Lecithins hydroxylation

Hydroxylated lecithin. Hydrogen peroxide, in addition to bleaching, can also hydroxylate lecithin. Hydroxylation imparts hydrophilic properties, improves moisture retention, and contributes to the formation of stable oil-in-water emulsions. 

Standard-grade (crude) lecithins are excellent water-in-oil emulsifiers. However, modified lecithins can function to emulsify either water-in-oU or oil-in-water emulsions, depending on the type of lecithin modification and the specific parameters of the system. These system parameters can include pH, types of components, component ratios, solids content, and others. Unlike crude lecithins, hydroxylated lecithins are stable in acid systems (pH 3.5). Fractionated lecithins can be manufactured for specific emulsion types. As lecithin s emulsifying activity is partially dependent on its phospholipid ratio, changing the ratio can alter its emulsifying capabilities (7). 

The U.S. Standards for Identity for Margarine and Bakery Products, and Food Additive Regulations, allow the use of lecithin hydroxylated lecithin is allowed in breads without level limitations. Similarly, the use of lecithins is permitted in... 

Crude lecithin is mixed with 2-14% hydrogen peroxide and 1% lactic acid at 50-60 °C. The lactic acid reduces the pH, which facilitates the reaction. Residual water is removed by drying. During the reaction the coloured components are bleached, which yields a light coloured lecithin. Hydroxylated lecithin is superior for emulsification of oil-in-water emulsions. It easily disperses in cold and water as a whitish emulsion. This is already a good indication that the HLB value increased significantly. 

Manuf/Distrib. Hangzhou Sage Chem. Nanjing Chemlin Somerset Cosmetic Co. Trade Names Jeelan H OHIan Protalan H Ritahydrox Hydroxylated lecithin CAS 8029-76-3 EINECS/ELINCS 232-4406 Synonyms Lecithin, hydroxylated... 

Hydroxyl tion. Commercial lecithin can be hydroxylated at the unsaturated fatty acid chains by treatment with concentrated hydrogen peroxide and acids like lactic or acetic acid. 

Our present ideas about the nature of biological membranes, which are so fundamental to all biochemical processes, are based on the Singer-Nicholson mosaic model. This model of the membrane is based on a phospholipid bilayer that is, however, asymmetrical. In the outside monolayer, phosphatidylcholine (lecithin) predominates, whereas the inner monolayer on the cytoplasmic side is rich in a mixture of phos-phatidylethanolamine, phosphatidylserine, and phosphatidylinositol. Cholesterol molecules are also inserted into the bilayer, with their 3-hydroxyl group pointed toward the aqueous side. The hydrophobic fatty acid tails and the steran skeleton of cholesterol... 

This lamellar phase is formed of alternate sheets of lipid and water. The lipidic sheets containing the lecithin and the cholesterol are made of two superposed layers of oriented molecules. Each of these two monolayers is mixed and consists of lecithin and cholesterol molecules arranged side by side with their paraffinic ends turned toward the inside of the sheet and their polar groups (phosphatidyl choline group for lecithin and hydroxyl group for the cholesterol) outward—i.e., toward the adjacent sheet of water. This constitution of each of the two mono-layers forming the lipidic sheet is in conformity with the conclusion arising from the study of mixed monolayers of cholesterol and lecithin spread on the free surface of water (1). 

The infrared spectra of systems containing lactoside could not be analyzed in a similar way because the absorption of the hydroxyl groups of the sugar masked the absorptions of cholesterol at 2.8 microns and of the P-O-C group of lecithin between 8 and 10 microns. 

Liver and some intestinal cells export cholesterol into the bloodstream, together with triacylglycerols and phospholipids in the form of VLDL particles, for uptake by other tissues (see Fig. 21-1). Cholesteryl esters are formed in the ER by lecithin cholesterol acyltransferase (LCAT), an enzyme that transfers the central acyl group from phosphatidylcholine to the hydroxyl group of cholesterol.191 1913 This enzyme is also secreted by the liver and acts on free cholesterol in lipoproteins.192 Tissue acyltransferases also form cholesteryl esters from fatty acyl-CoAs.192a... 

Glycerophospholipids contain a glycerol skeleton to which two fatty acids are esterified saturated fatty acids occupy mostly sn-position 1, whereas unsaturated fatty acids are mainly present on sn-position 2. The third hydroxyl is linked to a phosphate group to which an organic base is mostly esterified (Fig. 1). The most important components of soybean lecithin are phosphatidylcholine (PC), phosphatidylethanolamine (PE), and phosphatidylinositol (PI). Phosphatidic acid (PA) may become important due to the presence of phospholipase D this enzyme slowly converts PC into PA in vegetable lecithins. Phosphatidylserine (PS), phosphatidylglycerol (PG), and lyso-phosphatidylcholine (LPC) are known as minor components lysophospholipids contain only one acyl group per molecule. Besides, ether phospholipids occur in which one or both fatty acyl... 

F. Muller-Landau and D.A. Cadenhead, Molecular packing in steroid-lecithin monolayers, Part I, Pure films of cholesterol, 3-doxyl-cholestane, 3-doxyl-17-hydroxyl-androstane, tetradecanoic acid and dipalmitoylphosphatidylcholine, Chem. Phys. Lipids 25 (1979)299-314. 

LCAT has three catalytic functions it acts as an acyltransferase (G9), a phospholipase (A25, P14), and a lysolecithin acyltransferase (S60). In this review only the acyltransferase action of LCAT will be discussed in any detail. The enzyme transfers the acyl group from the number two position of lecithin to the 3-hydroxyl group of cholesterol, resulting in the formation of cholesteryl ester and lysolecithin. 

Peroxide Value Proceed as directed under Peroxide Value in the monograph for Hydroxylated Lecithin. However, after the addition of saturated potassium iodide and mixing, mix the solution for only 1 min and begin the titration immediately instead of allowing the solution to stand for 10 min. 

HYDROXYLAMINE see HLiMSOO HYDROXYLAMINE NEUTRAL SULFATE see OLSOOO HYDROXYLAAONE SULFATE see OLSOOO HYDROXYLAMINE SULFATE (2 1) see OLSOOO HYDROXYUYWONIUM SULFATE see OLSOOO HYDROXYLATED LECITHIN see HLN700 6-HYDROXY-2-MERCAPTOPYRIMIDINE see TFR250... 

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