Why boiled eggs turn grey and whether they are still safe to eat

Boiled eggs occasionally develop a grey or green ring around the yolk, leading many to question its safety for consumption. Dietitian Dt Amreen Sheikh, from KIMS Hospitals Thane, reassures that there is no cause for alarm in most cases. Overcooking is typically the culprit behind this discoloration, as prolonged heat causes the sulphur in the egg white to react with iron in the yolk, forming iron sulphide. This explains the characteristic grey-green hue.

However, the colour change does not necessarily indicate spoilage. If the egg was fresh before cooking, prepared properly, and stored correctly, the ring is generally harmless, and the egg remains safe to eat. The downside of overcooking is that the yolk becomes drier, firmer, and less enjoyable in texture.

To prevent this, Sheikh advises cooking eggs just until they are set, then immediately transferring them to cold or ice water to halt the cooking process and simplify peeling. Eggs should be stored at room temperature for a limited time only. If a boiled egg has been left out for too long, has an off smell, or exhibits a slimy texture, it should not be consumed, even if the yolk appears discolored.

Despite the grey ring, Sheikh emphasizes that eggs are still nutritious, providing high-quality protein and essential nutrients like vitamin B12 and choline. The discoloration alone should not discourage consumption. In summary, a fresh, properly stored boiled egg with a grey ring is typically safe to eat, though discard it if there are signs of spoilage or uncertainty about storage.