Bringing something delicate up to the temperature of something hot in stages, so it never meets the shock that would ruin it.
Technique at a glance
A compact visual model of the lesson. Use the full mechanism and success criteria below when you practice.
Concept
Bringing something delicate up to the temperature of something hot in stages, so it never meets the shock that would ruin it.
What changes
Egg proteins begin to set around 65°C and are firmly coagulated by about 73°C.
What good looks like
The tempered mixture thins slightly and warms to the touch of a finger on the outside of the bowl, with no lumps forming.
Practice counts when you cook
Reading this brief does not change your School state. Finish a real practice dish in Cook mode and log the cook; that cook is the evidence that advances the skill.
What to focus on
Mechanism
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.
Success criteria
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.
Failure guards
Scrambled specks in a custard or sauce.
Hot liquid added too fast, or the mixture went above about 73°C. The egg proteins coagulated locally before the whisk could distribute the heat.
A cheese sauce turns stringy with an oily slick.
Held above roughly 65°C. The casein network contracts and squeezes out the butterfat it had been holding.
Sour cream or yogurt curdles into grains in a hot pan.
Added cold and straight into heat. Acidified dairy is already close to curdling; heat shock finishes the job.