Lecithins consistency

Egg yolk, which contains several components with emulsifying properties, notably lecithin, is often used in all-natural , premium or homemade ice creams. Egg yolk has the approximate composition (by weight) of 50% water, 16% protein, 9% lecithin, 23% other fat, 0.3% carbohydrate and 1.7% minerals. Lecithin consists of phosphatides and phospholipids. Egg yolk is usually supplied for use in ice cream manufacture either as pasteurized fresh egg yolk, frozen sugared pasteurized egg yolk (which has had about 10% sucrose added to protect it from damage during freezing) or as dehydrated egg yolk. Egg yolk solids are normally used at about 0.5-3%. High concentrations are only used for... 

Lecithin consisting of various phospholipids including polyunsaturated fatty acid has skin softening properties in cosmetic formulations. These preparations include skin creams... 

Lecithin One of the main phospholipids found in nature with important implications in metabolism and cell membranes. Lecithin is considered an important nutraceutical compound because it lowers blood cholesterol and is key to the synthesis of choline. Chemically, lecithin is the emulsifier phosphatidyl choline, and commercial lecithin consists of a mixture of different phospholipids such as phosphatidyl ethanol amine, phosphatidyl inositol, and phosphatidyl serine. Most commercial lecithin is obtained during the refining process of soybean oil. The egg yolk is also a rich source of lecithin. Lecithin is widely used in the baking, cookie, and wheat flour tortilla industries to improve dough machinability, improve texture, and retard staling. It is generally used from 0.1%-1%. 

A typical biomembrane consists largely of amphiphilic lipids with small hydrophilic head groups and long hydrophobic fatty acid tails. These amphiphiles are insoluble in water (<10 ° mol L ) and capable of self-organization into uitrathin bilaycr lipid membranes (BLMs). Until 1977 only natural lipids, in particular phospholipids like lecithins, were believed to form spherical and related vesicular membrane structures. Intricate interactions of the head groups were supposed to be necessary for the self-organization of several ten thousands of... 

Commercial cmde lecithin is a brown to light yeUow fatty substance with a Hquid to plastic consistency. Its density is 0.97 g/mL (Uquid) and 0.5 g/mL (granule). The color is dependent on its origin, process conditions, and whether it is unbleached, bleached, or filtered. Its consistency is deterrnined chiefly by its oil, free fatty acid, and moisture content. Properly refined lecithin has practically no odor and has a bland taste. It is soluble in aflphatic and aromatic hydrocarbons, including the halogenated hydrocarbons however, it is only partially soluble in aflphatic alcohols (Table 5). Pure phosphatidylcholine is soluble in ethanol. 

The yolk is separated from the white by the vitelline membrane, and is made up of layers that can be seen upon careful examination. Egg yolk is a complex mixture of water, Hpids, and proteias. Lipid components iaclude glycerides, 66.2% phosphoUpids, 29.6% and cholesterol [57-88-5] 4.2%. The phosphohpids consist of 73% lecithin [8002 3-5] 15% cephahn [3681-36-7], and 12% other phosphohpids. Of the fatty acids, 33% are saturated and 67% unsaturated, including 42% oleic acid [112-80-1] and 7% linoleic acid [60-33-3]. Fatty acids can be changed by modifying fatty acids ia the laying feed (see... 

Hauser, H. (1987). Spontaneous vesiculation of uncharged phospholipid dispersions consisting of lecithin and lysolecithin, Chem. 

Phosphatidylcholine, commonly known as lecithin, is the most commonly occurring in natnre and consists of two fatty add moieties in each molecule. Phosphati-dylethanolamine, also known as cephahn, consists of an amine gronp that can be methylated to form other compounds. This is also one of the abundant phospholipids of animal, plant, and microbial origin. Phosphatidylserine, which has weakly acidic properties and is found in the brain tissues of mammals, is found in small amounts in microorganisms. Recent health claims indicate that phosphatidylserine can be used as a brain food for early Alzheimer s disease patients and for patients with cognitive dysfunctions. Lysophospholipids consist of only one fatty acid moiety attached either to sn-1 or sn-2 position in each molecule, and some of them are quite soluble in water. Lysophosphatidylchohne, lysophosphatidylserine, and lysophos-phatidylethanolamine are found in animal tissues in trace amounts, and they are mainly hydrolytic products of phospholipids. 

A few molecules have unexpectedly low permeability in 2% DOPC, not consistent with their octanol-water partition coefficients. Notably, metoprolol has a Pe value 10 times lower in 2% DOPC, compared to 10% egg lecithin. Also, prazosin Pe appears to be significantly lower in DOPC, compared to other lipids. 

Figure 3.6 compares iso-pH permeabilities of ketoprofen at various pH values in a 2% DOPC-dodecane model (open circles) and the 20% soy lecithin with SLS in the acceptor compartment (filled circles, data in Table 3.5). In the presence of the latter negatively charged lipids (with the make-up similar to that of BBM in Table 3.1), ketoprofen is intrinsically more permeable, by a factor of 17. The UWL limit, indicated by the solid curves in low-pH solutions, and consistent with the permeability Pu 19.8 x 10-6 cm s 1 (log Pu —4.7), masks the true intrinsic permeability of the membranes, P0. However, it is possible to deduce the membrane permeability if the pKa is known. In Fig. 3.6, the bending in the dashed (calculated) curves at pH 4 corresponds to the pKa of the molecule. Due to the UWL, the point of bending is shifted to higher pH values in the solid (measured) curves. The difference between the apparent pKa (pK 5.3 for DOPC and 6.3 for soy) and the true pKa (4.12) is the same as the difference between log P0 and log Pu [23],... 

