Emulsifiers natural substances

An emulsion is a dispersed system of two immiscible phases. Emulsions are present in several food systems. In general, the disperse phase in an emulsion is normally in globules 0.1-10 microns in diameter. Emulsions are commonly classed as either oil in water (O/W) or water in oil (W/O). In sugar confectionery, O/W emulsions are most usually encountered, or perhaps more accurately, oil in sugar syrup. One of the most important properties of an emulsion is its stability, normally referred to as its emulsion stability. Emulsions normally break by one of three processes creaming (or sedimentation), flocculation or droplet coalescence. Creaming and sedimentation originate in density differences between the two phases. Emulsions often break by a mixture of the processes. The time it takes for an emulsion to break can vary from seconds to years. Emulsions are not normally inherently stable since they are not a thermodynamic state of matter. A stable emulsion normally needs some material to make the emulsion stable. Food law complicates this issue since various substances are listed as emulsifiers and stabilisers. Unfortunately, some natural substances that are extremely effective as emulsifiers in practice are not emulsifiers in law. An examination of those materials that do stabilise emulsions allows them to be classified as follows ... 

Emulsions are not normally inherently stable since they are not a thermodynamic state of matter - a stable emulsion normally needs some material to give it its stability. Food law complicates this issue since various substances are listed as emulsifiers and stabilisers. Unfortunately, some natural substances that are extremely effective as emulsifiers in practice are not emulsifiers in law. An examination of those materials that do stabilise emulsions allows them to be classified as follows ... 

Emulsifiers, naturally, tend to attract the attention of food legislators, and it is entirely reasonable that only those substances that are safe for food use are permitted. The thing that is difficult to understand is why the permitted emulsifiers vary so much between countries. The EU is, however, working towards rationalisation in this area. 

Emulsions are commonly prepared by mixing the oil (o) and water (w) in the presence of one or more emulsifiers, under vigorous agitation. Emulsifiers are substances that adsorb strongly at the oil-water Interface. We shall assume that there is only one, and call it the surfactant. The type of emulsion that is formed depends primarily on the nature of the surfactant. According to the empirical Bancroft rule this type tends to be such that the phase into which the surfactant is more soluble becomes the continuous one. So, hydrophilic surfactants promote the formation of oil-water emulsions, for hydrophobic surfactants it is the other way around. A host of commercial emulsifiers are available, tailor-made for certain purposes, but the above rule remains generally valid. 

Emulsifiers are derived from natural substances. Emulsifiers are available and are used as semi-purified preparations of natural products or are available as products of synthesis or reaction of natural substances. Table 3.36 indicates a range of common food emulsifiers together with an outline of their origin. 

There are a large number of emulsifiers of natural and synthetic origin, which fit into the surfactant classification given. The natural substances used as emulsifiers all fit into this system (See Table 4). 

When the primary target is oil removal, we should distinguish between the forms of oil. There are two forms of oil that we find in wastewater. Free oil is oil that will separate naturally and float to the surface. Emulsified oil is oil that is held in suspension by a chemical substance (Detergents - Surfactants) or electrical energy. When making an evaluation, free oil will normally separate by gravity and float to the surface in approximately 30 minutes. Emulsified oil is held in a molecular... 

Micelles are approximately spherical aggregates of surfactant molecules with their nonpolar tails in the interior and their hydrophilic ends oriented towards the aqueous medium. They are some 50-100 A in diameter. The bulk concentration of surfactant is usually around 0.1 M and this corresponds to approximately I o micelles per milliliter of aqueous phase, since there are typically about 50-100 emulsifier molecules per micelle. The apparent water solubility of organic molecules is enhanced by micellar surfactants, because the organic molecules are absorbed into the micelle interiors. The extent of this solubilization of organic molecules depends on the surfactant type and concentration, the nature of the solubilized organic substance, and the concentration of electrolytes in the aqueous phase. As an example, there will be about an equal number of styrene molecules and potassium hexadecanoate (palmitate) molecules in a micelle of the latter material. In this case about half the volume of the micelle interior is occupied by solubilized monomer, and the concentration of styrene is approximately 4.5 M at this site. Thus radical polymerization starts very rapidly in the interior of a micelle once it is initiated there. 

