Lecithin phospholipid content

Hydrogen bonding and electrostatic interactions between the sample molecules and the phospholipid bilayer membranes are thought to play a key role in the transport of such solute molecules. When dilute 2% phospholipid in alkane is used in the artificial membrane [25,556], the effect of hydrogen bonding and electrostatic effects may be underestimated. We thus explored the effects of higher phospholipid content in alkane solutions. Egg and soy lecithins were selected for this purpose, since multicomponent mixtures such as model 11.0 are very costly, even at levels of 2% wt/vol in dodecane. The costs of components in 74% wt/vol (see below) levels would have been prohibitive. 

In practice, commercial lecithin products are not marketed by phospholipid content, but rather by a set of unique chemical and physical properties. These properties, as indicated by product specihcations, must be understood because they are used to characterize specihc lecithin types. 

Fluidizing. Fluidizing additives such as soybean oil, fatty acids, or calcium chloride can be added to adjust the viscosity. The viscosity of dried crude lecithin can also be decreased by warming it to a maximum of 60°C. The dried crude lecithin product (unbleached or bleached) can also be used to prepare a variety of grades of lecithin by removing the oil to increase the phospholipid content, or by separating the oil-free lecithin into alcohol-soluble and alcohol-insoluble fractions. 

Producing de-oiled lecithins. De-oiled lecithin represents a special category where high phospholipid content (above 95% Al) is required. When contacted with acetone, phospholipids precipitate as a fine, free-flowing powder. After removing the acetone, de-oiled lecithins are dry powders or granules (33). 

Antonis (A3) has estimated phospholipids by a procedure for determining fatty acids. This technique requires a total serum extract and a phospholipid-free extract for the measurement of both total and free fatty acids, the difference between them being a measure of the phospholipid content. Free fatty acids (A4) are determined on a phospholipid-free extract by a procedure based on partitioning the fatty acids as copper soaps into chloroform, and subsequent photometric determination of the copper with diethyldithiocarbamate. Phospholipids, as well as the free fatty acids present in the total lipid-extract, are measured by the same method, since they also form a complex with copper that is soluble in chloroform. A criticism of this technique is that equal response is not given by dipalmitoyl lecithin, dipalmitoyl cephalin, or beef brain sphingomyelin. 

Crude soya bean oil contains 3% phospholipids with about 35% of this in the form of lecithin (phosphatidyl choline) (10.47). Rapeseed oil contains 2% and Sunflower seed oil -1.5% total phospholipids. Palm oil, another large tonnage edible oil, usually contains hardly any. Phospholipids are present in margarine where they contribute to its special properties (see above). The small phospholipid content of cereal starch is responsible for its function as a crumb softener when added to bread (see below). 

Commercial soya bean lecithin is a complex mixture of phosphatides and triglycerides with minor amounts of fatty acids, sterols and other organic compounds, and with a total phospholipid content of 65-70%. (Crude soya bean lecithin contains 50% phospholipids.) The most common phosphatide components are phosphatidyl choline (-12%), phosphatidyl ethanolamine (-10%) and phosphatidyl inositol (-9%) (10.46). There is a distribution of carbon chain lengths with palmitic... 

Quantitative chemical analysis of chain phosphates and other P compounds can be carried out with automated P NMR. [85] The impurities in commercial sodinm triphosphate, Na5P30,o, can be estimated with an accnracy and precision comparable to that attained with chromatographic techniques. [86] In addition, P NMR can be nsed to estimate ATP in milk, sediment and in other bio samples. The phospholipid content of soyabean lecithin can also be determined. 

Degumming is a treatment with water (steam), which is mainly carried out with oils of high phospholipid content, e.g., soybean oil.(- lecithin). Alkali-refining is used to eliminate ffa. Almost all edible oils are processed in continuous plants today. The added NaOH forms salts, and the soap-stock ( foots ) is separated in a centrifuge from the oil, which is then washed and dried. Soapstock is a low-cost, valuable source for fatty acids. Steam-refining is done to remove the ffa by steam- distillation. 

Total phospholipid content of soybean lecithin can be obtained by solid phase extraction on silica. Lipids are eluted with 20 80 hexane/ethyl ether, then phospholipids are eluted with methanol. The amount of each fraction is determined gravimetrically after solvent removal (31). 

Figures 7.31a-c clearly show that after some critical soy content in dodecane, Pe values decrease with increasing soy, for both sink and sinkless conditions. [This is not due to a neglect of membrane retention, as partly may be the case in Fig. 7.23 permeabilities here have been calculated with Eq. (7.21).] Section 7.6 discusses the Kubinyi bilinear model (Fig. 7.19d) in terms of a three-compartment system water, oil of moderate lipophilicity, and oil of high lipophilicity. Since lipo-some(phospholipid)-water partition coefficients (Chapter 5) are generally higher than alkane-water partition coefficients (Chapter 4) for drug-like molecules, soy lecithin may be assumed to be more lipophilic than dodecane. It appears that the increase in soy concentration in dodecane can be treated by the Kubinyi analysis. In the original analysis [23], two different lipid phases are selected at a fixed ratio (e.g., Fig. 7.20), and different molecules are picked over a range of lipophilicities.

In the bile cholesterol is kept soluble by fats, phospholipids like lecithin and by bile acids. The important bile acids in human bile are cholic acid, chen-odeoxycholic acid or chenodiol and ursodeoxycholic acid or ursodiol. Bile acids increase bile production. Dehydrocholic acid, a semisynthetic cholate is especially active in this respect. It stimulates the production of bile of low specific gravity and is therefore called a hydrocholeretic drug. Chenodiol and ursodiol but not cholic acid decrease the cholesterol content of bile by reducing cholesterol production and cholesterol secretion. Ursodiol also decreases cholesterol reabsorption. By these actions chenodiol and ursodiol are able to decrease the formation of cholesterolic gallstones and they can promote their dissolution. 

There are six common grades of lecithin available including fractionated lecithins. Fractions with different phosphatidylcholine content are commercially available. Besides these common commercial grades, more special products are available, e g., enzymatically modified lecithin and phospholipids, semisynlhelic phospholipids, and acetylaled lecithins. 

The phospholipids are biodegradable, but their presence m streams and water resources, especially in the form of soap stock, is undesirable. Fatly acid recovery from phospholipids is less than with neutral oils because of the lower fatty acid content. There are no known health hazards involved in the production of commercial lecithin from crude vegetable oils because the phospholipids are nonvolatile and are a nonirritaling food material. 

In all our linewidth studies the width of the central peak was measured—i.e., the linewidth obeying Equation lib. In Ref. 45 we reported 23Na linewidth studies on a lamellar mesophase containing egg-yolk lecithin. The effect of cholesterol on the linewidth was investigated, and we found that with increasing cholesterol content in the phospholipid bilayers a marked reduction in the linewidth was observed. In accordance with similar investigations for simple soap-alcohol-water lamellar mesophases (42, 43) this is interpreted as a partial release of... 

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