Soybeans lecithin from

Figure 4. (a) Planar bilayer membrane system for single-channel currents measurement. Soybean lecithin in n-decane was applied to a hole separating two aqueous chambers. Chambers were filled with metal chloride salt at pH 7.2. The voltage was applied to the outer cell with respect to the inner. The currents across the bilayer were recorded on a PCM recorder through a patch-clamp amplifier and a lowpass filter, (b) Typical records of current observed at -t-50.0 mV (symmetrical 0.5 M solution). Currents increase upward from the zero level shown by the dotted line in each panel. 

The unsaturated phospholipid from soybean lecithin also shows a similar effect, while the unsaturated phospholipids from red blood cell membranes, although showing a slight effect of cholesterol interaction, still show a prominent polymethylene peak in the high resolution spectrum. 

As an example of an asymmetric membrane integrated protein, the ATP synthetase complex (ATPase from Rhodospirillum Rubrum) was incorporated in liposomes of the polymerizable sulfolipid (22)24). The protein consists of a hydrophobic membrane integrated part (F0) and a water soluble moiety (Ft) carrying the catalytic site of the enzyme. The isolated ATP synthetase complex is almost completely inactive. Activity is substantially increased in the presence of a variety of amphiphiles, such as natural phospholipids and detergents. The presence of a bilayer structure is not a necessary condition for enhanced activity. Using soybean lecithin or diacetylenic sulfolipid (22) the maximal enzymatic activity is obtained at 500 lipid molecules/enzyme molecule. With soybean lecithin, the ATPase activity is increased 8-fold compared to a 5-fold increase in the presence of (22). There is a remarkable difference in ATPase activity depending on the liposome preparation technique (Fig. 41). If ATPase is incorporated in-... 

Unilamellar liposomes of 500-600 A diameter from soybean lecithin. 

C Hanras, JL Perrin. Gram-scale preparative HPLC of phospholipids from soybean lecithins. J Am Oil ChemSoc 68 804-808, 1991. 

Our previous GC analyses of the transmethylated phosphatides from this material, commercial soybean "lecithin," have shown 54% linoleic acid and 5% linolenic acid. The material designated soybean "lecithin" of course contains not only phosphatidylcholine, but also substantial amounts of phosphatidylethanolamine, phos-phatidylinositol, and phosphatidic acid. Both of the latter would confer a substantial negative charge to the microdisperse particles. 

Nature utilizes surfactants for a variety of additional roles. A natural surfactant, using a strict definition, is a surfactant taken directly from a natural source (isolated by a separation procedure from either a plant or an animal origin).42 Lecithin, obtained either from soybean or from egg yolk, is probably the best example of a truly natural surfactant. Other natural originated surfactants are the various soap-like surfactants for the removal of fatty/oily substances. These compounds produce a rich lather when dispersed into water and are found in various natural systems (such as chestnuts, in leaves and seeds of Saponaria Officinalis (soapwort), in the bark of the South American soaptree Quillaja saponaria Molina and in the fruits of Acacia Auriculiformis (Figure 7.2) 43,44... 

The use of surfactants in the food industry has been known for centuries. Naturally occurring surfactants such as lecithin from egg yolk or soybean and various proteins from milk are used for the preparation of many food products, such as mayonnaise, salad creams, dressing, and desserts. Polar lipids such as monoglycerides have been introduced as emulsifiers for food products. More recently, synthetic surfactants such as sorbitan esters (Spans) and their ethoxylates (Tweens), sucrose esters, have been used in food emulsions. It should be mentioned that the structures of many food emulsions is complex, and in... 

Alternatively, the enzyme may be used in an encapsulated form. Chen and Chang (1993) showed that hydrolysis of milk fat by lipase from Candida cyclindracea encapsulated in reverse micelles formed by soybean lecithin in isooctane, could be manipulated to favor the release of short-chain fatty acids by using a higher concentration of enzyme and a higher ratio of water to surfactant concentration at 45°C. 

Supercritical CO2 extraction also has been used to selectively extract phosphatidylcholine from de-oiled soybean lecithin (197). The effects of temperature, pressure, and amount of ethanol on phosphatidylcholine extraction were examined, and a high-purity product could be produced with optimized conditions. 

Standard-grade, commercial lecithin from the soybean is a complex mixture. It comprises phospholipids, triglycerides, and minor amounts of other constituents (i.e., phytoglycolipids, phytosterols, tocopherols, and fatty acids). The composition and molecular arrangement of this heterogeneous mixture of compounds defines a product that is low in apparent polarity and has a strong tendency to promote water-in-oil (w/o)-type emulsions (31). 

