Emulsion stability, effect sodium chloride

The third mechanism by which proteins affect the stability of emulsions is rheological. This mechanism derives fundamentally from electrostatic and steric effects. The importance of viscosity has been described earlier. The viscosity of a caseinate solution is, inter alia, an indicator of the degree of bound water absorbed by the hydrophilic groups, as well as the water trapped inside the molecular aggregates (Korolczuk, 1982). The viscosity parameters (K, apparent viscosity at zero shear stress n, the power law factor and o-y, the yield stress) of sodium caseinate have been studied and found to be affected by concentration (Hermansson, 1975), precipitation and solution pH of caseinate (Hayes and Muller, 1961 Korolczuk, 1982), de-naturation (Hayes and Muller, 1961 Canton and Mulvihill, 1982), sodium chloride (Hermansson, 1975 Creamer, 1985), calcium chloride (Hayes and Muller, 1961) and temperature (Korolczuk, 1982). 

A closer relationship between foam stability and HLB has been reported for two- or three-phase systems surfactant solution-oil or oil-surfactant phase-water [60,109-111]. The effect of various parameters changing HLB on the stability of foams and emulsions has been studied in [111]. These were the concentration of amyl alcohol and sodium chloride, the number of the ethylene oxide groups in the molecule of the oxyethylated octylphenol. As a general parameter of HLB the authors used the surfactant affinity difference concept (SAD) which is an empirical generalised formulation. It measures the deviation from the optimum formulation for three phase behaviour. For anionic surfactants... 

In Fig. 10 the interfacial tension and the stability of concentrated emulsions containing styrene and an aqueous sodium chloride solution are plotted against the concentration of sodium chloride. The w/o concentrated emulsions are stable for both Span 20 and Span 80. When SDS was used as surfactant, the o/w concentrated emulsions were more unstable at 50 °C than the above w/o concentrated emulsions because the double layer repulsion between cells is shielded by the high ionic strength. With SDS, concentrated emulsions did not form at room temperature above a salt concentration of 1.2 moll-1 because of the salting-out effect. The o/w concentrated emulsion did not form at all at 25 °C when Span 20 was employed as surfactant. 

Very few studies have focused on the stability of OAV emulsions in porous media. Sarbar et al. 24) conducted a study to determine the effect of chemical additives on the stability of OAV emulsion flow through porous media. They injected 1, 5, and 10% OAV emulsions in sand packs with varying pH and surfactant concentrations and found that there was an optimal value of the surfactant concentration at which emulsions were the most stable. Addition of sodium chloride to the aqueous phase had a detrimental effect on the stability of the emulsion. For their system they found that there... 

Release of methotrexate, metoclopramide and sodium chloride from type A, B and C w/isopropyl myristate/w emulsions have been compared (Fig. 5 a,b,c). In all cases, release from the type C emulsion is not prolonged, which may be a reflection of stability or structure or a combination of these two parameters. In the case of methotrexate, variation of the concentration of secondary surfactant (polysorbate 80) from 0.5 to 20% had no significant effect on the rate of drug release from the system. 

The objective of the experiments presented here is to investigate effects of sodium hydroxide and sodium chloride on emulsion stability, and to establish the dynamics of spontaneous emulsification in a caustic system. 

Srinivasan, M., Singh, H. and Munro, P.A. (2000) The effect of sodium chloride on the formation and stability of sodium caseinate emulsions. Food Hydrocolloid., 14,497. 

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