Overview[1]
Lecithin, also known as phosphatidylcholine, is known as the “third nutrient” after protein and vitamins. It is the material basis of life and the basic raw material for various membrane structures of cells. It exists in every cell and is more concentrated in the liver, brain, heart, kidney and immune system. It is synthesized by the liver in the human body and is mainly found in soybeans in food. , egg yolk. Lecithin in English means “egg yolk”. Lecithin is an important anti-aging substance. It can regulate blood lipids to prevent vascular sclerosis, protect the liver, prevent Alzheimer’s disease, strengthen the brain and improve intelligence, prevent and resolve the formation of gallstones, increase the activity of cellular superoxide dismutase (SOD), enhance the ability of cells to scavenge free radicals, and reduce It produces lipid peroxide and can decompose toxins in the body. Because it is hydrophilic, it can enhance the function of hemoglobin to make the skin smooth and soft. The inositol contained in it is a basic element of skin and hair health care and can promote blood circulation. Promotes hair regeneration and inhibits hair graying. It is worthy of being an anti-aging guardian.
Physiological activity[2]
(1) Participate in cell membrane composition and improve lipid metabolism. Lecithin is the main component of biological membranes. Ingestion of lecithin can improve membrane phospholipid components, increase membrane fluidity and membrane enzyme activity. If there are too many saturated fatty acids in the fatty acid part of membrane phospholipids, the membrane will become stiff, but PC can change the saturated fatty acids of membrane phospholipids into unsaturated fatty acids, thus increasing the fluidity of the cell membrane. In addition, PC can promote the synthesis and regeneration of lipoproteins, protect the mitochondria and microsomal membranes of cells from damage, prevent the membrane structure from stabilizing cell degeneration and promote recovery, prevent intracellular enzymes from escaping to the outside of the cell, and maintain the activity of intracellular enzymes. , improve lipid metabolism abnormalities caused by illness, thereby improving various functions such as glucose metabolism and protein metabolism.
(2) As an antioxidant, it delays the aging of the body. Lecithin’s resistance to oil oxidation has been used in oil production. Tests have shown that lecithin with a content of more than 0.2% in oil can significantly improve the antioxidant effect of rapeseed oil, sunflower oil, fish oil, etc., while artificial lecithin has very low antioxidant activity in the presence of copper, iron, manganese and other ions. high. It is precisely because lecithin has antioxidant functions that it can repair damaged biofilms and delay the aging of the body. It is reported that as age increases, the body’s ability to scavenge free radicals decreases. Excessive free radicals interact with free or combined unsaturated fatty acids, causing them to continuously form lipids in the form of chain or branched chain reactions. Peroxide MDA, MDA is an extremely active cross-linking agent. It quickly cross-links with phosphatidylethanolamine to form a fluorescent pigment, and then combines with proteins, peptides, and lipids to form lamellar lipofuscin, which can compress the cell nucleus and organelles. Deformation affects the normal metabolic transmission function of neurons. Lecithin has obvious effects on maintaining the stability of the moisture content of the skin’s stratum corneum and inhibiting the formation of lipofuscin in keratinocytes.
(3) Choline supply source. Choline is a type of ammonium compound widely distributed in animals and plants. It has a variety of biological functions and is an essential nutrient for the human body. PC, the main component of lecithin, is more suitable for absorption as organic choline. According to experiments, 1 hour after ingesting PC, the concentration of choline in the blood can be 2.7 times that before ingestion. The blood can still maintain a high concentration of choline after 12 hours. Therefore, ingesting PC can increase the level of choline in the blood.
(4) Arachidonic acid supply source. AA belongs to the ω-6 series of essential fatty acids, which is closely related to the maintenance of biological functions of cell membranes. It is also the precursor of endogenous cell regulatory factors and has functions such as lowering serum cholesterol, protecting the liver, and inhibiting cancer cells. Egg yolk lecithin contains a certain amount of unsaturated fatty acids such as DHA, so silicone can provide the AA needed by patients with liver disease, infants and young children.
(5) Promote nerve conduction and improve brain vitality. Choline released after digestion of lecithin in food reacts with acetyl COA under the action of choline acetyltransferase to generate acetylcholine. Increased acetylcholine content can promote the rapid development of brain synapses, thereby increasing the speed of information transmission between nerve cells in the brain. Speed up, improve memory and learning ability. In addition, lecithin can also treat various neuroses and contribute to the recovery of epilepsy and dementia. In addition to the above functions, lecithin also has immunomodulatory and anti-tumor functions.
