Description
Food-grade lecithin is obtained from soybeans and other plantsources. It is a complex mixture of acetone-insoluble phosphatides that consists chiefly of phosphatidyl choline, phosphatidyl etha nolamine, and phosphatidyl inositol, combined with various amounts of other substances such as triglycerides, fatty acids, and carbohydrates. Refined grades of lecithin may contain any of these components in varying proportions and combinations depending on the type of fractionation used. In its oil-free form, the prepon-derance of triglycerides and fatty acids is removed and the product contains 90% or more of phosphatides representing all or certain fractions of the total phosphatide complex. The consistency of both natural grades and refined grades of lecithin may vary from plastic to fluid, depending upon free fatty acid and oil content, and upon the presence or absence of other diluents. Its color varies from light yellow to brown, depending on the source, on crop variations, and on whether it is bleached or unbleached. It is odorless or has a characteristic, slight nutlike odor and a bland taste. Edible diluents, such as cocoa butter and vegetable oils, often replace soybean oil to improve functional and flavor characteris tics. Lecithin is only partially soluble in water, but it readily hydrates to form emulsions. The oil-free phosphatides are soluble in fatty acids, but are practically insoluble in fixed oils. When all phosphatide fractions are present, lecithin is partially soluble in alcohol and practically insoluble in acetone.
Chemical Properties
Lecithins vary greatly in their physical form, from viscoussemiliquids to powders, depending upon the free fatty acid content.They may also vary in color from brown to light yellow, dependingupon whether they are bleached or unbleached or on the degree ofpurity. When they are exposed to air, rapid oxidation occurs, alsoresulting in a dark yellow or brown color.
Lecithins have practically no odor. Those derived from vegetablesources have a bland or nutlike taste, similar to that of soybean oil.
Occurrence
Lecithin is found in foods such as eggs, beef liver, and peanuts. Commercial sources are available
Uses
Lecithin is an emulsifier that is a mixture of phosphatides which are typically surface-active. it is now commercially obtained from soy-beans; previously it was obtained from egg yolk. it is used in marga-rine as an emulsifier and antispatter agent; in chocolate manufacture it controls flow properties by reducing viscosity and reducing the cocoa butter content from 3 to 5%; it is used as a wetting agent in cocoa powder, fillings, and beverage powders; an antisticking agent in griddling fat; and in baked goods to assist the shortening mix with other dough ingredients and to stabilize air cells. typical usage levels range from 0.1 to 1.0%.
Uses
egg lecithin is emollient and particularly recommended for sensitive skin.
Uses
lecithin is a natural emollient, emulsifier, anti-oxidant, and spreading agent, lecithin is a hydrophilic ingredient that attracts water and acts as a moisturizer. generally obtained for cosmetic products from eggs and soybeans, it is found in all living organisms.
Uses
Edible and digestible surfactant and emulsifier of natural origin. Used in margarine, chocolate and in the food industry in general. In pharmaceuticals and cosmetics. Many other industrial uses, e.g. treating leather and textiles.
Uses
lecithin (hydrogenated) is an emulsifier.
Production Methods
Lecithins are essential components of cell membranes and, inprinciple, may be obtained from a wide variety of living matter. Inpractice, however, lecithins are usually obtained from vegetableproducts such as soybean, peanut, cottonseed, sunflower, rapeseed,corn, or groundnut oils. Soybean lecithin is the most commerciallyimportant vegetable lecithin. Lecithin obtained from eggs is alsocommercially important and was the first lecithin to be discovered.
Vegetable lecithins are obtained as a by-product in the vegetableoil refining process. Polar lipids are extracted with hexane and, afterremoval of the solvent, a crude vegetable oil is obtained. Lecithin isthen removed from the crude oil by water extraction. Followingdrying, the lecithin may be further purified.
With egg lecithin, a different manufacturing process must beused since the lecithin in egg yolks is more tightly bound to proteinsthan in vegetable sources. Egg lecithin is thus obtained by solventextraction from liquid egg yolks using acetone or from freeze-driedegg yolks using ethanol (95%).
Synthetic lecithins may also be produced.