The surfactants AOT (0.8 M) and Lecithin (0.4 M) were dissolved in isooctane. The aqueous phase, consisting of either a 10 M HAuCU solution, or alternate aliquots of 10 M HAuCU and NaBH4 (10 M), was then added to the surfactant-containing organic phase until the desired Wo (moles water/moles AOT) was reached. The reactions proceeded at room temperature. We carried out three sets of experiments to synthesize nanoparticles of different morphologies. 

When mesophase, that is, liquid crystal, consisting of three components of bile salt, lecithin and cholesterol was produced, deposition of calcium salts of bile acids was observed on the cholesterol disk surface. The relation between mesophase formation and calcification will be elucidated in this paper. 

Figure 2 The mixed micelles consisting of Bile salts and Lecithin. Disk Excess Lecithin. Sphere Excess Bile salts.

After WWII. Composition D—2 which is not an expl, but serves as an emulsifier and desensitizer of expls like HBX-1, consists of wax 84, lecithin 2 NC 14% (Vol 3 of Encycl, p C488-R) Compositions EL—387A and EL—387B, de-... 

Dispersed systems, such as emulsions, have also been employed to achieve high drug loading for parenteral administration. Emulsions generally consist of a vegetable oil (e.g., soybean), a phospholipid surfactant (e.g., lecithin), and glycerol added for isotonicity. The surfactant (emulsifier) is necessary to provide a barrier to agglomeration of the emulsion droplets. Unlike micellar solutions that are thermodynamically stable,... 

ERL Polar PE. An American plastic explosive developed by the Explosives Research Laboratory, Bruceton, Pa. It consisted of RDX (50-70% thru 30 retained on 200 US Std Sieve and 30-50% thru a 200 US Std Sieve) 88% and Gulf Crown Oil E or Gulf 300 Process Oil [(95%) + Lecithin (5%)1 12%. Its properties resembled the British PE No 2, but possessed improved low temperature behavior... 

After a series of accidents in the US, mainly in loading plants and depots, a more insensitive Torpex containing a greater quantity of wax was developed. The British formulation (Ref 30) for the wax desensitizer for Torpex consisted of 84/14/2 paraffm/low density nitrocellulose (12.2% nitrogen)/lecithin. The US version of this material (Ref 32), known as Compn D-l, has the following formulation (see Vol 3, C488) ... 

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). 

Film penetration studies show unequivocally that lecithin-cholesterol mixtures containing from 0 to 50 mole % cholesterol and lecithin—lactoside mixtures containing from 0 to 80 mole % Ci6-dihydroceramide lactoside have the same effect as pure lecithin. This suggests the presence of a lipid complex in which lecithin prevents the interaction of the cholesterol or ceramide lactoside with globulin. Over these ranges of composition the lipid film would consist of a mixture of the lecithin-cholesterol or the lecithin-lactoside complex with excess lecithin. One may picture two models in which the protein contact is restricted to molecules of lecithin. In one, individual polar groups of the protein interact with the excess lecithin molecules as well as with the lecithin portions of the complex. In the other model, the protein as a whole interacts with the lecithin sites of polymeric lipid structures. The latter, which could be referred to as surface micelles (I), are visualized also through the term "mono-... 

A model that is consistent with these observations of the action of trypsin and phospholipase A and with the discontinuities in the All-composition curves (Figures 2 and 3) is one in which the lipid monolayer is not a continuous palisade of uniformly oriented lipid molecules but rather an assembly of surface micelles. In this model, proposed by Colacicco (4, 5), the protein first comes into contact with the lipid molecules at the periphery of the surface micelles and then inserts itself as a unit between them. This is the basis for the generalized nonspecific interaction between lipids and proteins which results in increase of surface pressure. One may thus explain the identical All values obtained with films of lecithin and 80 mole % lactoside by picturing the lecithin molecules outside and the lactoside molecules inside the surface micelles. In this model lecithin prevents the bound lactoside from interacting nonspecifically with globulin and produces the same increase in pressure as with a film of pure lecithin. In the mixed micelle the lactose moiety of the lactoside protrudes into the aqueous subphase. Contact of the protein with these or other nonperipheral regions of the surface micelle would not increase the surface pressure. 

The nature of the lecithin-cholesterol association is probably also that of a complex (1 to 1), in which the OH group of cholesterol is involved through hydrogen bonding. It is not known, however, whether the monolayer consists of a uniform population of bimolecular complexes or of configurations (surface micelles) in which cholesterol molecules are surrounded by an equal number of lecithin molecules. 

Bile consists of a watery mixture of organic and inorganic compounds. Phosphatidylcholine (lecithin, see p. 201) and bile salts (conjugated bile acids) are quantitatively the most important organic components of bile. Bile can either pass directly from the liver where it is synthesized into the duodenum through the common bile duct, or be stored in Ihe gallbladder when not immediately needed for digestion. 

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