Internet has circulated a small video in 2015 to rehype, the video mentioned two cases of food poisoning, and blamed the poisoning on eating long-spotted eggs, Even mention was made of the presence of salmonella, which can cause food poisoning, in long-spotted eggs.
So can eating freckled eggs really cause food poisoning? As a professional team engaged in quality and safety risk assessment of agricultural products, we can responsibly tell you that there is no inevitable link between spotted eggs and food poisoning!
Of course, the words “there is no inevitable connection” from the professional team are not persuasive. Next, experts will explain scientifically the formation of spotted eggs and use actual data to show the contamination and harm of salmonella.
Formation of spotted eggs.
There are two types of long-spotted eggs, one is the surface of our common eggshell can be seen with the naked eye touchable brown spots, and some spots even slightly raised, also known as freckle eggs; The other is a watermarked spot or strip on the bottom of the eggshell that is visible to the naked eye and dark in color. It is also known as a dark spotted egg or a bottom spotted egg (see right below).
The reason for the formation of freckled eggs is mainly due to the disorder of secretion of eggshell glands, because the pigment depth of brown-shell eggs is determined by the degree of pigment deposition in the outermost stratum corneum of the eggshell. These pigments are continuously secreted and deposited on the stratum corneum by the eggshell glands 3 to 5 hours before delivery. Eggshell gland secretion disorder, will cause uneven pigment deposition, the formation of so-called freckled eggs. On the other hand, the protruding spots on the surface of eggshells were caused by the disorder of calcium metabolism in laying hens, and the protruding spots were easier to attach to the pigment secreted by eggshell glands. However, the presence of such freckles did not affect the overall nutritional quality of the egg, just as a little abnormality in the mother chicken’s body would not affect the baby chicken’s basic health. Moreover, the eggshell and its outer and outer membranes exist precisely to protect the baby chicken. Most importantly, the formation of such freckles is not necessarily associated with contamination by pathogenic bacteria.
Dark spot eggs widely exist in white shell, pink shell, brown shell, green shell and other different color eggshell layers. Under the LED light source dark spots will become translucent color, so abroad also known as translucent eggs. The appearance of dark spots is influenced by many factors: there are no dark spots on the surface of newly laid eggs, and almost all dark spots can be seen on the surface of eggshells under natural light after storing for a week; at the same time, the appearance of dark spots is also influenced by the age of the chicken (the older the chicken, The larger the dark spot, the more the feed (0.4% P can reduce the incidence of dark spot), especially affected by the storage time, temperature and humidity. 4. 4% phosphorus can reduce the incidence of dark spot, especially by storage time and temperature and humidity. No dark spots were found in the newly laid eggs. After 2 to 3 days of storage, the dark spots could be clearly seen by photographing the eggs. After 1 week, the dark spots became more obvious. After the second week of storage, the dark spots did not increase. After 4 weeks, the dark spots would gradually disappear. In a certain range, the greater the temperature and humidity, the more serious the dark spots. According to the research and conclusion of scholars at home and abroad, it is considered that the root cause of dark spot formation of fresh eggshell is the poor toughness of eggshell membrane, which results in the water in shell passing through the shell membrane and accumulating in eggshell, and the appearance of dark spot has no significant effect on the quality of egg itself. It is not necessarily related to the contamination of pathogenic bacteria.
In addition, the long storage of eggs, the mold contamination may also form dark spots, but this light source irradiation is not transparent, and after opening the eggs, can be seen on the shell adhesion mold. Although this egg is not salmonella caused by dark spots, but also unsafe, can not be eaten.
Although there is no direct correlation between spoiled eggs and the contamination of pathogenic bacteria, in reality, there is still a risk of contamination of eggs by pathogenic bacteria. Egg shell itself has the function of protecting egg contents from bacterial infection, but there are dense stomata on the surface of egg shell, through which the egg controls the exchange of water and gas during embryonic development. Although an egg has four protective layers, the inner, outer, and outer layers of the eggshell, and the protective film on the surface of the eggshell to protect the egg from bacterial infection, washing the egg destroys the protective film on the surface of the eggshell.Chicken manure attached to the eggshell will dissolve the protective film on the surface, and the bacteria that may be carried in the washing water or feces may enter the eggshell through the stomata. In addition, the hands of people contaminated with pathogenic bacteria also break the protective film on the eggshell surface when they pick up eggs repeatedly, causing pathogenic bacteria to enter the eggshell through stomata. When the conditions are suitable, the pathogenic bacteria will further propagate and break through the inner and outer membrane to contaminate the egg content. Salmonella in chicken body has the characteristics of recessive carrying, that is, although the chicken carries salmonella, but does not show clinical symptoms, so the possibility of Salmonella contamination in eggs is higher than other pathogenic bacteria.
Harm and Prevention of Salmonella.
Although the contamination level of salmonella in eggs in China is very low, salmonella, as one of the most common food-borne pathogens, its harm is also obvious to all. It can cause acute gastroenteritis, the typical symptoms include fever, diarrhea, vomiting and so on, the condition can last for 4 to 7 days, and even lead to death in severe cases. About 1.4 million non-typhoid salmonella cases are reported in the United States each year, resulting in 168000 visits, 15000 hospitalizations and about 400 deaths. Similarly, salmonella food poisoning is the second most common cause of food-borne outbreaks in the EU (campylobacter food poisoning is the first). The foodborne diseases caused by salmonella ranked first among the bacterial foodborne diseases in China. From 2006 to 2010, 70% to 80% of reported outbreaks of bacterial foodborne diseases in China were caused by salmonella. Therefore, the harm of salmonella contamination in food should not be underestimated.
However, salmonella could be killed at 100 ℃ for 5 minutes at 70 ℃, 15 to 20 minutes at 65 ℃, and 1 hour at 60 ℃ for its poor heat tolerance. The results showed that Salmonella could be killed at 100 ℃ for 5 minutes, at 65 ℃ for 15 to 20 minutes, and at 60 ℃ for 1 hour. Therefore, when we eat eggs or other food, we can kill salmonella contamination by heating enough to ensure that our diet is safe. At the same time, the kitchen processing process should pay attention to the separation of raw and cooked to avoid cross-contamination, so as to effectively prevent the infection of salmonella.
What matters should be paid attention to in egg consumption?
Eggs can be contaminated not only by salmonella, but also by listeria, staphylococcus aureus and other pathogenic bacteria.Under normal circumstances, should be cooked as far as possible before consumption, do not recommend eating raw eggs.
The storage life of eggs varies greatly according to the different treatment methods. The United States requires producers to wash eggs thoroughly before selling them to control salmonella contamination. Because washing eggs is believed to damage the protective film of eggs, American supermarkets require eggs to be stored in cold storage. To prevent damage to the protective film on the surface of eggs, the European Union prohibits farms in member States from washing eggs. Because the protective film is well preserved, eggs in supermarkets in European countries can also be preserved at room temperature. Some eggs sold on the market in our country have been cleaned, some have not been cleaned, and the risk of contamination by pathogenic microorganisms may exist in the production of eggs. Therefore, eggs in the purchase of the fresher the better to eat, preservation according to the treatment of different room temperature generally can be stored for about 20 days, in 2 to 7 ℃ refrigeration conditions, the shelf life can reach 40 days or so.