Because preserved eggs are made of duck eggs wrapped in soda ash, lime, salt and lead oxide, duck eggs contain lead, which may cause lead poisoning if eaten frequently. This will lead to insomnia, inattention, anemia, joint pain, mental retardation, brain function and other symptoms. In addition, lead will replace calcium, affect calcium intake, and may also cause calcium deficiency.
Hygiene and nutrition of preserved eggs
It is often said that preserved eggs can't be eaten. In fact, it is mainly the doubt that preserved eggs contain heavy metal lead, but there is no need to be too alarmed, because a little attention can be avoided when buying again. Remember to check whether there are black spots of different sizes on the surface of the shell. If there is, avoid eating it.
Make preserved eggs
The key is whether the protein is completely gelled, so it must be soaked in a strong alkali solution in the production process to realize the denaturation of protein and produce a special flavor and color. However, in order to avoid the deterioration of the finished product caused by re-liquefaction after gelation, lead oxide, copper sulfate and methionine are usually added to the alkali solution to prevent re-liquefaction. The suspected lead residue is the residue of this chemical in the eggshell.
Nutritional value of preserved eggs
Generally speaking, it is rich in iron, methionine (an essential amino acid) and vitamin E (compared with eggs). Disadvantages: protein denatured by alkaline solution is not easily absorbed, and LAL in denatured protein has unconfirmed nephropathy in animal experiments.
The author's personal point of view: Preserved eggs are considered as a kind of food to increase daily diet changes and taste special flavor, but from the nutritional value, there seems to be other better choices. As for the problem of lead residue, consumers can only judge by appearance at present, but I already know that many experts in the food industry have developed a method to keep the quality of preserved eggs by controlling the temperature without adding lead oxide. I believe that in the near future, consumers can eat preserved eggs without worrying about heavy metal residues.