When it goes wrong · Temper
A cheese sauce turns stringy with an oily slick.
Can you save it?
Reviewed for this symptom
Off the heat, whisk in a splash of cold milk or cream; the temperature drops below the point where the casein tightens, and the fat usually rejoins. If it stays oily, a teaspoon of cornflour slurry whisked in over low heat binds it.
How to confirm the diagnosis
Observable cues, not inferred user state
- Strings of cheese with fat pooling
- The sauce was hot or simmering when the cheese went in
- It was held on the heat after the cheese melted
Not this?
- Scrambled specks in a custard or sauce.
- Sour cream or yogurt curdles into grains in a hot pan.
- Melted chocolate seizes into a stiff paste.
- The cheesecake filling curdled and turned grainy.
What actually happened
Only this symptom
Held above roughly 65°C. The casein network contracts and squeezes out the butterfat it had been holding.
The full mechanism
Shared by every temper failure
Egg proteins begin to set around 65°C and are firmly coagulated by about 73°C. Dairy proteins clump when heated fast or in the presence of acid. Chocolate and cheese release their fat when their structure tightens. In each case the failure is not the final temperature but the rate of change at the point of contact: pour hot liquid into cold yolks and the yolks at the interface pass through the whole setting range instantly, while the rest of the bowl is still cold. Tempering removes the interface — you add the hot thing to the cold thing a little at a time, so the cold mixture's temperature rises gradually and no part of it is ever far ahead of the rest. The same reasoning covers stirring cheese into a sauce off the heat and letting cream come to room temperature before it meets a hot pan.
The full Temper lesson — how to tell, where to practise it, what it carries to.
Next time
Prevent this specific failure
Add cheese off the heat or at the lowest heat, and never let the sauce return to a simmer once it is in.
What right looks like
Shared by every temper failure
- The tempered mixture thins slightly and warms to the touch of a finger on the outside of the bowl, with no lumps forming.
- It stays glossy. Any dulling or graininess means proteins have started to set.
- When enough hot liquid has gone in, the two mixtures pour at the same speed — that is the point at which the rest can be combined all at once.
- For cheese, the shreds disappear into the sauce rather than stringing behind the spoon.