Lecithin added emulsifiers

Emulsifiers are added to toffees to help disperse the fat (see also Chapter 4), although it is perfectly possible to make toffees that do not contain added emulsifiers if sufficient skim milk solids are present. The emulsifying effect of a considerable quantity of skim milk solids can be replaced by a very small quantity of an emulsifier, e.g. lecithin or distilled monoglycerides, and the price of skim milk in the EU makes this an attractive proposition. Curiously, fat that is too well dispersed can cause problems. If some fat coats the surface of the piece then the toffee will cut easily as the fat lubricates the cutting knife if there is no surface fat then the toffee can stick to the knife. One solution to this is to have a cutting knife coated with PTFE. The PTFE has a very low energy surface that the toffee will not stick to. 

Lecithin is added to foods such as mayonnaise as an emulsifying agent to prevent the fat and water from sepa rating into two layers... 

Mean particle size ranges 50 to 1000 mn. Depending on the type and concentration of the lipid, 0.5 to 5% emulsifier (surfactant) has to be added for physical stabilization. For dermal use, surfactants are very often poloxamer 188, polysorbate 80, lecithin, tyloxapol, polyglycerol methylglucose distearate (Tegocare 450), sodinm cocoamphoacetate (Miranol Ultra C32), or saccharose fatty acid ester. 

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,... 

The phosphoric acid esters of diacyl glycerides, phospholipids, are important constituents of cellular membranes. Lecithins (phosphatidyl cholines) from egg white or soybeans are often added to foods as emulsifying agents or to modify flow characteristics and viscosity. Phospholipids have very low vapor pressures and decompose at elevated temperatures. The strategy for analysis involves preliminary isolation of the class, for example by TLC, followed by enzymatic hydrolysis, derivatization of the hydrolysis products, and then GC of the volatile derivatives. A number of phospholipases are known which are highly specific for particular positions on phospholipids. Phospholipase A2, usually isolated from snake venom, selectively hydrolyzes the 2-acyl ester linkage. The positions of attack for phospholipases A, C, and D are summarized on Figure 9.7 (24). Appropriate use of phospholipases followed by GC can thus be used to determine the composition of phospholipids. 

Lecithin is another food constituent which has been shown to cause neurobehavioral teratogenic effects in rats. It is added to foods as an emulsifier, but it is also present in soy lecithin preparations which are consumed as healthy food supplements. Soy lecithin preparations contain various phospholipids which can be incorporated into the brain as membrane constituents or acetylcholine, and conceivably may affect brain development if available in high levels. Pregnant dams were fed a lecithin-enriched diet (prepared by adding a commercial soy lecithin preparation) from gestational day 7 until weaning. Subsequently, the pups were also fed this diet. Treated pups showed faster rightening responses on postnatal days 1 and 2 and slower... 

Milk replacer fat emulsion. One important application of lecithin in animal feeds is as an emulsifier (314). As an example, milk replacer fat is emulsified to improve product wetting and dispersion upon mixing, to help minimize fat separation (i.e., emulsion stability), and to significantly reduce fat particle size, allowing improved fat digestibility. As an emulsifier in milk replacers, lecithin is used at 3-12% of the added fat. The type of lecithin used is affected by factors such as fat type, protein type, and the presence of stabilizers. 

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. 

When the emulsion is made the pre-heated condensed milk, fat and emulsifying agent (lecithin) are added to the hot sugar solution. A relatively stable water-fat emulsion can be produced by intensive mixing. 

The fine ground chocolate powder or paste is conveyed into refining equipment where the rest of the cocoa butter, emulsifying agent (lecithin) and the flavourings are added. 

Figure 10 (Left) The rates of hydrolysis of emulsified long-chain triglycerides by pancreatic lipase. The highest rate occurs with triglycerides emulsified with gum arabic (no lecithin). All the other curves represent hydrolysis rates of triglycerides emulsified with long-chain lecithin. There is a long lag period and then a slight hydrolysis in the absence of additives. With added bile salts, the lag period is abolished, but the hydrolysis rates ate still low. Both colipase and colipase plus bile salts accelerate the hydrolytic rates. (Right) Concerted action of pancreatic lipase and phospholipase. Addition of phospholipase A2 hydrolyzes the phospholipid emulsifier (as indicated by the lysolecithin release), stops the lag phase, and initiates an accelerated triglyceride hydrolysis. (From Ref. 35.)...

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