[Jay_Johnston]

I have been trying to create an emulsion but i am having trouble keeping it stable, the emulsion consists of -

50g/litre citric acid (suspended in the water)
20g/litre PVP K-30 (suspended in the water)
200ml/litre Veg oil
200ml/litre tween 20
600ml/litre water

All ingredients are heated to around 70 degrees before mixing.

Once mixed i am always left with one fifth of the the mix separating from the emulsion?   

 

[Arkcon]

Its a shame the Tween 20 isn't helping you enough, it is an emulsifier.  Perhaps your formulation simply needs more Tween, if possible.  You might try adding some ionic salt -- that might coat the droplets with charged groups, and help the droplets repel each other.  You might also try using ultrasound, particularly an immersible ultrasonic lance, to make droplets.  But I am rapidly getting out of my depth here, someone else may be by soon with better ideas.

[Enthalpy]

Egg yolk? But this one shouldn't be heated to 70°C before.

[EastPA]

I have been trying to create an emulsion but i am having trouble keeping it stable, the emulsion consists of -

50g/litre citric acid (suspended in the water)
20g/litre PVP K-30 (suspended in the water)
200ml/litre Veg oil
200ml/litre tween 20
600ml/litre water

All ingredients are heated to around 70 degrees before mixing.

Once mixed i am always left with one fifth of the the mix separating from the emulsion?

PVP is water soluble (dissolved like the citric acid?)
If you are tring to suspend insoluble PVP in a liquid, there will be difficultly if the particle size is high or the liquid viscosity is low.  Perry's has terminal settling velocities for particles based on particle size, density and fluid viscosity.   Provide those values and settling can be estimated.  The emulsifier or wetting agent is used to separate the insoluble particles so their apparent diameter is that of a single particle vs an agglomerate (mechanical bond) or flocculant (Steric bond) collection of particles

[Furanone]

Tween 20 has good emulsification activity but fairly poor emulsification stability. Amphiphilic proteins are the reverse -- average emulsification activity but better emulsification stability since they are larger than Tween molecules and while Tween can coat the oil droplets better all around they will easily join into each other (coalescence) while proteins (usually denatured or partially denatured) are longer chains that can go in and out of oil and water phases like a snake and prevent oil droplets from aggregating.

I would suggest cutting down the tween 20 and add in sodium caseinate (a very good emulsifying protein from milk) to offset.

Also if you do not have any viscosity constraints, you can dramatically increase the emulsion stability by increasing viscosity of the continuous water phase by adding in like 0.25-0.4% xanthan. Other things to consider based on the Stokes-Einstein equation, the main parameters to increasing emulsion stability are by increasing viscosity of continuous phase (ie add small amount of xanthan), decrease the difference in densities between the continuous (water) phase and the dispersed (oil) phase (ie use up to 3% brominated vegetable oil to increase density to close to water), or decrease the oil droplet size of your dispersed phase with better homogenization.