Lecithins acetone-insoluble

Commercial lecithin is insoluble but infinitely dispersible in water. Treatment with water dissolves small amounts of its decomposition products and adsorbed or coacervated substances, eg, carbohydrates and salts, especially in the presence of ethanol. However, a small percentage of water dissolves or disperses in melted lecithin to form an imbibition. Lecithin forms imbibitions or absorbates with other solvents, eg, alcohols, glycols, esters, ketones, ethers, solutions of almost any organic and inorganic substance, and acetone. It is remarkable that the classic precipitant for phosphoHpids, eg, acetone, dissolves in melted lecithin readily to form a thin, uniform imbibition. Imbibition often is used to bring a reactant in intimate contact with lecithin in the preparation of lecithin derivatives. 

The US. Pharmacopeia (USP XXII) or National Formula (NFXVII) (20) also provide a similar description however, the peroxide value is not defined (Table 9). These specifications are also given in the Handbook of Pharmaceutical Excipients (HPE), pubhshed jointiy by the American Pharmaceutical Association and The Pharmaceutical Society of Great Britain (21), which defines lecithins both from plants and eggs. The Merck Index (22) specifies a slightiy lower acid value. The Japanese Monograph (ISCI-II) (23) specifies a slightiy lower acetone-insoluble matter and a lower heavy-metal content. 

The standard methods (26) of analysis for commercial lecithin, as embodied in the Official and Tentative Methods of the American Oil Chemists Society (AOCS), generally are used in the technical evaluation of lecithin (27). Eor example, the AOCS Ja 4-46 method determines the acetone-insoluble matter under the conditions of the test, free from sand, meal, and other petroleum ether-insoluble material. The phosphoHpids are included in the acetone-insoluble fraction. The substances insoluble in hexane are determined by method AOCS Ja 3-87. 

Commercial lecithin is produced by water degumming (precipitation from oil with ion-exchange treated water), separation by stacked disk centrifuge, and vacuum drying to less than 1 percent moisture content. Crude lecithins contain 70-72 percent acetone insolubles (AI) and are standardized to 62-64 percent and an acid value of 30 by addition of oil and fatty acids before sale. Crude lecithins may be treated with acetone to obtain free-flowing powders with 95-98 percent AI. Lecithin can be additionally purified, bleached, fractionated, hydrogenated, hydrox-ylated, acetylated, sulfonated, and halo-genated.104 One domestic company makes 13 kinds of lecithin for food uses alone. 

It is a complex mixture of acetone-insoluble phosphatides that consists chiefly of phosphatidyl choline, phosphatidyl ethanolamine, 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 preponderance of triglycerides and fatty acids is removed and the product contains 90% or more of phosphatides representing ah or certain fractions of the total phosphatide complex. Edible diluents, such as cocoa butter and vegetable oils, often replace soybean oil to improve functional and flavor characteristics. Lecithin is only partially soluble in water, but it readily hydrates to form emulsions. The oil-free phosphatides are soluble in fatty acids, but they are practically insoluble in fixed oils. When ah phosphatide fractions are present, Lecithin is partially soluble in alcohol and practically insoluble in acetone. 

AI. The amount of acetone-insoluble matter (%A1) is a measure of the polar material found in lecithin. In soybean lecithin, the acetone-insolubles typically contain 70-75% phospholipids, with the remaining portion consisting of glycolipids, carbohydrates, and a small amount of residual triglyceride oil. The amount of acetone-insoluble matter is determined by the AOCS Official Method Ja-4-46 (77). 

AS/. The AV is the number of milligrams of potassium hydroxide necessary to neutralize the acids in 1 g of lecithin (62). A product s AV is representative of the acidity contributed by both the phospholipids and any free fatty acids that are present. The AV is usually not indicative of pH, as the chemical nature of the phospholipid imparts buffering quahties to most systems. Lecithins typically exhibit a neutral pH value in aqueous media. An AV above 36 may indicate degradation of the lecithin because of improper processing or substandard quality soybeans. AV should not be confused with free fatty acid content, pH, or mineral acids. The correct method to assay for free fatty acids is to titrate only the acetone-soluble portion of the lecithin, whereby any contribution from the phospholipids in the acetone-insoluble portion is eliminated. AV is determined by the AOCS Official Method Ja 6-55 (77). 

Consistency. Lecithins are available in both fluid and plastic (solid) forms. Fluid lecithins generally follow Newtonian flow characteristics. The viscosity profile of lecithins is a complex function of acetone-insoluble content, moisture, mineral content, acid value, and the combined effects of assorted additives such as vegetable oils and surfactants. Generally, higher AI and/or moisture content yields higher viscosity, whereas an increased AV often decreases viscosity. Certain divalent minerals, such as calcium and others, can also adjust the viscosity level. 

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). 

The USPNF 23 describes lecithin as a complex mixture of acetone-insoluble phosphatides that consists chiefly of phosphatidylcholine, phosphatidylethanolamine, phosphatidylser-ine, and phosphatidylinositol, combined with various amounts of other substances such as triglycerides, fatty acids, and carbohydrates as separated from a crude vegetable oil source. 

NOTE.—Ether dissolves hum egg-yolk, in addition to lecithin, some fat and protein. The protein and a part of the fat are removed by extracting the residue from ether with alcohol. The lecithin is finally separated by adding acetone to an etheral solution of the lecithin and fat. The latter is soluble in acetone while the lecithin is insoluble. 

