Why is there heavy metal lead in preserved eggs? Thank you, everyone.

In the traditional preserved egg making process, heavy metals such as lead or copper are often added to the dipping solution to solidify protein. According to the regulations of Taiwan Province Provincial Health Department, the lead content of preserved eggs should not exceed 2ppm, and the copper content should not exceed 8ppm. Moreover, agricultural administrative units also help manufacturers to produce excellent preserved eggs, so that the lead content does not exceed 0.3ppm and the copper content does not exceed 5ppm. Therefore, most of the soaking solutions of qualified manufacturers do not add heavy metals or have little content. But now there are lead-free preserved eggs. Let me introduce again: many people know that preserved eggs contain lead, so everyone buys lead-free preserved eggs, thinking that they can be safely eaten. In fact, lead-free preserved eggs also contain lead, which is ok for adults, but children should eat less. When processing preserved eggs, soda ash, lime, salt and yellow lead powder should be mixed in a certain proportion, and mud and bran should be wrapped outside the duck eggs. Two weeks later, the delicious preserved eggs are ready. Plumbum preparatium powder is lead oxide, which can make eggs produce beautiful patterns, but with Plumbum preparatium powder, preserved eggs will be polluted by lead. According to the national regulations, the lead content of preserved eggs per1000g should not exceed 3mg, and preserved eggs that meet this standard are also called lead-free preserved eggs. Therefore, "lead-free preserved eggs" are not lead-free, but lead content is lower than the national standard. Chinese medicine believes that children's bodies are "young yin and young yang" and their metabolism is extremely vigorous. Trace lead in "lead-free" eggs will remain in tissues such as liver, lung, kidney, brain and red blood cells after being absorbed by children, and will also cause calcium loss in bones and teeth. Regular consumption of "lead-free preserved eggs" will cause bone and tooth dysplasia, loss of appetite, gastroenteritis and so on. In children, it will also affect intellectual development. Lead-free preserved eggs are delicious and nutritious, but children are in a stage of vigorous physical development and have obvious reactions to the harm of lead, so it is better to eat less. Nutritional Value of Preserved Eggs The nutritional components of preserved eggs are similar to those of ordinary eggs. During the curing process, protein and lipids are decomposed, which makes them easier to digest and absorb, and the cholesterol is reduced. It is cured with iron agent, so the iron content is also high. However, vitamin B and essential amino acids were destroyed. Are preserved eggs more nutritious? Songhua preserved eggs are characterized by white needle-like crystals in protein, which some people think are particularly nutritious. This is because iron phosphate is added in the processing. Therefore, compared with ordinary preserved eggs, only the iron content is higher, and there is no difference in other nutrients. How to buy preserved eggs? At present, preserved eggs on the market are duck eggs or preserved eggs, which can be selected according to personal preferences. When buying preserved eggs, you can pay attention to whether there is a quality certification mark. In addition, preserved eggs with high lead and copper content will have more spots on the eggshell surface, and after hulling, you can also see that the protein is dark green or occasionally has black spots, which is not suitable for purchase. Some preserved eggs made by traditional methods will be wrapped in red soil and straw, which is unsanitary and inconvenient to judge the lead content by appearance, and is not suitable for purchase. It is recommended to buy products with complete packaging and clear labels. Pay attention to the date of production when buying, and pay attention to the way and period of preservation when going home to save. Supplement: the harm of lead to human body: 1, strong neurotoxicity: lead can damage brain and nerve, making people mentally retarded, slow to respond, hyperactive, inattentive, hearing loss, learning difficulties and dyskinesia. 2, cause anemia 3, inhibit immunity 4, loss of appetite, unexplained abdominal pain, vomiting, diarrhea or defecation 5, affect the absorption and utilization of minerals and vitamins. Lead to calcium deficiency, zinc deficiency, iron deficiency and so on. But eating preserved eggs may also cause poisoning. In summer, the weather is very hot. Most people like to entertain themselves with preserved eggs while drinking beer, or entertain the whole family with preserved eggs in cold sauce. It may never occur to them that preserved eggs may also cause food poisoning. According to the inspection and analysis of relevant food experts, there are only 400-500 bacteria on clean eggshells, while there are as many as10.40-0.40 billion bacteria on dirty eggshells. If these bacteria enter the egg in large quantities through the pores of the eggshell, eating such preserved eggs will be poisoned. When buying preserved eggs, it should be noted that the protein of preserved eggs is dark brown transparent body after peeling, which has certain toughness; Contaminated preserved eggs are light green, with poor toughness and easy loosening. Such preserved eggs must not be eaten. Salmonella is the main bacterium that pollutes preserved eggs. After it enters the human body with preserved eggs, it causes inflammation on the intestinal trace membrane. After bacterial division, it will produce highly toxic endotoxin, which will cause poisoning symptoms. Experiments have confirmed that Salmonella will die immediately at a high temperature of 100 degrees Celsius, at 70 degrees Celsius for 5 minutes, and at 60 degrees Celsius 15-30 minutes. Therefore, when eating suspicious preserved eggs, you can steam the shelled eggs at high temperature for about 5 minutes, and then you can eat them safely after cooling. The suitable temperature for the growth of Salmonella is 20℃-37℃, and the temperature in summer and autumn is just within this range, so people should pay special attention to prevent preserved egg poisoning. The main symptoms of preserved egg poisoning are nausea, vomiting, headache, dizziness, abdominal pain and diarrhea. Many people like to eat preserved egg porridge, but it's okay to eat less preserved eggs, and it's not good for your health to eat too much. 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. How to eat preserved eggs: First of all, eating preserved eggs with ginger vinegar juice can not only neutralize alkalinity and remove alkaline astringency by using gingerol and acetic acid, but also destroy a toxic substance used in preserved egg production-plumbum preparatium powder and substances harmful to human body during protein decomposition of preserved eggs by using volatile oil and acetic acid contained in ginger vinegar juice. Teach you three ways to identify the appearance of preserved eggs (1). Observe whether its appearance is complete, damaged or mildewed. You can also feel its elasticity with your hands, or shake an egg to listen to its sound. The surface of a good preserved egg is completely covered with mud, without mildew spots, and the eggshell is intact without damage after peeling off the covering; Elasticity after peeling; There is no bump when shaking. The packaging materials of inferior preserved eggs are damaged or moldy; After peeling off the wrapping material, the eggshell has spots, damage and leakage, and some contents have been polluted; After shaking, there is a sound of water swinging or a feeling of light floating. (2) Identification by optical transmission. After peeling off the package, the preserved eggs were identified according to the light transmission method of fresh eggs, and the color, solidification state and air chamber size of the eggs were observed. The contents of inferior rubber balls are not solidified, but watery, with a large air chamber. (3) Have a taste. The whole preserved egg is solidified, not sticky, clean and elastic, translucent and brown, with loose patterns and textures; When the egg is cut vertically, you can see that the yolk is light brown or light yellow with a thin center. Inferior preserved eggs have a pungent or musty smell.