The temperature during cook of egg is much more important than the most of folks reckon. Only some degrees separate soft, creamy egg of rubbery.
White of egg start to thicken at 63°C (145°F) and become soft solid at 65°C (150°F). That solidifying happen mainly because of the protein ovotransferrin, that is the most sensitive to heat, although it forms only 12 % of the whole protein. Proteins of the yolk thicken from 65°C and set at 70°C (158°F). Mix of white and yolk stabilize around 73°C (165°F). If eggs cook at 100°C too long, they become rubbery, because proteins continuously clot and water pushes between the molecules.
How Heat Changes Eggs
At 82°C and higher, the protein links become more tight in higher temperatures. White of egg becomes firmer, dry and rubbery. Then emerge hydrogen sulphide, that gives rotten egg smell.
FDA advises to cook eggs at 71°C (160°F) for safety. Some guidelines in United States require that white and yolk be firm, not liquid. Others simply say to cook everything at 71°C. Pots and dishes with eggs require internal temperature at least 160°F. Thermometer for foods ensures that the heat is reachd.
In recipes with other ingredients diluting the eggs by means of milk or sugar and cooking until 160°F kill harmful bacteria.
For soft-boiled egg the best range is 70 (75°C (158, 167°F)). Precise control, for instance by means of sous vide, allow miracles. For instance, 64°C during one hour give perfectly soft-cooked egg.
For fried eggs in butter use relatively cool pan. Cook on low heat in 135, 150°C, for have soft white below and smooth with brown edge up. Omelettes and scrambles benefit of higher heat for fast cook.
Start pan in 160°C and add eggs, that works well. Widely low temperature is the best. Low heat bans water evaporation and help to keep the eggs moist.
Eggs at room temperature before cook eases full cook of whites without overheating of the yolk. Cold eggs directly in hot water risk thermal shock. For soft-boiled meringue on warm cake bake in preheated oven in 175°C until 71°C inwardly, while around 15 minutes.