Emulsion texture viscosity

Thickeners are applied in order to increase the viscosity of the continuous phase of the emulsion. Thus, the droplet movement is decreased, resulting in a reduced coalescence rate and sedimentation. At the same time the emulsion texture is changed. 

Soy Protein Concentrates. Both non-functional (low or no solubility) and functional (good solubility, emulsification capacity, and dispersibility) soy protein concentrates (70% protein, dry basis) are commercially available for use in meat products (2-4, 6, j), 15) Normally, a highly functional product with no harsh or bitter flavors is desirable. When used to replace lean meat, non-hydrated concentrate can be used at levels up to 6-7% in finished nonspecific emulsion meats Higher replacement levels or formulas with specific cost/nutrition requirements may use soy protein concentrate with a judicious amount of textured soy protein (6). Excellent yields, cost savings, texture, flavor and nutrient profiles are possible. However, most soy protein concentrates lack sufficient solubility or sufficiently low viscosities to be used in brines for absorption or injection into whole muscle tissue. When legal standards for protein content exist (13), more concentrate must be used to achieve legal minimums. Brine viscosities increase and uniform distribution of brine components throughout the specific whole muscle piece is restricted. Finished product appearance and flavor are easily compromised. Thus, use of soy protein concentrates in whole muscle applications is limited. 

The huge variety of emulsions used as food, medicinal, cosmetic, and other industrial products make these colloids important practical systems in which the surface monolayers exert considerable influence. We have already discussed the use of lecithin to control the viscosity and the texture of chocolate in Vignette IV in Chapter 4. 

The texture of an emulsion frequently reflects that of the external phase. Thus O/W emulsions usually feel watery or creamy while W/O emulsions feel oily or greasy . This distinction becomes less evident as the emulsion viscosity increases, so that a very viscous O/W emulsion may feel oily. 

The concentration of droplets in an emulsion is one of the key parameters influencing its appearance, texture, stability, and flavor. For example, opacity, viscosity, and creaming stability of emulsions usually increase as the droplet concentration increases. The droplet concentration is normally expressed in terms of the disperse-phase volume fraction (< )), which is equal to the volume of emulsion droplets (Vd) divided by the total volume of the emulsion (Ve) < ) = Vd/Ve- Nevertheless, it can also be expressed in terms of the disperse-phase mass fraction (( )nj), which is equal to the mass of emulsion droplets (Md) divided by the total mass of the emulsion (Me) = M-q/Me- The mass fraction can be related to the volume... 

The effects of added poultry fat and type of binder on the texture of cooked chunks were investigated by Polo et al. (2007). Figure 11.5 illustrates the relationship between the hardness of the chunk and the poultry fat content for a recipe containing spray-dried animal plasma (SDAP) and WG as the binders. The resnlts showed that the hardness of the chunk decreased with an increase in the level of fat addition, indicating that the fat reduced the viscosity of the emulsion. Nevertheless, the hardness of the chunk containing SDAP was greater than that of the chunk containing WG. 

Mayonnaise and sauces vary widely in their composition, texture, and flavor, but they are all 0/W emulsions. The distribution of the two phases has an impact on the stability and texture of the product. A full-fat mayonnaise contains the same volume fraction of fat as margarine, but is the reverse type of emulsion. The distribution of the dispersed fat phase, the size of droplets, as well as the amount of fat crystals and the interaction between droplets influence the properties of the product. The size of the oil droplets is primarily affected by the emulsifying equipment and the viscosity of the water phase. 

The main positive functions of phospholipids in foods are their surface-active properties. They act as emulsifiers and stabilizers of emulsions (van Nieuwenhuyzen and Szuhaj, 1998), facilitate the dispersion of solid particles in the water phase, and improve the texture of multiphase food materials. Phospholipids make the texture smooth and improve the pleasantness by increasing the viscosity. The food tastes full and homogeneous. The bitter taste is also suppressed, but other tastes are not affected. 

In Chapter 17, we discuss rheological properties, in particular viscosity and elasticity, of colloidal systems. These properties are at the basis of quality characteristics such as strength, pliancy, fluidity, texture, and other mechanical properties of various materials and products. In addition to bulk rheology, rheological features of interfaces are discussed. Interfacial rheological behavior is crucial for the existence of deformable dispersed particles in emulsions and foams. Emulsions and foams, notably their formation and stabilization, are considered in more detail in Chapter 18. 

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