Another parameter that influences the overall properties of the bulk emulsion is the physical state of the lipid droplets in an emulsion (17, 19, 28-31). Crystallization of lipid droplets in emulsions can be either beneficial or detrimental to product quality. Margarine and butter, the most common water-in-oil emulsions in the food industry, are prepared by a controlled destabilization of oil-in-water emulsions containing partly crystalline droplets. The stability of dairy cream to mechanical agitation and temperature cycling depends on the nature and extent of crystallization in milk-fat globules. It should be noted that because the density of the phases can change as crystallization occurs, the rate at which milkfat droplets cream can be altered as droplets solidify. Emulsion manufacturers should therefore understand which factors influence the crystallization and melting of emulsified substances, and be aware of the effect that droplet phase transitions can have on the properties of emulsions. 

When surface active agents are considered, a further complication may be encountered. Because of their surface active nature, the surfactants not only emich at the surfaces, but also form extended structures themselves. At low concentrations, the surfactants remain as dissolved monomers or asssociate to oligomers. However, when the critical micellization concentration (cmc) is surpassed, a cooperative association is activated to micelles (1 to 10 nm) consisting typically of some 50 to 100 monomers. At stiU higher concentrations, or in the presence of cosurfactants (alcohols, amines, fatty acids, etc.), liquid crystalline phases may separate. These phases have an infinite order on the x-ray scale, but may remain as powders on the NMR (nuclear magnetic resonance) scale. When the lamellar liquid crystalline phase is in equilibrium with the liquid micellar phase the conditions are optimal for emulsions to form. The interface of the emulsion droplets (1 to 100 pm) are stabilized by the lamellar liquid crystal. Both the micelles and the emulsions may be of the oil in water (o/w) or water in oil (w/o) type. Obviously, substances that otherwise are insoluble in the dispersion medium may be solubilized in the micelles or emulsified in the emulsions. For a more thorough analysis, the reader is directed to pertinent references in the literature. ... 

Stabilization of emulsions by powders can be viewed as a simple example of structural- mechanical barrier, which is a strong factor of stabilization of colloid dispersions (see Chapter VIII, 5). The stabilization of relatively large droplets by microemulsions, which can be formed upon the transfer of surfactant molecules through the interface with low a (Fig. VII-10), is a phenomenon of similar nature. The surfactant adsorption layers, especially those of surface active polymers, are also capable of generating strong structural mechanical barrier at interfaces in emulsions. Many natural polymers, such as gelatin, proteins, saccharides and their derivatives, are all effective emulsifiers for direct emulsions. It was shown by Izmailova et al [49-52]. that the gel-alike structured layer that is formed by these substances at the surface of droplets may completely prevent coalescence of emulsion drops. 

It is well known that dietary fat is not absorbed from the intestine unless it has been subjected to the action of pancreatic lipase [1], Previously, we found that basic proteins such as protamines, histones and purothionine inhibited the hydrolysis of triolein emulsified with phosphatidylcholine [2], The inhibition of hydrolysis of dietary fat may cause a decrease or delay in the intestinal absorption of fat and reduce blood chylomicron levels, an excess of which is known to induce obesity [3], Therefore, there was a possibility that inhibitory substances toward pancreatic lipase activity may prevent the onset of obesity induced by feeding a high fat diet to mice. Recently, we found that natural products such as tea saponin, platycodi radix saponin, chitin-chitosan and chondroitin sulfate inhibited the pancreatic lipase activity. In the following section, the anti-obesity effects of these natural products will be described in detail. 

Pemcreatin.—Under this name, substances obtained from the pancreatic secretion, and from extracts of the organ itself, have been described, and to some extent used therapeutically. They do not, however, contain all the cryptolytes of the pancreatic juice, and in many instances are inert albuminoids. The actions of the pancreatic juice are (1) it rapidly converts starch, raw or hydrated, into sugar (2) in alkaline solution—its natural reaction —it converts albuminoids into peptone (3) it emulsifies neutral fats (4) it decomposes fats, with absorption of HjO and liberation of glycerin and fatty acids. 

Stabilizers is a very general term that includes inhibitors, antioxidants, and emulsifiers which keep or retard a substance from changing its chemical form or nature. For example, acetone cyanohydrin readily decomposes to hydrocyanic acid and acetone unless it is stabilized. Unstabilized substances are those that might otherwise have had a stabilizer added or which have had the stabilizer removed. See Terminology, Inhibited, p.241. 

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