Emulsions are surprisingly unstable. If they are not prepared in the recommended way, the emulsion is
unlikely to be stable and will tend to separate out.
In order to ensure maximum emulsion stability, the emulsion should be prepared in the following way:
(The guidelines below are designed to stabilize oil in water emulsions, since these are the sort of
emulsion most commonly found in the kitchen).
1. The most successful emulsions are prepared by adding the fat phase to the water phase little
by little. Adding the fat source little by little rather than in one go is recommended because if
only a little bit of fat is added initially, only a small amount of fat will be present in a large
amount of water, and in this situation it is much easier to divide the fat into tiny droplets. Also,
the tensioactive molecules will surround the fat droplets more quickly and more evenly if the
fat is initially at a low concentration. Equally, as more fat is added, these previously separated
small droplets further help to dissociate the large droplets that are being added into smaller
2. The mixture should be whisked constantly while the fat phase is added. Constantly whisking
the mixture as the fat source is added ensures that the fat droplets are separated into very
small droplets, which are more likely to distribute themselves evenly in the water phase.
Constant mixing also helps ensure that these droplets are evenly coated by the tensioactive
Changes to the mixture:
As fat is added, the mixture gradually thickens. This is because as the fat droplets become more and
more numerous, and smaller and smaller, they will disperse themselves throughout the entire water
phase and occupy almost all of it, reducing the subsequent ability of the water molecules in the water
phase to flow, and therefore increasing the viscosity of the mixture. The more fat that is added, the
thicker the final emulsion will be, however, if more fat is added than there is water present, an