The ensuing section is a brief review of phospholipid plant sources other than those from the soybean, which have current or potential commercial applications. Soybean lecithin then will be discussed in more detail later throughout the subsequent sections in this chapter. 

Both the glycolipids and the phospholipids of corn have lower percentages of linolenic acid (18 3) and are more saturated than those in the soybean. In general, cmde corn and soybean lecithins are equal in linoleic acid (18 2) content, but lino-leic acid in corn varies from 42% to 70% depending on the variety of corn. Phytic acid, 88% of which is in the com germ, is extracted as part of the lecithin fraction (32, 37). Elimination of phytic acid in com is desirable because it binds zinc, magnesium, and calcium. 

Solvent-extracted rapeseed oil has been found to contain the highest level of phosphorus. For this reason, it is common practice to degum solvent-extracted oil or the mixed crude oil from pressing and subsequent solvent-extraction. As the double-zero rapeseed varieties such as canola became available, the applications of rapeseed lecithin have developed positively. Where at first rapeseed lecithin was applied as an emulsifier and energy component in animal feed, the recent concerns about GMO soybean varieties in some parts of the world have increased the market value of the softseed lecithins for food applications (45). The phospholipid composition is similar to soybean lecithin with variations due to crop and processing conditions. The rapeseed phospholipid compositions in Table 12 have been confirmed by recent data, whereas the soybean lecithin composition in... 

Soybean oil contains 1.5-3.0% phospholipids (71). Crude soybean lecithin has an oil content of about 30%. PC is present at a level of about 16%., PE about 14%, and inositol phospholipids about 12% (7). As can be seen in Table 18 (8), the fatty acid compositions of soybean phospholipids are rich in polyunsaturated fatty acids. Miscellaneous low-level constituents include water, phosphatidic acid, pigments, galactosyl glycerides, various glycolipids, phosphatidylserine, carbohydrates, sterols, and tocopherols. Phosphorus content of crude soybean oil extracted from flours can vary depending on extraction temperature and flour moisture (72). 

The partial synthesis may involve several synthetic steps, depending on the basic phospholipid used, the enzyme, the final product desired, and the type and position of the phospholipid constituents to be exchanged. For example, the partial synthesis may avail of the reacylation of 3-5 -glycerophosphorylcholine (GPC). Alternatively, by a deacylation step, GPC can be obtained from PC in soybean lecithin (75). 

Commercial soybean lecithin is obtained in the traditional manner by hexane extraction of the crude oil from the soybean flake and then water degumming the... 

The total acetone insolubles content of commercial acetylated lecithin products can vary from about 52% to about 97%, the remainder being soybean oil (or another food-grade triglyceride or fatty acid as a natural constituent or added diluent), natural pigments, sterols, and other minor constituents present in crude lecithin from the soybean. The acetylated lecithin meets all the compositional requirements of the U.S. Food Chemicals Codex (54). 

Nutritional and health-related applications. Lecithin has long been known in the worldwide nutritional community. Dietary supplement lecithin is generally derived from soybean lecithin. Because of its composition of various phospholipids, vitamins, and fatty acids, lecithin is involved in numerous physiological actions that... 

Lecithin has some catalytic or cocatalytic effects in multiphase systems because of its surface-active properties. Lecithin is reported to be useful as an emulsifier in the curing of aqueous dispersions of unsaturated polyesters (337). The products are more easily removed from their molds and have improved mechanical properties when lecithin is used. In a fermentation application, 1.5% soybean lecithin acts as an inducer in the preparation of cholesterol esterase using a strain of Pseudomonas bacteria (338). Aside from its role as a catalyst, initiator, or modifier, lecithin may have ancillary uses in catalyst systems as part of a protective coating (339). 

The major lecithin sold domestically in commercial quantities is extracted from soybeans. Com and sunflower seed lecithins are available in limited amounts. Canola is being reviewed as a lecithin source in countries that do not grow significant quantities of soybeans. Lecithins may be added to feeds in cmde or refined forms, remain as residuals in solvent- or mechanical-extracted oilseed meals, be returned to oilseed meals as extracted gums or soapstocks at combined solvent extraction-oil refinery operations, or simply be native to an oilseed fed whole. 

Lecithins are essential components of cell membranes and, in principle, may be obtained from a wide variety of living matter. In practice, however, lecithins are usually obtained from vegetable products such as soybean, peanut, cottonseed, sunflower, rapeseed, corn, or groundnut oils. Soybean lecithin is the most commercially important vegetable lecithin. Lecithin... 

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