denaturation. The resulting mixture will need to be heated, because the egg yolk proteins do not
denature as easily as egg white proteins. As the egg yolk proteins denature, they surround the
incorporated air bubbles, by exposing their hydrophobic parts. The mixture should be heated gently to
prevent egg yolk proteins from bonding to each other before they have denatured, which would
otherwise cause lumps to form and give the sabayon a taste of cooked eggs.
Use of eggs in cooking: how to use eggs as thickener
If egg yolks are added to water based sauce and the mixture is whisked with gentle heating, the sauce
will thicken. This is because the combination of the gentle heat and the mixing will cause the egg yolk
proteins to slowly denature and unwind. They then act to thicken the sauce by forming microscopic
curdles, that are packed into the water part of the sauce, reducing the flow of water (in a similar way to
the released starch molecules in flour thickened sauces).
If the mixture contains a large quantity of denatured egg yolk proteins, the denatured proteins may
begin to form bonds with each other, and further thicken the sauce by trapping the water molecules.
This is even more pronounced on cooling the sauce – the protein molecules will have less energy, so
will be moving more slowly and are more likely to form bonds, trapping water molecules.
The danger: Thickening with egg yolks is a delicate way to thicken a sauce – if...
The danger: Thickening with egg yolks is a delicate way to thicken a sauce – if the temperature is too
great, lumps will appear because the egg yolk proteins aggregates will clump together before they
have had a chance to denature and act to thicken the sauce. If large numbers of the proteins clump
together like this – the mixture may actually separate and curdle – the large mass of lumped together
proteins will actually separate itself from the liquid in the mixture.
Curdling may also occur is the mixture is heated for a long time at too high a temperature because
under these conditions the denatured proteins are more likely to coagulate, and prolonged heating will