Vegetable lecithins processing

Vegetable lecithins are obtained as a by-product in the vegetable oil refining process. Polar lipids are extracted with hexane and, after removal of the solvent, a crude vegetable oil is obtained. Lecithin is then removed from the crude oil by water extraction. Following drying, the lecithin may be further purified. ... 

The purpose of this work, therefore, was to evaluate the effect of several SPE, lecithins, and SPE-lecithin mixtures on the crystallization of fat and to determine the one that accelerated the crystallization in the vegetable-ghee processing, thus reducing the tempering time. 

Only a minor proportion of the total lecithin that is potentially available in the vegetable processing industry is produced. If the phosphoHpids are not to be made into commercial lecithin, they may be left in the cmde oil or, if they are to be separated from the cmde oil as wet gum, they may be mixed into soybean meal for animal feed. 

Sometimes natural fine chemicals are by-products in bulk products refining. Examples are (a) lecithin and steroids in vegetable oil refining (b) betaine, pectin and raffinose in sugar manufacture (c) quinic acid in quinine extraction of the bark of Cinchona trees (d) chitin and the red pigment asthaxanthin in lobster and shrimp processing and (e) lanolin, lanosterol and cholesterol in sheep wool purification. 

In commercial formulations, phospholipids are not available as pure products. Mostly they are obtained as a by-product of the process of refining vegetable oils, during the so-called degum-ming step (3,4), from which a liquid-to-pasty product is obtained that is referred to as lecithin. Lecithin contains about 65% phospholipids plus about 30% residual neutral lipids and minor amounts of glycolipids. For historical reasons, most commercially available lecithins are derived from soybean oil, but lecithins of other oils could be used as well. From this discussion it follows that the determination and quantification of phospholipids is of importance both to control how efficiently the phospholipids have been removed from vegetable oils and to control the quality of the lecithin. For this purpose it is important to know not only the total amount of phospholipids but also the amount of the different types of phospholipids present, because it is well known that the functional properties of the various phospholipids differ widely (2-8). 

With egg lecithin, a different manufacturing process must be used since the lecithin in egg yolks is more tightly bound to proteins than in vegetable sources. Egg lecithin is thus obtained by solvent extraction from liquid egg yolks using acetone or from freeze-dried egg yolks using ethanol (95%). ... 

Glycerophospholipids (PL) are abundant lipid components found in Nature [1]. Most vegetable oils, fish oil and egg yolk are particularly rich in mixtures of phospholipids. They are characterized by the presence of a polar head and two fatty acid chains in the apolar part of the molecule. The two acyl chains mainly consist of saturated fatty acid residues in the snl position and mainly (poly)unsaturated fatty acid chains in the sn2 position. Mixtures of phospholipids at low cost are obtained from the degumming process of vegetable oils. Lecithin, the main component of the mixture, has the polar head characterized by the choline residue. It is usually defined as phosphatidyl choline (PC) and it is understood that the composition of the apolar part is composed of mixtures of fatty acid residues dependent to a large extent on the source of the raw material (fatty acid chains composition of PC from soy beans palmitic 11.6%, stearic 3.4%, oleic 4.6%, linoleic 66.4%, linolenic 8.7%). Scheme 1 shows a PC with two defined acyl chains at the glycerol backbone l-palmitoyl-2-linoleoyl-5n-glycero-3-phosphocholine (PLPC). 

In conventional chemical processing of vegetable oils, crude oil is recovered from the mechanically expressed vegetable seed by solvent extraction using hexane, as shown in Figure 3.14 [22]. The misceUa (a mixture of extracted oil and solvent) from the extractor contains 60—70% solvent, which is recovered by distillation and reused. Purification of crude oil consists of removing components that are harmful and are not wanted in the final product, the pure oil. These components are phosphatides (gums and lecithin). 

Processes and products developed to produce industrial materials from renewable resources have been too numerous to record here. For competitive reasons — supply of raw materials and technical and economic considerations — some of the products have varied widely in industrial use. Major U.S. industrial consumption of renewable resources have recently included oils and fats (animal and vegetable) industrial alcohol (wheat, corn, grain sorghum) fibers (cotton lint, flax, hides and skins) paper (forest products) isolated proteins (milk casein, animal glues, soybean, corn) turpentine and rosin (naval stores) and other chemicals (monosodiiim glutamate--wheat starch and dextrin—corn lactose—milk molasses and pulp residues --sugarcane and beet tannin lecithin pectin furfural). 

Lecithin could be produced from any crude vegetable oil, but because of the huge quantities of soybean grown and processed, and because of the relatively high percentage of phosphatides in soybean oil, practically in the world soybean oil is the principal commercial source of natural and modified lecithins as well. The world s consumption of lecithin is estimated at 100,000 tons per year. In western Europe 30,000 tons are produced and more than the half of it is applied as modified lecithins / 7. In Hungary sunflower is the major oilseed crop, on this account sunflower lecithin has been the subject of this study. 

Glycerophospholipids are important components of biological membranes and are thus widely spread in nature. Partially purified products are used for a variety of applications, with soya lecithin as a typical example. Enzymes can be used to modify glycerophospholipids in various ways and in the surfactant area removal of one of the fatty acids to make lysophospholipids is the most important example. Sometimes this reaction is carried out only to make it easier to remove the phospholipids fraction from the neutral fat, such as in the processing of vegetable oils. This enzymatic de-gumming is an important industrial process [20]. In other applications, lysophospholipids are produced in order to improve the emulsifying properties of the lipids. One such example is in the preparation of mayonnaise, with improved emulsion stability [21]. In this application, phospholipase A2 is used selectively to remove the fatty acid in the sn-2 position. 

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