contains rich ingredients (linolenic acid and other nutrients).
The steps of flaxseed oil press line are mainly: Flaxseed selecting → screening → cleaning up impurities → crushing → flaking → conditioning →normal temperature pressing → residue separation → degumming →dehydrating → debittering → crystallization → cryogenic filtration → physical pressed linseed
Material selecting
Due to the unique production technology of normal temperature pressed linseed oil, the requirements for raw materials are more stringent, therefore, fresh and plump flax seeds should be selected. The acid value of oil produced by immature and aged grains is higher and the flavor is poor, while mildew and broken grains are liable to be polluted by aflatoxin, so immature, damaged, mildewed and aged grains cannot be used to produce flaxseed oil. In addition, the following indicators should also be controlled: oil≥32%, moisture≤9%, impurities≤2%, acid value (KOH)≤1.0mg/g, peroxide value≤5mmol.
At present, the commonly used raw materials for pressing flaxseed contains 38%~45% of oil and 6.5%~8.5% of moisture
Cleaning & sorting
In order to reduce the wear of the equipment in the follow-up process, to increase the oil yield, to avoid the deepening of the color of the crude oil, to avoid the increase of sediment content and the smelting consumption, the cleaning process is equipped with 1 unit high efficient cleaning destoner screen with functions of wind collection, screening & stone removing and 1 unit magnetic separator for removing the impurities such as dust, shell, stem and leaf, mud block, sand, stone, metal and so on in the raw materials. After cleaning, the flax seed has high cleanliness, the impurity content in seeds are less than 0.15% and the seeds content in the leftover are less than 1.5%.
Crushing
After cleaning, the pure material is still a whole seed and its shell is hard, which is not good for squeezing out oil and must be broken. A YF1 roller oil mill is selected and the crushed material has smaller granularity which 70% of the granules could be sifted through 20 mesh screen.
Flaking
The purpose of the flaking is to destroy the organization cells of the oilseed, increase the surface area of the flaxseed, shorten the distance of the oil flowing, and facilitate the extraction of the oil. The requirement of the rolling billet is that the billet is thin and uniform, the powder size is small, and there is no oil leakage. Therefore, a hydraulic rolling machine is used in the flaking process, and the machine has a smooth and easy operation, flexible and reliable performance, strong operability and other advantages. The flake thickness after rolling is generally 0.25~0.35mm.
Conditioning
The purpose of conditioning is to adjust the moisture content of the flaxseed material. According to the characteristics of flaxseed flake and cold press machine, the suitable moisture content is about 7%~8%. Too high and too low moisture content is not conducive to the extraction of oil, and the conditioning process is generally carried out in the conditioning pot.
Normal temperature pressed oil generally refers to the vegetable oil which is squeezed under the condition of room temperature. In the pressing process, SZY type screw oil press is specially selected, this machine is specially designed with a large theoretical compression ratio, so the oil can be pressed and expanded many times in the press chamber to realize the strong pressing, and the oil yield is high in one press.
Please note: The moisture of flaxseed cold pressing is≤8%, the residual oil of the pressed cake is≤8.5%, and the oil outlet temperature is 42℃~55℃.
The crude oil extracted from the oil press contains a large amount of oil residue, which should be separated before refining. The crude oil is firstly passed through the oil scraper into the oil tank for preliminary oil residue separation. The separated oil is then pumped into the blade filter for filtering, and then the filtered oil would be sent to the refining workshop for refining. The type of blade filter is vertical blade filter and horizontal filter.
Hydration degumming process uses hydrophilicity of colloidal impurities such as phospholipid to absorb water, expand, agglomerate and separate. First, the cold pressed crude oil is injected into the hydration tank and a certain amount of hot water is added under the condition of stirring, which causes the colloidal impurities such as phospholipids absorb water and expand, the specific gravity increases, and the precipitate separates. After the hydration reaction is finished and settled for a period of time, the oil, residue and wastewater are separated. The hydrated oil is then fed into the dehydration tank for vacuum dehydrating.
