Lecithin and Other Phospholipids

Surfactants frvm Renewable Resources Edited by Mikael Kjellin and Ingeg d Johansson 2010 John Wiley Sons, Ltd 

Sourcing of identity preserved (IP) non-GMO (genetically modified organism) soya lecithin for the European food market has changed drastically the lecithin world market supply system since 1996. Traditional non-GMO soya beans availability wiU become scarcer, which presents a market opportunity for high-quality IP soya, sunflower and rapeseed lecithins. 

Lecithin processing is performed in four subsequent unit operations. 

One to three percent of water is mixed thoroughly with the oil at 50-70 °C. The phospholipids hydrate within 1 hour to form a gum with a higher specific density than the oil. The easily hydratable phospholipids are PC, PI and LPC. PE and PA have low hydrating properties and are therefore marked as nonhydratable phospholipids (NHPs). In practice a mix of these various phospholipids is separated in the lecithin gum. After this water degumming process, sometimes enzymatic degumming is applied for hydrolysing the NHP with phospholipase-A enzymes into hydrophilic lysophosphatidylethanolamine 

In Latin America and other continents batch driers are used, claiming that investments are low and that the drying at a maximum of 90 °C is efficient for lecithin with good colour. The De Smet type batch drier is made of a horizontal cylindrical jacketed body with a dome. Hot water circulates in the jacket. A heavy duty, rotating coil mounted on a shaft provides the necessary heat, while at the same time it agitates the lecithin gums. 

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LECITHIN. Lecithin and other phospholipids are of universal occurrence in liv ing organisms. They are constituents of biological membranes and are involved in permeability, oxidative phosphorylation, phagocytosis, and chemical and electrical excitation. 

CigH3202, Mr 280.45, mp. -5.0 to -5.2°C, bp. 229-230°C (1.6 kPa) soluble in organic solvents. L. is an essential fatty acid occurring as glycerol esters in practically all natural fats and oils (see table) the recommended daily uptake for an adult ca. 10 g. On account of its vitamin characteristics L. together with some other multiply unsaturated fatty acids used to be called vitamin F. L. was first isolated from linseed oil (/ini o/eum) Linum usitatissimum). Lecithins and other phospholipids are often especially rich in lino-leic acid. In animal organisms L. is converted by the introduction of two further double bonds and chain ex-... 

Figure 26.12 shows a space-filling model of a lecithin (a phosphatidylcholine). Lecithin and other phospholipids are elongated, almost rodlike molecules, with the nonpolar (hydrophobic) hydrocarbon chains lying roughly parallel to one another and the polar (hydrophilic) phosphoric ester group pointing in the opposite direction. 

Lecithin and Other Phospholipids. These compounds act as bonds between fats and proteins in cell membranes, and in the special lipoproteins which carry cholesterol and fats (triglycerides) in the blood. They also promote the absorption of fatty substances in the intestine. For example, it is believed that the high rate of absorption of cholesterol from eggs is due in part to the lecithin which is present in the egg yolk. 

Phospholipides.— Lecithin and other phospholipides of the diet are important nutritional somces of choUne and of phosphoric acid, and are resolved into their components by the esterases of the small intestine previous to absorption. Within the intestinal mucosa, a re-synthesis occiun, or a new phospholipide is assembled containing units derived from the saponified fats of the diet, and as such participates in the lipide transport in the lymph and the portal blood. By use of a phosphate containing a radioactive isotope of phosphorus as indicator, Artom and his colleagues (1937) have shown that phospholipides of the lecithin and cephalin type are synthesised in large quantities during fat absorption, and accumulate in the intestinal mucosa, the liver, and to a lesser extent, the kidney, but not in the spleen, heart or skeletal muscles. 

Figure 9.14 The simple addition of a minimal amount of water to a hydrocarbon solution of lecithin (or other phospholipids) brings about the formation of an organogel. (Adapted from Scartazzini and Luisi, 1988.)...

Cationic surfactants are bactericidal agents and are used as antiseptics and disinfectants in topical and other external preparations and are never used in parenterals. Lecithins and other natural phospholipids, as one of the main constituents... 

The phospholipases hydrolyze lecithin, cephalin, and other phospholipids. The products of the hydrolysis vary according to the bonds which are attacked, but only two phospholipases will be discussed here. The reader is referred to Zeller s review for a complete discussion of these enzymes. 

Consider also more highly purified lecithin and other purified forms of phospholipid concentrates from oilseeds. Isolating a more purified form of lecithin using SC-CO2 may increase the price dramatically when compared to a lower quality product. Nutraceutical-grade phospholipids (i.e., concentrated phosphatidylcholine or phosphatidylserine) concentrated using SC-CO2 may conunand prices of US 1500/ lb in certain markets. Such economic incentives could easily justify investment of the SC-CO2 plant and equipment. 

As has been established in other chapters of this book, the reasons behind the search for bio-based alternatives to petroleum-based surfactants can be summarized in one word - sustainability. However, there are different ways to produce bio-based surfactants, all of which have different degrees of sustainability. As an example, soaps - alkaline salts of fatty acids - can be considered bio-based surfactants, as they are derived from the saponification of triglycerides obtained from plants and animals. Methyl ester sulfonates are obtained from fatty acid methyl esters (FAMEs) which in turn are also obtained from triglycerides found in plants and animal tissues. Lecithin, lysolectihins and other phospholipids can also be extracted from plant and animal tissue. As will be explained in the next sections, bio-based surfactants can also be secreted by microbial cultures fed with specific substrates. 

In addition to phenolic substances, there are other components present in foods which have no antioxidant activity of their own, but which increase that of phenolic antioxidants. They are called synergists, and they should be accounted for in any discussion of antioxidant activity. Polyvalent organic acids, amino acids, phospholipids (lecithin) and various chelating agents belong to this group. Proteins may modify the efficiency of antioxidants as they react with the reaction products of both antioxidants and synergists. 

T6. The Action of Phospholipases The venom of the Eastern diamondback rattler and the Indian cobra contains phospholipase A2, which catalyzes the hydrolysis of fatty acids at the C-2 position of glycerophospholipids. The phospholipid breakdown product of this reaction is lysolecithin (lecithin is phosphatidylcholine). At high concentrations, this and other lysophospholipids act as detergents, dissolving the membranes of erythrocytes and lysing the cells. Extensive hemolysis may be life-threatening. 

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). 

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