Emulsifier hydrophilic-lipophilic balance value

The manner in which lecithin is modified to achieve increased hydrophilicity will greatly affect its emulsification properties. Different modifications will create lecithin products with different apparent HLB (hydrophile-lipophile balance) values, a term used to convey the approximate degree of water dispersibility (hydrophilicity) of lecithin products (31). The higher its HLB value, the more water dispersible the lecithin product. In o/w emulsions, the type of fat to be emulsified may require a specific type of hydrophilic lecithin for optimum emulsion stability. Dashiell (31) provides a short listing of fat types, and the corresponding class of lecithin found to give the most stable emulsion in model systems of water/fat/ emulsifier. 

The number of different emulsifiers is in the thousands. Even restricting selection to nonylphenol ethoxylates leaves many choices. Some parameter is necessary to compare emulsifiers. Hydrophilic/Lipophilic balance (HLB number) was developed by W.C. Griffin (Griffin, 1949, 1954) in the 40 s and describes emulsifying properties of a surfactant. Values vary between 0 and 20. A low HLB, such as 4, indicates an oil soluble emulsifier useful for dissolving small amounts of water into oil. A large number, such as 16, indicates a water soluble emulsifier useful for dissolving small amounts of oil into water. The HLB number can be determined experimentally or calculated for alkyl and aryl ethoxylates from Equation 1. 

Greth and Wilson [100] successfully applied, in the emulsion polymerization of unsaturated monomers, a method of classifying emulsifiers based on the HLB (hydrophilic/lipophilic balance) value. They plotted the most important properties of the emulsion polymerization system, i.e., the latex stability, particle size, emulsion viscosity, and rate of polymerization against the HLB value of emulsifiers used. The dependence is described by a curve with maximum or minimum at a certain value of HLB, as it is expected from the micellar model [6, 7]. 

Emulsifiers are classified by the hydrophilic—lipophilic balance (HLB) system. This system indicates whether an emulsifier is more soluble in water or oil, and for which type of emulsion (water-in-oil or oil-in-water) it is best suited. Emulsifiers having alow HLB value are more oil soluble, and are better suited for water-in-oil appHcations such as margarine. Conversely, emulsifiers having a high HLB value are more water soluble, and function more effectively in oil-in-water emulsions such as ice cream (34). The use of this system is somewhat limited because the properties of emulsifiers are modified by the presence of other ingredients and different combinations of emulsifiers are needed to achieve a desired effect. The HLB values of some common emulsifiers are given (35). 

One of the most important characteristics of the emulsifier is its CMC, which is defined as the critical concentration value below which no micelle formation occurs. The critical micelle concentration of an emulsifier is determined by the structure and the number of hydrophilic and hydrophobic groups included in the emulsifier molecule. The hydrophile-lipophile balance (HLB) number is a good criterion for the selection of proper emulsifier. The HLB scale was developed by W. C. Griffin [46,47]. Based on his approach, the HLB number of an emulsifier can be calculated by dividing... 

Formation of emulsions of the oil-in-water or water-in-oil type depends mainly on the hydrophilic-lipophilic balance (HLB) of the emulsifier. Phosphate esters with their various molecular structures can be adjusted to nearly every HLB value desired. Therefore they are able to meet nearly all of demands in this field. 

The amphiphilic nature of many emulsifying agents (particularly non-ionic surfactants) can be expressed in terms of an empirical scale of so-called HLB (hydrophile-lipophile balance) numbers222 (see Table 10.1). The least hydrophilic surfactants are assigned the lowest HLB values. Several formulae have been established for calculating HLB numbers from composition data and they can also be determined experimentally - e.g. from cloud-point measurements123,125. For mixed emulsifiers, approximate algebraic additivity holds. 

The hydrophile-lipophile balance (HLB) system is the measure of the surfactant s polarity as well as other physical properties of surfactants and the emulsifying materials. The more lipophilic the surfactant is, the lower the HLB values will be. Table 4.5 empirically classifies and compares surfactants according to their optimum use. Table 4.6 shows the HLB values for a selected group of surfactants. The HLB value of the surfactant or surfactant mixture should be matched with that of the oil or the mixture of oils to ensure a stable emulsion. The required HLB values of a... 

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. 

Griffin devised the concept of hydrophile-lipophile balance (HLB) and its additivity many years ago for selection of non-ionic emulsifiers and this rather empirical method is still widely used. The enormous literature on the HLB of surfactants has been reviewed by Becher. Each surfactant is allocated an HLB number usually on a scale of 0-20, based on the relative proportions of the hydrophilic and hydrophobic part of a molecule. Water-in-oil emulsions are formed generally from oil-soluble surfactants of low HLB number and oil-in-water emulsions from more hydrophilic surfactants of high HLB number. The method of selection is based on the observation that each type of oil will require an emulsifying agent of a specific HLB number to produce a stable emulsion. Thus, oils are often designated two required HLB numbers, one low and one high, for their emulsification to form water-in-oil and oil-in-water emulsions respectively. A series of emulsifiers and their blends with HLB values close to the required HLB of the oil are then examined to see which one forms the most stable emulsion (c.f. Fig. lA). 

The most widely used system for classifying emulsifiers is the hydrophile-lipophile balance (HLB) concept (Griffin (1949)/77)- A low HLB number means that the emulsifier is lipophilic and a high value means that it is hydrophilic. 

Figure 21.1 points out the key parameters which determine the nature of the dispersion [3]. These are the emulsifier concentration (horizontal axis) and the hydrophile-lipophile balance (HLB) of the emulsifier (vertical axis). According to Bancroft s rule, HLB values higher than 7 favour the formation of oil-in-watCT... 

The w/o/w or o/w/o emulsions are important, in particular when the protection of sensitive ingredients or controlled release of active substances is required [54]. Silicone-based emulsifiers are suited for these applications. They are strongly adsorbed at the oil interface, and do not migrate from one interface to the other, thus preventing the destabilization. Two emulsifiers have to be used to stabilize these multiphase emulsions. The hydrophilic-lipophilic balance (HLB) values of the emulsifiers should be above 10 for the hydrophilic emulsifier and below 6 for the hydrophobic emulsifier [54]. 

Bancroft summarized the results of emulsification experiments carried out from the late I9th until the early 20th century by a rule of thumb which stated that in order to have a kinetically stable emulsion the emulsifying agent must be soluble in the continuous phase (23). In principle, this rule finds its expression in the empirical system of the HLB values (hydrophilic-lipophilic balance) which was developed in the middle of the 20th century to allow the... 

An empirical scale developed for categorizing single-component or mixed (usually nonionic) surfactants is the hydrophile-lipophile balance or HLB scale. This dimensionless scale ranges from 0 to 20 for nonionic surfactants a low HLB (<9) refers to a lipophilic surfactant (oil soluble) and a high HLB (>11) to a hydrophilic (water soluble) surfactant. Most ionic surfactants have HLB values greater than 20. Some examples of surfactant HLB s are given in Table 6. In general, W/O emulsifiers exhibit... 

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