Emulsions formation

Generally, chunks are produced by forming emulsions of meats and binders through the application of heat and pressure. Binders that are generally used in pet food production include starches, carrageenan, WG, egg albumen, konjac powder, etc. A more heat-stable binder can be applied in a formula to reduce syneresis, which is the separation of water from a product after retorting (Shi and Tang, 2003). 

Ingredients and heating condition are important factors influencing the flavor of moist pet foods. The main ingredient affecting the flavor of moist pet foods is fat, because crude fat acts as an oil-soluble flavor carrier. Bacon and chicken fats, for example, have strong aroma characteristics and tastes (Hanna, 1976). The fat flavor is influenced by relative protein tissues and the nature of the fat itself. A suitable amount of fats in moist pet foods is around 3%-6% of a final product. Excess fats in moist pet foods may lead to a problem of nutrition balance and inversely affect the 

FIGURE 11.5 Relationship between hardness of cooked chnnk and ponltry fat content, and use of SDAP and WG. (Modified from Polo, J. et al., Anim. Feed Sci. TechnoL, 133, 309, 2007.) 

Low moisture content also has a negative effect on the palatability of moist pet foods. Several producers thus try to increase the moisture content of the products 

The preparation of an emulsion requires the formation of a very large amount of interfacial area between two immiscible liquids. If a sample of 10 mL of an oil is emulsified in water to give a droplet diameter of 0.2 / m, the resulting o/w interfacial area will have been increased by a factor of approximately 10 . The work required to generate one square centimeter of new interface is given by 

Department of Food Science, Wageningen Agricultural University, PO Box 8129, 6700 EV Wageningen, The Netherlands 

To make an emulsion, oil, water, surfactant and energy are needed. The composition of the system and the way of processing then determine emulsion type (oil-inwater or water-in-oil), droplet volume fraction ( ), droplet size and composition of the layer of surfactant around the droplets. These variables determine most emulsion properties, notably physical stability. Consequently, knowledge of emulsion formation is of considerable importance. In this chapter, a review is given, with some emphasis on newer developments. Some aspects are left out, because they have been sufficiently discussed in earlier reviews. For the convenience of the reader, however, important general points are recalled. Some aspects are not discussed, such as the preparation of high-internal phase emulsions, double emulsions, microemulsions and emulsions with very coarse drops. Typically, the emulsions considered have droplets of, say, a micrometre in diameter. Some specialized methods of emulsion formation will also be left out. 

Making drops is easy, and it will not be discussed here see an earlier review. In many cases, however, small drops are desired, and making these is difficult or, in other words, it costs a large amount of energy and/or surfactant. This is because of the drop s Laplace pressure p, defined as the difference between the pressure inside and outside the droplet, which is given by 

In the following, results on droplet size distribution will often be given. If the number frequency of droplets as a function of droplet diameter d is given by f( /), the nth moment of the distribution then is 

In most cases, d (the volume/surface average or Sauter mean), or d i will be used. 

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The cleaning process proceeds by one of three primary mechanisms solubilization, emulsification, and roll-up [229]. In solubilization the oily phase partitions into surfactant micelles that desorb from the solid surface and diffuse into the bulk. As mentioned above, there is a body of theoretical work on solubilization [146, 147] and numerous experimental studies by a variety of spectroscopic techniques [143-145,230]. Emulsification involves the formation and removal of an emulsion at the oil-water interface the removal step may involve hydrodynamic as well as surface chemical forces. Emulsion formation is covered in Chapter XIV. In roll-up the surfactant reduces the contact angle of the liquid soil or the surface free energy of a solid particle aiding its detachment and subsequent removal by hydrodynamic forces. Adam and Stevenson s beautiful photographs illustrate roll-up of lanoline on wood fibers [231]. In order to achieve roll-up, one requires the surface free energies for soil detachment illustrated in Fig. XIII-14 to obey... 

Occasionally emulsions are formed in the extraction of aqueous solution by organic solvents, thus rendering a clean separation impossible. Emulsion formation is particularly liable to occur when the aqueous... 

Mix 31 g. (29-5 ml.) of benzyl alcohol (Section IV, 123 and Section IV,200) and 45 g. (43 ml.) of glacial acetic acid in a 500 ml. round-bottomed flask introduce 1 ml. of concentrated sulphuric acid and a few fragments of porous pot. Attach a reflux condenser to the flask and boil the mixture gently for 9 hours. Pour the reaction mixture into about 200 ml. of water contained in a separatory funnel, add 10 ml. of carbon tetrachloride (to eliminate emulsion formation owing to the slight difference in density of the ester and water, compare Methyl Benzoate, Section IV,176) and shake. Separate the lower layer (solution of benzyl acetate in carbon tetrachloride) and discard the upper aqueous layer. Return the lower layer to the funnel, and wash it successively with water, concentrated sodium bicarbonate solution (until effervescence ceases) and water. Dry over 5 g. of anhydrous magnesium sulphate, and distil under normal pressure (Fig. II, 13, 2) with the aid of an air bath (Fig. II, 5, 3). Collect the benzyl acetate a (colourless liquid) at 213-215°. The yield is 16 g. 

The Karr column is particularly well suited for systems which tend to emulsify since its uniform shear characteristics tend to minimize emulsion formation. It is also particularly well suited for corrosive systems (since the plates can be constructed of non-metals) or for systems containing significant solids (due to its large open area and hole size on the plates). Slurries containing up to 30 percent solids have been successfully processed in Karr columns. 

Emulsions Almost eveiy shear rate parameter affects liquid-liquid emulsion formation. Some of the efrecds are dependent upon whether the emulsion is both dispersing and coalescing in the tank, or whether there are sufficient stabilizers present to maintain the smallest droplet size produced for long periods of time. Blend time and the standard deviation of circulation times affect the length of time it takes for a particle to be exposed to the various levels of shear work and thus the time it takes to achieve the ultimate small paiTicle size desired. 

