Clean shells prove little. Beneath an uncracked exterior, an egg can contain Salmonella because bacteria may enter its contents inside the hen, before the shell forms. Appearance offers no verdict. This route, known as vertical transmission, defeats the comforting assumption that contamination must leave a visible mark, and makes a spotless egg an unreliable witness to its own safety.
Runny yolks deserve skepticism. Although their texture does not prove that bacteria remain alive, it can indicate cooking that has not delivered enough heat throughout the egg to destroy Salmonella. Heat needs sufficient time. Thermal inactivation depends on both temperature and duration, which means a browned edge or a firm white cannot certify what happened at the center. Texture is not testing. Food safety guidance recommends cooking ordinary shell eggs until both yolk and white are firm, while egg dishes should reach an internal temperature of 160 degrees Fahrenheit, measured with a food thermometer.
Preference should not dictate protection. For recipes served raw or undercooked, pasteurized eggs offer a safer option because their treatment reduces Salmonella without requiring the finished dish to have a firm yolk. Cold storage helps too. Refrigeration at 40 degrees Fahrenheit or below limits bacterial growth, but does not sterilize an egg or undo contamination already present inside it. Some diners face more. Children, older adults, pregnant people and those with weakened immune systems should avoid raw or undercooked eggs because infection can have more serious consequences for them. The shell keeps its silence.
