Surfactant emulsifier lecithin

Low-molecular-weight surfactants ( emulsifiers ) are important ingredients in food products. The types of surfactants most commonly studied in food colloids research are phospholipids (lecithin), mono/diglycerides (particularly glycerol monostearate), polysorbates (Tweens), sorbitan monostearate or monooleate (Spans), and sucrose esters. These small lipid-based amphiphiles can typically lower the interfacial tension to a greater extent than the macromolecular amphiphiles such as proteins and certain gums (Bos and van Vliet, 2001). 

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 range of surfactant emulsifiers used in pharmaceutical preparations is illustrated in Table 2. Surfactants are manufactured from a variety of natural and synthetic sources and consequently they show considerable batch-to-batch variations in their homologue compositions and in trace impurities from the starting material. For example, batch variations in the number of neutral phospholipids occur in lecithin surfactants and non-ionic polyethylene surfactants show variations in the number of moles of ethylene oxide. The mechanisms by which such batch variations lead to differences in emulsifying properties are now better understood. Although synthetic and semisynthetic surfactants form by far the largest group of emulsifiers studied in the scientific literature and many of them are available commercially, their use in pharmaceutical emulsions is limited by the fact that the majority are toxic (i.e., haemolytic) and irritant to the skin and mucous... 

Mono-diglyceride mixtures as well as distilled monoglycerides are extensively used in many industrially produced foods and often in combination with other surfactants or lecithin. Historically the first monoglycerides were applied five decades ago in the production of margarine and monoglycerides are still the emulsifier chosen to facilitate the emulsification of the water phase in the oil and fat phase of margarine. Low-calorie spreads could not be produced without surfactants such as monoglycerides. 

Natural surfactants like lecithin are of special interest for food and pharmaceutical industry. However properties of gelatin/lecithin mixtures are practically not described in current publications. Combinations of gelatin with lecithin as emulsifiers and stabilizers of traditional and new food recipes can provide new perspective products, and that is why studies of these systems are of actual importance. The interrelation between the rheological properties of interfacial absorption layers containing proteins and low-molecular-weight surfactants [14-21] and the behavior of emulsions (including its stability) is also of significant values. 

Animal Feed. In animal feeds (1—3% lecithin) lecithin is an emulsifier wetting and dispersiag agent energy source antioxidant surfactant source of choline, organically combiaed phosphoms and iaositol and Hpotropic agent. It is used ia a milk replacer formula for calves (approximately 10,000 t of lecithin ate used for this purpose) and for veal production, ia mineral feeds, poultry feeds, fish foods, pet foods, and feeds for fur-beating animals (30). 

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. 

Emulsifiers. The chemical structures of emulsifiers, or surfactants, enable these materials to reduce the surface tension at the interface of two immiscible surfaces, thus allowing the surfaces to mix and form an emulsion. An emulsifier consists of a polar group, which is attracted to aqueous substances, and a hydrocarbon chain, which is attracted to lipids. Emulsifiers include mono- and diglycerides, lecithin, propylene glycol esters, luctylated esters, sorbttan and sorbitol esters, polysorbate.x, and sucrose esters. 

The use of surfactants in the food industry has been known for centuries. Naturally occurring surfactants such as lecithin from egg yolk or soybean and various proteins from milk are used for the preparation of many food products, such as mayonnaise, salad creams, dressing, and desserts. Polar lipids such as monoglycerides have been introduced as emulsifiers for food products. More recently, synthetic surfactants such as sorbitan esters (Spans) and their ethoxylates (Tweens), sucrose esters, have been used in food emulsions. It should be mentioned that the structures of many food emulsions is complex, and in... 

The hydrophilicity of nonionic surfactants can be characterized numerically as their hydrophile-lipophile balance (HLB). An HLB value of 3-6 indicates that the compound is a likely W/O emulsifier 7-9, a wetting agent 8-13, an O/W emulsifier 13-15, a detergent and 15-18, a solubilizer (of oil or other nonpolar compounds) in water. The HLB values of some common compounds are presented in Table 34.12.170 An HLB value of 8.0 is shown in Table 34.12 for lecithin, but manufacturers are able to supply modified lecithins with values of2-12. 

Solubilization. Most lecithins can aid in the production of microemulsions, an example being oil-soluble flavors in aqueous systems. Although standard-grade lecithins do not disperse in water, many modified or fractionated lecithins are water-dispersible, and they can be used to produce microemulsions. Standard-grade lecithin can be blended with other surfactants (e.g., ethoxylated monoglycerides) to produce synergistic emulsifier blends that are also effective in producing microemulsions. 

As mentioned previously, soybean lecithin is used in food because of its emulsifying, wetting, release, and other surfactant qualities. Relatively small amounts of the lecithin are needed, often only 0.1% to 2% in foods. These use levels are more or less consistent with those of chemical surfactants (7). At these low levels of usage, the color, flavor, and odor of the lecithin normally are not noticeable. When lecithin is used in conjunction with synthetic emulsifiers, it sometimes has a synergistic effect, and thus lesser amounts of the synthetic emulsifiers need be used. 

Typical solid lipids used are glycerides and/or fatty acids, and may constitute 30% of the formulation. These are from the same family of lipids found in parenteral nutrition emulsions, such as Intralipid, which have been successfully administered intravenously for several decades. Typical excipients are Dynasan 112, composed of short chain fatty acids, Compritol, lecithin, used as an emulsifier, and surfactants such as polysorbate 80, polaxamer 188, PVP, bile salts such as sodium glycocholate, and Span 85. Water can be replaced with oils or PEG 600 to yield dispersions which can be filled into soft gelatin capsules. 

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