Rescues · TO TEMPER
Sour cream or yogurt curdles into grains in a hot pan.
Why it happens
Added cold and straight into heat. Acidified dairy is already close to curdling; heat shock finishes the job.
Recovering it
A lightly scrambled custard can often be saved by straining and blending immediately — you are breaking the curds up before they set further. A broken cheese sauce comes back with a splash of cold liquid whisked in off the heat, which drops it below the coagulation point and adds fresh protein at once. Seized chocolate can be loosened by adding more liquid deliberately, though it will no longer set the way it would have. Once a custard has fully set into solid curds, nothing recovers it.
The 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.
The full TO TEMPER lesson — how to tell, where to practise it, what it carries to.