Preparation[2-3]
1. Solvent method
Traditional lecithin production mostly uses organic solvents for extraction, which has the advantages of large production capacity, short cycle, easy continuous operation, easy automation, relatively cheap solvent prices, and easy recycling. The principle is to use the difference in solubility of each phospholipid component in certain solvents to separate lecithin from other components. The solvents used are generally C1-C4 low-carbon alcohols, n-hexane, petroleum ether, diethyl ether, and ethyl acetate. wait.
The solubility of lecithin in low-carbon alcohol is relatively large, while the solubility of cephalin and sphingomyelin in low-carbon alcohol is small, but lecithin is insoluble in acetone. The key to the solvent extraction method is to find a good solvent or solvent system, which should have good solubility and selectivity for the target product to be extracted. The temperature, solvent dosage, solvent concentration, etc. must be controlled during extraction. Organic solvents are divided into single solvent extraction methods and mixed solvent extraction methods in terms of extraction methods. Lecithin is extracted from squid eggs using an improved solvent extraction method, with an extraction rate of more than 6%.
The process conditions for refining lecithin with ethanol were studied.�The best operating conditions are: extraction temperature is air temperature, ethanol mass concentration 0.85kg/L, extraction time 20min, pH=10.5. Secondly, they conducted chemical TG-DTA-DTG thermal analysis on the lecithin refined products and determined the crystal transition temperature zone, melting temperature, and oxidative cleavage temperature of lecithin. They found that lecithin only begins to decompose at about 320°C, and the key The break is at the phosphoryl group. Acetone is used as the solvent to extract soybean lecithin. The experimental results show that when the lecithin yield is used as the evaluation index, the optimal process conditions are: acetone deoiling temperature of 45°C, deoiling time of 1 hour; ethanol extraction temperature of 70°C, extraction time 15 minutes. The best effect of r-A12O3 on the adsorption of impurities in lecithin: the adsorption temperature is 25°C and the time is 30 minutes. The process route provided by this method is simple and easy to operate, which is extremely beneficial to the purification of soybean lecithin derived from soybean oil feet with abundant resources and low price. The lecithin yield is often higher than the value reported in the literature.
2. Column chromatography
Column chromatography uses an adsorbent as a stationary phase. When the solutes in the mobile phase pass through the stationary phase, they achieve separation due to their different adsorption and desorption abilities. Commonly used adsorbents are silica gel, alumina, diatomaceous earth, etc., and the eluent is often a mixture of several solvents such as chloroform and low-carbon alcohol. This method uses an improved organic solvent or cadmium chloride compound method to extract crude lecithin, and then uses centrifugal liquid chromatography to refine chromatographically pure lecithin. The Faure method and Bligh-Dyer column chromatography were used to prepare lecithin from chicken eggs, and the acetone precipitation method, hot pyridine separation method, and countercurrent distribution method were used to separate the phospholipid components.
3. Ultrafiltration Rohm and Haas method
The application of membrane technology in refined vegetable oils is relatively late. The separation of phospholipids began in 1977. It has developed rapidly in recent decades and has been applied on a large scale. The use of membrane technology to extract phospholipids has attracted attention, and several membranes are already available, some of which are based on the extraction of colloids from mixtures of oil and hexane; others are extracted directly from vegetable oils without organic solvents . In the first case, the main difficulty is the stability of the membrane in organic solvents, in the latter it is the high viscosity of the oil and the very low flow rate. Membrane technology has attracted the research of many chemical engineers because it does not use chemical reagents and is energy-saving. The ability of membranes to resist pollution has been greatly improved, but the permeation volume and membrane life still restrict the industrialization of membrane processes. It should also be pointed out that ultrafiltration can also effectively separate phospholipids in cooperation with other processes. For example, the process of preparing phospholipids for injection using physical and chemical methods and super technology.
4. Supercritical extraction method
Supercritical fluid extraction (SFE for short) technology is a new separation technology that emerged in the 1970s, especially the application of supercritical CO2, which opened up a new research field and became a hot spot in multi-disciplinary intersections. The operating parameters of supercritical carbon dioxide extraction are easy to control, are extremely suitable for processing heat-sensitive substances, and can produce high-quality powdered phospholipids. Supercritical fluid extraction technology uses supercritical fluids whose pressure and temperature are higher than the critical point as solvents to extract substances. The density of supercritical fluids is hundreds of times greater than that of gases, and the specific value is equivalent to that of liquids. Its viscosity is still close to that of a gas, but two orders of magnitude smaller than that of a liquid. The diffusion coefficient is between a gas and a liquid. Therefore, supercritical fluids not only have the characteristics of liquids having greater solubility to solutes, but also have the characteristics of easy diffusion and movement of gases, and the mass transfer rate is much higher than that of liquid phase processes. In other words, supercritical fluid has the properties of both gas and liquid.