The squeezed flaxseed oil has a lot of substances precipitated in the pressing process, such as flavonoids, saponin, etc. These components have high activity and bitter taste, so it is necessary to debitter the cold pressed oil. Debittering conditions are as follows: Under the oil temperature of 60~65℃ and the vacuum degree of 90~100kpa, the active carbon adsorbent is quickly added to the oil and the stirring speed is 60~80r/min. The reaction time is around 20~40min. After the reaction is finished, cool the oil to room temperature, and the flax seed oil is obtained after the vacuum filtration. Debittering process uses all physical processes to improve the flavor of flax seed oil and keep the original nutrition of flaxseed oil.
Wax is an inherent ingredient in oil. The wax content of flax seed oil is generally 2%~3%. Wax can reduce the transparency of oil and affect the color of oil under the condition of low temperature, so it is necessary to dewaxing flax seed oil. Oil dewaxing is a process in which the high melting point wax&solid fat contained in the oil are separated from oil by cooling and crystallization and then are removed by filtration or centrifugation.
After dehydration and debittering, the oil first enters into a rapid crystallizer to be rapidly cooled until the wax crystal nucleus are partly precipitated, and then enters into a crystallizing tank. In order to increase the probability of aggregation and collision between the precipitated wax particles, and make the oil evenly cooled, the oil in crystallizing tank needs to be properly stirred. In order to continue the crystallization of the wax and make the small crystal particles continue to grow, when the oil is cooled to 15℃, the stirring is stopped and the oil continues to be cooled down to 5℃. The total crystal growing time is about 72 hours (the specific crystal growth time and temperature are determined by the quality of the oil and actual production conditions). The oil that has reached the crystallization time can be sent to filtration to obtain pure flaxseed pressed oil.
The purpose of refining linseed oil
All components in oils and fats, except for triglycerides, are called impurities.
The purpose of refining is to remove impurities, maintain the biological properties of oils and fats, and retain or extract useful substances. In fact, refining does not remove all impurities, but selectively removes impurities.
According to the composition and properties of impurities in crude oil, it can be divided into three categories:
(1) Insoluble solid impurities, such as sediment, cake powder, fibers, clay, catalysts, etc.
(2) Colloidal impurities such as free fatty acids, sterols, vitamin E, pigments, vitamins, gossypol, etc.
(3) Volatile impurities, such as water, alcohols, hydrocarbon solvents, odorous substances, etc.
Most impurities are detrimental to the quality and storage of oil, such as moisture not only affecting the transparency of oil but also promoting its hydrolysis and rancidity; Free fatty acids affect flavor and accelerate oil degradation; Phospholipids can make oils and fats turbid, and when heated, they can produce black sediment, bubbles, bitterness, etc; Various pigments directly affect oil color and can also promote oil rancidity; The presence of colloids, sulfur-containing and phosphorus compounds, soap feet, heavy metal salts, etc. makes it difficult for subsequent processes such as stripping and deacidification.
What equipment is needed for processing linseed oil
The equipment for processing linseed oil varies depending on the production capacity of the oil factory. Oil mills process linseed oil with small output, limited space and budget. Purchasing major equipment such as oil presses, frying pans, and filters can meet the production needs of oil mills. If the budget is sufficient, a small set of refined oil equipment can also be purchased to improve the quality of linseed oil.
For small and medium-sized edible oil processing plants, the site and budget are relatively sufficient, and there are also requirements for production capacity, which requires the use of a complete set of linseed oil production lines. The complete production line first needs to clean, remove stones, roll embryos, steam fry and other pretreatment of linseeds, and then press and extract oil to obtain pressed linseed oil.
For edible oil processing plants with large output, the process of pressing first and then leaching can be adopted. After pressing and extracting linseed oil, the residual oil rate in the cake is high. Using pre pressing and leaching technology can not only obtain high-quality crude oil, but also reduce the residual oil rate in linseed cake to 1%, improve oil yield and cake quality, and create higher benefits for oil factories. The pre pressing extraction process requires not only a pre pressing oil press, but also a complete set of extraction equipment.