merely to make the fat droplets smaller and improve their dispersion, but a constant whisking
will prevent the temperature of the mayonnaise from getting too low, especially if the emulsion
is not heated, so will reduce the chances of fat droplets congealing. Ingredients to be used in
an emulsion should also be removed from the fridge in advance of preparing the emulsion, to
further eliminate this problem.
V/I - 3 (of 5)
Emulsions made with egg yolks
These emulsions contain proteins and phosholipids from the egg yolk, which act to stabilise a mixture
of water and fat.
Eggs used for egg based emulsions should be fresh - when eggs age, their phospholipid molecules
decompose into molecules of cholesterol. Cholesterol is not as good an emulsifier, because it does not
contain a pronounced charged region like in a phospholipid, so is less likely to stabilise the
incorporated fat droplets.
Presence of acid:
Acid is often added to emulsions containing phospholipids: - in an acidic medium, the presence of the
H+ ions between the fat droplets reduces the chances that the charged phosphate heads, which
extend from the fat droplets, will contact each other. Without acid, the surrounded fat droplets are less
likely to repel each other and the emulsion will be more likely to separate out.
Acidity also play an important role on protein structure. As proteins are probably more important than
phospholipids in emulsion making, acidity is important.
The exemplary mayonnaise
To make a mayonnaise, egg yolk is mixed with vinegar, salt and pepper. The water phase of the
mayonnaise is provided by the vinegar (which contains 80 % water) and the egg yolk (which contains
almost 50% water). The egg yolks main function is to provide a generous source of proteins and
As the oil is added, it is progressively introduced into the centre of the phospholipids micelles, and this
results in fat droplets that are surrounded by phospholipid membranes and are therefore very stably
dispersed in the water phase. At the same time, proteins denatured through whisking surround the oil