| The stability of sodium caseinate (CN) stabilized emulsions influenced by flaxseed gum(FG) at both neutral and acid conditions was studied in this research. At the same time, effectsNaCl on the stability of the emulsion was also studied. Finally, we use the FG as the stabilizerand added it into the double emulsion, for the purpose of increasing the stability of theW1/O/W2emulsion and enhanced the encapsulation efficiency.First, the influence of FG on the stability of CN-stabilized emulsions was investigated.State diagram was used to figure out the phase behavior of CN with different concentration ofFG and pH. From the result, the interaction between FG and CN in neutral conditions wasmainly the hydrophobic, it can only form the weak complexes. Emulsions were prepared atthis situation, there was electrostatic repulsion between FG and CN molecules since both ofthem were negatively charged. When the FG concentration was low (<0.3%), depletion wasthe mainly factor that made the emulsion unstable. With the increasing amount of FG, theweak gel properties of FG helped to increase the stability of the emulsion.Effect of FG on the adsorption properties of CN at the oil-water interface and itsfunctions on the stability of oil-in-water emulsions stabilized by CN at pH5.5were studied.Dynamic surface pressure measurements were performed as a function of FG concentrationranged from0to0.3wt%. Surface pressure of the FG-CN solution at the oil-water interfacereached the highest when the FG was0.1wt%. The diffusion rate (kdiff) of the CN to theinterface increased with the increase of FG, while the rates of penetration (kP) andrearrangement (kR) of CN at the interface decreased. Properties of the emulsions were alsoinvestigated. The stability of emulsion was improved when the FG concentration reached0.1wt%, but decreased due to depletion flocculation caused by the more unabsorbed FG when theFG concentration reached0.2and0.3wt%. CLSM revealed the pronounced effects of FGwhich affected the microstructure of the emulsion. Surface protein concentration showed adecrease with the increasing FG concentration and no obvious difference in proteincomposition was found.pH value and ionic strength are the two important facts that affect the stability of theemulsions. We discussed the interactions between FG and CN in aqueous solution by makingthe state diagram, and then in emulsions by measuring the ζ-potential, droplet size,microstructures, apparent viscosity and surface protein composition, showing the possiblerelationship between FG-CN interactions and the stability of the emulsions. At pH7,emulsions could be stable for a long time without the addition of NaCl due to FG’s weak gel-like properties. With the increasing amount of NaCl, the electrostatic shielding effectmade the emulsions’ ζ-potential decreased as well as their viscosity, but their depletionflocculation did not improved, NaCl made the samples unstable. When at pH5, emulsionswithout the addition of NaCl were unstable because of the pH was very close to the isoelectricpoint of CN. NaCl helped the FG adsorb onto the surface of the CN-coated droplets, and lowaddition of NaCl improved the stability of the sample.We used the FG as stabilizer and studied the effects of FG on the stability and theencapsulation stability of the W1/O/W2emulsion. From the result, FG could help to increasethe stability of emulsion and increase the viscosity. It can also help to increase theencapsulation efficiency as well as the encapsulation stability of such emulsions. |
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