This stuff on eggs is really dirty, be careful of "diseases from eating"

Audit expert: Jiang Tao

Vice Chairman of the Science Popularization Committee of the Chinese Society of Bioengineering

Eggs, as the most common source of food protein in our daily life, are affordable, nutritious and delicious. They can be steamed, fried, boiled and deep-fried. They are a well-deserved "all-purpose" ingredient.

Source: Beijing Youth Daily

However, when buying eggs, have you ever noticed that the surface of the eggs is not always so clean . Sometimes there are chicken feathers stuck on them, and sometimes there are some gray and white stains - chicken manure.

Source | Baidu

The surface of the egg is indeed a bit dirty

If you want to know why dirt appears on the surface of eggs, you must first understand the physiological structure of the hen.

Source: Zhihu

Hens lay eggs and defecate through the same part, called the "cloaca". This means that during the egg-laying process, the surface of the egg is likely to come into contact with feces and other dirt in the hen's body , making the eggshell look dirty.

In order to ensure quality, most egg factories will conduct preliminary screening , remove and discard eggs with dirtier surfaces, and only retain relatively clean eggs.

Some egg factories will also take further cleaning measures to provide comprehensive "cleaning care" for the eggs: first use warm water to do a "SPA" for the eggs for gentle cleansing, then blow dry and use ultraviolet rays to deeply clean and disinfect the eggs.

Source | Phoenix.com

After completing these cleaning steps, the egg factory will apply a special "body lotion" on the surface of the eggs. This "body lotion" is actually a layer of plastic wrap , which replaces the natural protective layer that has been washed away, effectively preventing external microorganisms from invading the eggs through the pores, thereby extending the shelf life of the eggs.

It’s important to note that while these cleaning steps can make the surface of the eggs appear cleaner, they cannot completely eliminate any microorganisms or viruses that may be present on the eggs.

As long as the surface of the eggshell is clean, is there any problem?

During the production, transportation and storage process, eggs are also easily contaminated by various pathogenic bacteria, among which the most well-known is Salmonella .

Source: Sogou

For eggs that are clean and relatively lightly contaminated, it takes time for microorganisms to gradually infect the inside. Specifically, at 25°C, it usually takes three days for Salmonella to penetrate the eggshell and shell membrane and infect the contents of the egg .

However, for those eggs with heavier surface contamination, microorganisms will multiply rapidly and invade the interior of the eggs in a relatively short period of time .

Source: Lightning News

According to data monitored by the Institute of Infectious Disease Prevention and Control of the Chinese Center for Disease Control and Prevention, Salmonella accounts for a very high proportion of foodborne disease incidents caused by bacteria , approximately between 60% and 80% .

After infection with Salmonella, there will be an incubation period of 6 to 24 hours without obvious symptoms . Once symptoms appear, they usually manifest clinically as gastroenteritis, and specific symptoms may include bloody stools, vomiting and fever .

Source | Baidu

It is worth noting that about 5% of infected people will develop more serious invasive symptoms , such as bacteremia and meningitis. Therefore, we should remain highly vigilant against Salmonella infection and seek medical treatment in a timely manner.

In addition, Staphylococcus aureus, Escherichia coli, and the more deadly Listeria monocytogenes may appear on eggs.

So, how can we eat eggs cleanly?

How can we avoid the risk of bacterial infection? Here is a hygienic guide for egg storage and cooking.

1. Cleaning before storage and preparation before cooking

It is not recommended to wash eggs before storing them in the refrigerator . Washing will destroy the natural film on the surface of the eggshell, which helps to prevent the invasion of foreign bacteria. Moreover, when washing, water may enter the egg through the tiny pores in the eggshell, providing an entry point for pathogens.

But before cooking , it is very important to make sure the surface of the eggs is clean. You can rinse the eggs under running water for more than 20 seconds to remove surface dirt and impurities.

Source | Sina

2. Storage tips in the refrigerator

When putting eggs in the refrigerator, it is recommended to store them separately from other foods , especially away from foods that are eaten directly, so as to avoid the bacteria that the eggs may carry contaminating other foods.

At the same time, it is recommended to place the eggs with the big end facing up . Because the air chamber prepared for the unhatched chicks to breathe is at the big end of the egg, and because of this, the big end has more pores, so placing the eggs with the big end facing up can make full use of the isolation characteristics of the air chamber, which is more effective in preventing microbial contamination. In addition, this placement method will not involve the movement of the yolk, thereby reducing the yolk sticking to the eggshell.

Source | Jianshu

3. Handling damaged eggs

Salmonella often attaches to eggshells. If the egg is cracked or broken , the egg liquid is likely to be contaminated with this bacteria. For safety reasons, damaged eggs should be discarded immediately and not eaten.

Source: NetEase

4. Cook until done

Salmonella is sensitive to high temperatures, but has strong survival ability in low temperature environments and can even survive in the refrigerator for 3 to 4 months .

Therefore, to ensure food safety, whether boiling, frying or cooking in other ways, you should ensure that the eggs reach a high enough temperature to kill salmonella. At 100°C, salmonella will die immediately; boiling at 70°C for 5 minutes, 65°C for 15-20 minutes or 60°C for 1 hour can also effectively kill this bacteria .

Source | Sohu

However, we don't have to worry too much. As long as the correct storage and cooking methods are adopted, the risk of bacterial infection will be greatly reduced. Let us maintain a scientific attitude while tasting the delicious taste of eggs, eat them reasonably, and enjoy them to your heart's content!