droplets, and make large “threads” that prevent coalescence.
One egg yolk contains enough protein and phospholipid molecules to make up to 60 litres of
mayonnaise. It is therefore not essential to use the whole yolk when making only a small bowl of
mayonnaise. However, the egg yolk also brings water to the mayonnaise, so if less egg yolk is being
used, more vinegar should be added, or alternatively some water should be added for a less strong
Failed egg yolk emulsions:
There are three main reasons why these specific emulsions are more likely to fail:
1. If the sauce is heated, the fat droplets will have more energy than if the emulsion was not
heated, so will move around more quickly. Quickly moving fat droplets are more likely to bump
into other fat droplets, and will bump into them with more strength. This bumping force is more
likely to overcome the stabilisation provided by the phospholipids than in a non-heated
emulsion, so the fat droplets are more likely to join up and separate the emulsion.
2. Like a mayonnaise, a bearnaise or hollandaise may also fail if the amount of water present in
the final emulsion is too low. As mentioned above, fat droplets need a certain quantity of water
present in order to disperse themselves. Too low a water content in relation to the fat content
is much more likely to be a problem in heated emulsions. Even if the appropriate quantities
were added at the beginning, some water may evaporate from the emulsion as it is heated,
unlike the fat, so the overall water quantity, compared to the fat quantity, will be too low.
3. The main reason that egg yolk based hot emulsions fail is because egg yolks contain proteins.
During rapid heating, these quickly moving proteins are likely to collide with each other and
stick together, forming solid lumps, before they have had the chance to denature. The risk of
lump formation can be reduced in two ways:
a) continuously stirring during emulsion preparation – this ensures that any such lumps that might
form will be reduced sufficiently in size by the whisking action that they will be hard to detect with the