The yolk is the yellow part inside the egg, contrary to protein. Most of the protein in eggs is concentrated in the egg white and egg membrane, while the rest of the nutrients are concentrated in the yolk.
Egg yolk will solidify into a solid when heated. The main components of egg yolk are 17.5% protein, 32.5% fat, about 48% water, 2% minerals and various vitamins. It is very beneficial to the growth of mankind.
Which eggs can't be eaten
1. Cracked eggs: During transportation, storage and packaging, some eggs will crack and crack due to vibration, extrusion and other reasons, which are easy to be invaded by bacteria. If they are left for a long time, they are not suitable for eating.
2. Sticky shell egg: This kind of egg has a tough and weak yolk membrane due to long storage time, and the yolk is close to the eggshell. If it is partially red, it can be eaten, but if the egg membrane is close to the eggshell, it is dark black outside the skin and smells, so it is not suitable for eating.
3. Rotten eggs: As bacteria invade and multiply in the eggs, the eggs will deteriorate, and the eggshells will be dark gray, or even broken due to the expansion of hydrogen sulfide gas inside. If the mixture in the eggs is grayish green or dark yellow with a bad smell, you can't eat the eggs, otherwise it will cause bacterial food poisoning.
4, scattered yellow eggs: due to fierce vibration such as transportation, the yolk membrane is broken, causing mechanical yellowing; Or stored for too long, bacteria or molds invade the egg body through the pores of the eggshell, destroying the protein structure and causing the egg liquid to be yellow and turbid. If the yellowing is not serious and there is no odor, it can still be eaten after high temperature treatment such as boiling. However, if bacteria multiply in eggs, protein has degenerated, and it cannot be eaten with odor.
5, stillborn eggs: eggs in the incubation process due to bacterial or parasitic pollution, coupled with poor temperature, humidity and other reasons, resulting in embryonic development is called stillborn eggs. The nutrition of this egg has changed. If you die for a long time, protein will decompose and produce a variety of toxic substances, so it is not suitable for eating.
6, moldy eggs: Some eggs are rained or wet, which will wash off the protective film on the surface of the eggshell, so that bacteria invade the inside of the egg and become moldy, leading to black spots and moldy on the eggshell. This kind of egg is not suitable for purchase either.