To determine if a freshly boiled but old egg has gone bad, you can use your senses and perform a few simple tests. Here are some methods you can follow:
Smell: Give the egg a sniff. If it emits a strong, unpleasant, or sulfur-like odor, it may have gone bad. Fresh eggs typically have little to no smell.
Inspect the Shell: Look for any visible cracks or damage on the egg's shell. If there are cracks, bacteria might have entered the egg, causing it to spoil.
Check the White and Yolk: Once you peel the egg, examine the egg white and yolk. If the egg white appears watery, slimy, or discolored, and the yolk looks greenish or greenish-gray, the egg has likely gone bad.
Float Test: Place the egg in a bowl of water. Fresh eggs generally sink to the bottom and lie flat on their sides. If the egg stands upright on the bottom or floats to the top, it may be unsafe to eat. The floating occurs when gas builds up inside the egg as it ages, making it buoyant.
Egg Rotating Test: Gently spin the egg on a flat surface. If it spins smoothly, it's likely good to eat. If it wobbles or doesn't spin smoothly, it might be spoiled.
Keep in mind that while these methods can give you an indication of the egg's freshness, they are not foolproof. If you have any doubts about the safety of the egg, it's best to err on the side of caution and discard it to avoid the risk of foodborne illness. Also, always ensure you store eggs properly in the refrigerator and use them before their expiration date for the best quality and safety.