They are present in many dairy foods, including mayonnaise, creamers, whippable toppings, ice creams, etc. The o/w emulsions are probably the most versatile, and their properties are controlled by both the surfactants and the composition of the aqueous phase. Other emulsions that are employed include water-in-oil emulsions (w/o), where water droplets are dispersed in an oil, and water-in-oil-in-water (w/o/w) emulsions, which consist of an o/w emulsion whose droplets themselves contain water droplets. Anionic surfactants such as sodium dodecyl sulphate (SDS) are less frequently used to avoid electrostatic repulsions with the electrolytes present in water (e.g., NaCl, H 3O +), and cationic surfactants such as cetyltrimethylammoium bromide (CTAB) are never used.Įmulsions are widely used in the preparation of emulsified foods because lipids are mostly present in foods in the form of oil-in-water emulsions, where the oil droplets are dispersed in an aqueous solution. For this purpose, a recently developed methodology was employed, and experimental results were interpreted on the grounds of a pseudophase kinetic model.Ĭhemical structures of nonionic and zwitterionic surfactants commonly employed in the preparation of foodstuffs. In this work, we analyze the effects of the surfactant Tween 20 on the oxidative stability and on the effective concentrations of two model antioxidants derived from cinnamic acid, determining their interfacial concentrations in the intact emulsions to avoid disrupting the existing equilibria and biasing results. The rate of the inhibition reaction depends on the effective concentrations of antioxidants, which are mostly controlled by the amount of surfactant employed in the preparation of the emulsion. This is the case, for instance, in the inhibition reaction between antioxidants and the lipid radicals formed in the course of the spontaneous oxidation reaction of unsaturated lipids, which are commonly employed in the preparation of food-grade emulsions. However, addition of surfactants to binary oil-water mixtures also brings up the formation of three-dimensional interfacial layers, surrounding each emulsion droplet, that significantly alter chemical reactivity. They play two main roles in the emulsification processes: first they decrease the interfacial tension between the oil and water, facilitating droplet deformation and rupture second, they reduce droplet coalescence by forming steric barriers. The proposed equation gives good correlation between the measured viscosities of water-in-oil emulsions as a function of temperature and the volume fraction of water.Surfactants have been used for decades in the food industry for the preparation of lipid-based emulsified food stuffs. The ASTM equation, method D-341, for describing viscosity as a function of temperature is extended to include the variation of dispersed phase volume fraction. Using six different crude oils, the effective viscosities of several synthetic water-in-oil emulsions are measured at atmospheric pressure using a dynamic viscosimeter for different shear rates, temperatures and volume fractions of the dispersed phase. The effective viscosity of water-in-oil emulsions depends mainly on the volume fraction of dispersed phase and temperature, along with several minor effects, such as shear rate, average droplet size, droplet size distribution, viscosity and density of oil. Water-in-oil emulsions are important in the petroleum industry in production operations, where the water content of the emulsion can be as high as 60% in volume, also in petroleum refining operations where generally the water content is low.
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