The ingredients used for whipping should be kept cool before whipping - colder fat droplets will stick to
each other more easily as they congeal, stabilising the air bubbles more effectively in their network. If
the cream is too warm, the fat droplets will not adhere to each other as well, so the mousse is more
likely to collapse. Also, a cold cream will have a higher viscosity than a warm cream (viscosity
increases on cooling as the fats congeal). to further increase their viscosity (cooled fats congeal
increasing viscosity). Increasing viscosity helps stabilise a mousse - if the cream is viscous, the rising
of the air bubbles to the surface is slowed down, so the introduced air bubbles are less likely to rise
and escape. This is also why the thickest cream possible is used.
If a cream is over whisked however, the fat droplets may start to join together, and form lumps. The air
bubbles will be less strongly held by the fat and the cream will lose volume.
Thickening sauces with cream
As explained above, cream is often added to sauces to thicken them. But these sauces will often
contain salt and acid that would usually cause the casein proteins to coagulate, so cream is usually
added to sauces at the last minute to prevent curdling.
However, cream with a very high fat content can be added to a sauce without fear of coagulation. This
is because as the cream is heated, the fat droplets (which are in relatively high concentration) will tend
to attach themselves onto the casein proteins (which are in relatively low concentration), and since the
fat content is sufficiently high in this type of cream, most of the proteins will be attached to the fat, and
are therefore less likely to attach to each other, which would cause the sauce to curdle. Similarly, a
skin is much less likely to form when these types of cream are heated, due to their relatively low
Yoghurt and cheese
In the presence of acid
When the pH of milk is reduced to about 5, the casein micelles will lose their negative charge and will