Definition
ChEBI: A glycerophosphocholine compound having O-acyl substituents at both the 1- and 2-positions of the glycerol. It is a major constituent of cell membranes.
Pharmaceutical Applications
Lecithins are used in a wide variety of pharmaceutical applications. They are also used in cosmetics and food products.
Lecithins are mainly used in pharmaceutical products asdispersing, emulsifying, and stabilizing agents, and are included inintramuscular and intravenous injections, parenteral nutritionformulations, and topical products such as creams and ointments.
Lecithins are also used in suppository bases, to reduce thebrittleness of suppositories, and have been investigated for theirabsorption-enhancing properties in an intranasal insulin formulation. Lecithins are also commonly used as a component of enteraland parenteral nutrition formulations.
There is evidence that phosphatidylcholine (a major componentof lecithin) is important as a nutritional supplement to fetal andinfant development. Furthermore, choline is a required componentof FDA-approved infant formulas. Other studies have indicatedthat lecithin can protect against alcohol cirrhosis of the liver, lowerserum cholesterol levels, and improve mental and physicalperformance.
Liposomes in which lecithin is included as a component of thebilayer have been used to encapsulate drug substances; theirpotential as novel delivery systems has been investigated. Thisapplication generally requires purified lecithins combined in specificproportions.
Therapeutically, lecithin and derivatives have been used as apulmonary surfactant in the treatment of neonatal respiratorydistress syndrome.
Biochem/physiol Actions
It also acts as a source of lipid messengers/ bioactive lipids including: lysophosphatidylcholine, diacylglycerol, phosphatidic acid, lysophosphatidylcholine, arachidonic acid and platelet activating factor. Phosphatidylcholine is produced in the liver by the CDP-choline (cytidine diphosphocholine) pathway.
Side effects
Lecithin may be safe when used as a supplement at a maximum dose of 30 grams per day for up to 6 weeks. It may have side effects, including diarrhoea, nausea, stomach pain or a feeling of fullness. When applied to the skin: Lecithin is probably safe for most adults. When used medicinally or as a drug carrier, no related serious adverse reactions have been reported.
Safety
Lecithin is a component of cell membranes and is thereforeconsumed as a normal part of the diet. Although excessiveconsumption may be harmful, it is highly biocompatible and oraldoses of up to 80 g daily have been used therapeutically in thetreatment of tardive dyskinesia. When used in topical formulations,lecithin is generally regarded as a nonirritant and nonsensitizingmaterial. The Cosmetic Ingredients Review Expert Panel(CIR) has reviewed lecithin and issued a tentative report revising thesafe concentration of the material from 1.95% to 15.0% in rinse-offand leave-in products. They note, however, that there areinsufficient data to rule on products that are likely to be inhaled.
storage
Lecithins decompose at extreme pH. They are also hygroscopic andsubject to microbial degradation. When heated, lecithins oxidize,darken, and decompose. Temperatures of 160–180°C will causedegradation within 24 hours.
Fluid or waxy lecithin grades should be stored at roomtemperature or above; temperatures below 10°C may causeseparation.
All lecithin grades should be stored in well-closed containersprotected from light and oxidation. Purified solid lecithins shouldbe stored in tightly closed containers at subfreezing temperatures.
Purification Methods
Lecithin from hen egg white is purified by solvent extraction and chromatography on alumina. It is suspended in H2O and kept frozen until required [Lee & Hunt J Am Chem Soc 106 7411 1984, Singleton et al. J Am Oil Chem Soc 42 53 1965]. For purification of commercial egg lecithin, see Pangborn [J Biol Chem 188 471 1951].
Incompatibilities
Incompatible with esterases owing to hydrolysis.
Regulatory Status
GRAS listed. Accepted for use as a food additive in Europe.Included in the FDA Inactive Ingredients Database (inhalations; IMand IV injections; otic preparations; oral capsules, suspensions andtablets; rectal, topical, and vaginal preparations). Included innonparenteral and parenteral medicines licensed in the UK.Included in the Canadian List of Acceptable Non-medicinalIngredients.
