It makes no sense to pick eggs with eggshells

2017-10-26 health report, deputy director of the food and nutrition information exchange center of the national bureau of food and nutrition information

      In the evolution of animals, the occurrence of eggs is of great significance, which greatly improves the survival rate of offspring. The eggs of the reptiles are mostly white, such as turtle eggs and crocodile eggs, but birds have many different colors and stripes. Archeological studies have found that the ancient dinosaurs (the ancestors of birds) had eggs, which was also the evolutionary result of protecting future generations. If the egg is buried in the sand, the color of the egg does not matter. But if an open nest egg is made, the color and markings of the eggshell can be used as camouflage. Quail's nest in the grass, for example, its eggs are like camouflage; Woodpeckers are middle eggs in tree holes. Eggs are white. The markings of the eggshells can also be used as markers for the identification of the mother bird, especially those who prefer to get together to have a baby.

      The color of eggshells comes from two substances: protoporphyrin and biliverin (including biliverine combined with zinc). The shells are different in proportion to each other. Among them, the protoporphyrin produces yellow, red and brown, and biliverine produces blue and purple and green. The formation of biliverine is mainly in the process of metabolism, the old red blood cells are produced when the liver is destroyed, and the protoporphyrin is mainly composed of the fallopian tube cells of the chicken. Of course, there is also the idea that the protoporphyrin also comes from the destruction of red blood cells.

      The formation of eggs is made from a layer of introvert. The egg yolks are formed first, then the egg whites are formed, followed by a thin layer of keratin covering the egg yolk and egg whites. Later, in the fallopian tubes, calcium carbonate, magnesium carbonate and other substances are deposited in the albumin membrane to form hardened eggshells.

      The real color of the eggshell is only the very thin layer of the outer layer, and at the end of the formation of the shell, some cells in the fallopian tubes secrete pigment to "color" the shell. The process of "coloring" is like brushing the wall, layer by layer. Finally, the spots and patterns are painted. If the egg is still at rest, it will form a speck. If the egg is turning, it can form a stripe.

      Eggshell color is closely related to the breed, which can be inherited like white, black and yellow. At present, the domestic eggs are mainly imported from Roman brown, helan brown, hex - hex, etc., and about 85% of the eggs are reddish-brown.

For the same breed of eggs, the darker the shell, the harder the eggshell, and the loss of "ground and ground" in the transportation and storage process. Farmers in order to make an egg more hard, calcium in feed, but if you give too much chicken filling calcium, can make the egg surface frost, eggshell color becomes shallow, and raised calcification particles may occur.

      What are the implications for consumer choice? Actually egg nutrition mainly depends on the ratio of feed nutrition, although the iron, copper, vitamin B12, vitamin D, vitamin E and other nutrients, has certain influence to the eggshell color, but because is indirect impact, so little impact. According to the study data, the differences in the color of eggshells did not lead to significant differences in nutrition, and the nutritional differences between different color eggs were not significant. That is, there is no scientific basis for picking eggs with eggshells.