If less than 600-cc. portions of benzene are used, the danger of emulsion formation is greater. 

Clear Brines. Brine solutions are made from formation saltwater, seawater, or bay water, as well as from prepared saltwater. They do not contain viscosifers or weighting materials. Formation water-base fluids should be treated for emulsion formation and for wettability problems. They should be checked on location to ensure that they do not form a stable emulsion with the reservoir... 

The multiple emulsion technique includes three steps 1) preparation of a primary oil-in-water emulsion in which the oil dispersed phase is constituted of CH2CI2 and the aqueous continuous phase is a mixture of 2% v/v acetic acid solution methanol (4/1, v/v) containing chitosan (1.6%) and Tween (1.6, w/v) 2) multiple emulsion formation with mineral oil (oily outer phase) containing Span 20 (2%, w/v) 3) evaporation of aqueous solvents under reduced pressure. Details can be found in various publications [208,209]. Chemical cross-linking is an option of this method enzymatic cross-linking can also be performed [210]. Physical cross-linking may take place to a certain extent if chitosan is exposed to high temperature. 

Compositions of a N,N-dialkylamide of a fatty acid in a hydrocarbon solvent and a mutual oil-water solvent are useful for the prevention of sludge formation or emulsion formation during the drilling or workover of producing oil wells [1526,1528,1529]. 

M. Fingas. Water-in-oil emulsion formation A review of physics and mathematical modelling. Spill Sci Technol Bull, 2(l) 55-59, March 1995. 

H.-Y. Lee, M. J. McCarthy, S. R. Dungan 1998, (Experimental characterization of emulsion formation and coalescence by nuclear magnetic resonance restricted diffusion techniques), J. Am. Oil Chem. Soc. 75, 463. 

In-situ emulsion formation, as proposed by Kamath et al(19), with DAS surfactants may cause higher pressure drops across the core. This is because of the blocking tendency of the emulsion which has lower mobility. This could explain the earlier plugging of the core compared to other runs. Effluent pH and viscosity showed behavior similar to the previous runs. It is worthwhile noting here that such pressure drops were not manifested by face plugging of the core near the entrance. This was confirmed by simultaneously monitoring the pressure at the inlet end of the core as well as the differential pressure across the two pressure taps located about 1 cm. from each end of the core. The inlet end pressure transducer showed reasonably low pressures throughout the run for each experiment. 

Izquierdo, P., Feng, J., Esquena, J.,Tadros, T.F., Dederen, J.C., Garcia, M.J., Azemar, N. and Solans, C. (2005) The influence of surfactant mixing ratio on nano-emulsion formation by the PIT method. Journal of Colloid and Interface Science, 285 (1), 388-394. 

Fernandez, P., Andre, V., Rieger, J. and Kuhnle, A. (2004) Nano-emulsion formation by emulsion phase inversion. Colloids and Surfaces A Physicochemical and Engineering Aspects, 251, 53-58. 

Ester addition must be quite slow (2 drops per second or less) to prevent emulsion formation and extremely low yields. 

The Kies extraction apparatus4 is useful in minimizing emulsion formation. The checkers performed the countercurrent extractions successfully in separatory funnels. The solutions must be mixed by mild rocking of the funnels otherwise serious emulsions will be produced. 

Application of SPE to sample clean-up started in 1977 with the introduction of disposable cartridges packed with silica-based bonded phase sorbents. The solid phase extraction term was devised in 1982. The most commonly cited advantages of SPE over liquid-liquid extraction (LLE) as practiced on a macroscale include the reduced time and labor requirements, use of much lower volumes of solvents, minimal risk of emulsion formation, selectivity achievable when desired, wide choices of sorbents, and amenability to automation. The principle of operation consists of four steps (1) conditioning of the sorbent with a solvent and water or buffer, (2) loading of the sample in an aqueous or aqueous low organic medium, (3) washing away unwanted components with a suitable combination of solvents, and (4) elution of the desired compound with an appropriate organic solvent. 

The effective and meaningful extraction of an analyte is rendered almost impossible when one encounters an emulsion formation during an extraction process thereby the separation of the two phases becomes difficult. Actually, it offers a frequent and serious problem when dealing with the extraction of drugs from biological as well as pharmaceutical formulations. 

Emulsion formation enhances the area of the interface between the two immiscible solvents and as a result also enhances the free energy of the system, which may be designated by the following expression ... 

There are precautions that must be taken when attempting to separate heavy feedstocks or polar feedstocks into constituent fractions. The disadvantages in using ill-defined adsorbents are that adsorbent performance differs with the same feed and in certain instances may even cause chemical and physical modification of the feed constituents. The use of a chemical reactant such as sulfuric acid should only be advocated with caution since feeds react differently and may even cause irreversible chemical changes and/or emulsion formation. These advantages may be of little consequence when it is not, for various reasons, the intention to recover the various product fractions in toto or in the original state, but in terms of the compositional evaluation of different feedstocks, the disadvantages are very real. 

Petroleum is typically described in terms of its physical properties (such as density and pour point) and chemical composition (such as percent composition of various petroleum hydrocarbons, asphaltenes, and sulfur). Although very complex in makeup, crude can be broken down into four basic classes of petroleum hydrocarbons. Each class is distinguished on the basis of molecular composition. In addition, properties important for characterizing the behavior of petroleum and petroleum products when spilled into waterways or onto land and/or released into the air include flash point, density (read specific gravity and/or API gravity), viscosity, emulsion formation in waterways, and adhesion to soil. 

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