Egg yolks coagulate at approximately which temperature?

• A. 52°C
• B. 66°C
• C. 72°C
• D. 78°C

Answer: (B)

When heat is applied, the proteins in the egg yolk unfold and link together to form a network that thickens the liquid. This coagulation begins around the mid-60s Celsius, roughly 65°C, and progresses toward firmer set as the temperature rises. A value of about 66°C sits right in that onset range, representing the soft-setting point of the yolk. If the temperature were significantly lower, coagulation wouldn’t occur yet and the yolk would stay runny. If it were much higher, the yolk would become clearly firm or solid, which is beyond the initial coagulation stage.