Lecithin, a mixture of phosphatidyl choline, phosphaddyl ethanolamine, and phosphatidyl inositol, is used as a surfactant in many food, pharmaceutical, and cosmetic products. Lecithin is a product of soy bean oil degumming operations. It is obtained from the hexane extract of flaked soy beans which contains the seed oil and a portion of the phosphatides that are initially present in the soy bean membrane. The exhact is seated with water at 80 °C, and the phosphatides are hydrated rendering them oil insoluble which makes it easy to filler them from the oil. This oil insoluble fraction is termed cmde lecithin and consists of about 70% phosphatides and 30% oil. De-oiled lecithin is obtained by treating the cmde lecithin with acetone. Lecithin is insoluble in acetone and the oil is, and a separation into a 90 to 9r phosphatides fraction can be achieved quite readily. The prior... 

The lecithins are insoluble in water, in which they swell up, but they are soluble in alcohol and ether although insoluble in acetone. 

Acetone-insoluble (AI). The amount of AI matter (%AI) is the approximate indication for the amount of phospholipids, glycolipids and carbohydrates, because the oil and fatty acids dissolve in acetone. In crude lecithin AI is synonymous with activity, i.e. functional or nutritional properties. The AI is a commercial and legal specification. However, with NMR and HPLC the more exact amount and composition of true phospholipids can be analysed. 

HBX-1 Analytical Procedure. Pristera (Ref) briefly describes its analysis as follows Extract TNT wax and lecithin with carbon tetrachloride then determine TNT by titanous reduction as described on p 466 of Ref extract with water the Ca chloride from carbon tetrachloride insoluble residue and extract RDX, with hot toluene, from water-insol residue using Wiley extractor. Extract NC from toluene-insol residue with cyclohexanone, acetone, or tetrahydrofuran the remainder is A1... 

Lecithin is a polar lipid, the definition being that it is a lipid that is insoluble in acetone. It is one of a whole class of phospholipids, which tend to be found in the membranes of animals and also in plants. 

Soybean lecithin is the predominant source of food and pharmaceutical lecithin because of its availability and outstanding functionality. The composition of crude soy lecithin is shown in Table 14. As a result of the presence of a large amount of neutral oil, crude lecithin is usually de-oiled to improve its functionality. De-oiling is based on the solubility difference of neutral and polar lipids in acetone, in which the phospholipids are precipitated and separated. Alcohol fractionation of de-oiled lecithin can further separate lecithin into an alcohol-soluble fraction that is enriched with phosphatidylcholine and an alcohol-insoluble fraction enriched with phospha-... 

Sunflower lecithin is not produced in considerable amounts worldwide. This is mainly because of the low lecithin content of crude sunflower oil as compared with 2.9% for soybean, 1.9% for canola, 2.4% for cottonseed, and 2.0-2.7% for com oil (normalized at 70% of insolubles in acetone). Lecithin removal from sunflower oil may be justified in strong sunflower producer countries. It may be used as a food additive in view of its high phosphatidylcholine and essential fatty acid content. Upon refining and fractioning stages, the quality of sunflower lecithin may be improved for the manufacture of food products and cosmetics. 

A commercial, nearly oil-free lecithin is prepared by acetone extraction of natural lecithin, which removes all but 2-4% oil and free fatty acids. Then an optional alcohol fractionation step can separate the oil-free lecithin into an alcohol-soluble lecithin enriched in phosphatidylcholine and an alcohol-insoluble fraction enriched in phosphatidylinositol. The choline fraction is an excellent emulsifier for oil-in-water (o/w) emulsions and the inositol fraction for water-in-oil (w/o) emulsions. 

Soybean lecithin is soluble in aliphatic and aromatic hydrocarbon solvents, partially soluble in ethyl alcohol (principally the inositol fraction), and practically insoluble in acetone (less than 0.003% weight/volume at 5°C) and in water (73). When mixed with water, soybean lecithin hydrates to a thick emulsion that can be thinned with water to almost any desired dilution. Acetone does dissolve readily in lecithin and will form a thin, uniform imbibition as long as the quantity of acetone is insufficient to precipitate the phospholipids. Lecithin is soluble in... 

Sample preparation followed the method described by Ryoto (13). One gram SPE or dry deoiled lecithin was dissolved in 100 g of oil and heated to 60-80°C for complete dispersion of the emulsifier. Ethanol-insoluble lecithin was added at a level of 1 mg/100 g oil and any residual to the ethanol was removed by heating a water bath. Samples with 0.5 and 0.25% SPE or dry lecithin were prepared by diluting the original sample with oil. Deoiling and fractionation of lecithin were done with acetone and ethanol, respectively, as reported by Ziegelitz (15). Turbidity test was conducted on 70 mL oil in a 100-mL tube at different concentrations of DK F-10 (0.0,0.5, and 1.0%) at several temperatures. 

Properties Yellowish, amorphous substance characteristic odor and taste. Insoluble in water and acetone soluble in chloroform and ether slightly soluble in alcohol. A group of phospholipids in which two fatty acids (Rt and R2) form ester linkages with the two hydroxyl groups of glycerophosphoric acid, and either ethanolamine or serine (Rj) forms an ester linkage with the phosphate group. Cephalins are therefore either phosphatidylethanolamine or phosphatidylserine. They are associated with lecithins found in brain tissue, nerve tissue, and egg yolk. 

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