During transportation, storage, and packaging, eggs can develop cracks or fractures due to vibrations, squeezing, and other reasons. This makes them highly susceptible to bacterial invasion. If stored for an extended period, they should not be consumed.
Stuck-to-the-Shell Eggs
In these eggs, the yolk membrane weakens after prolonged storage, causing the yolk to stick to the shell. If only a portion of the yolk is red, it may still be edible. However, if the yolk membrane is firmly stuck to the shell, the attached area is dark black, and there is an off odor, the egg should not be consumed.
Smelly Eggs
When bacteria invade the egg and multiply in large numbers, spoilage occurs. The eggshell becomes a dark grayish color, and it may even rupture due to the expansion of internal hydrogen sulfide gas. The egg's contents will be a grayish-green or dark yellow color with a foul odor. Such eggs are inedible and can cause bacterial food poisoning.
Broken-Yolk Eggs
These occur due to violent shaking during transportation, which mechanically ruptures the yolk membrane. Alternatively, if stored for too long, bacteria or molds can enter the egg through the pores in the shell, breaking down the protein structure and causing the yolk to break, resulting in thin and cloudy egg whites. If the yolk is not severely broken and there is no off odor, it can still be eaten after being thoroughly cooked at high temperatures. However, if bacteria have multiplied inside the egg, the proteins have denatured, and there is a foul odor, it should not be eaten.
Dead Embryo Eggs
These are eggs where the embryo's development has ceased during the incubation process, often due to bacterial or parasitic contamination, combined with unfavorable temperature and humidity conditions. The nutritional content of these eggs has changed. If the embryo has been dead for a long time, the proteins will decompose, producing various toxic substances, making them inedible.
Moldy Eggs
Some eggs are exposed to rain or moisture, which washes away the protective film on the shell surface, allowing bacteria to enter and cause the egg to spoil and mold. This results in black spots and mold on the shell, and such eggs should not be purchased or consumed.
Additionally, other types of eggs such as Yellow-Diaphegma Eggs and Blood-Streak Eggs should generally not be purchased or consumed.