World Egg Day | Four major problems of eating eggs, one article to help you solve →

World Egg Day was established in Vienna in 1996. It is held on the second Friday of October every year to celebrate the power of eggs - one egg provides more than a dozen essential vitamins and minerals, as well as high-quality protein.

Today is World Egg Day this year. We often eat eggs, but we also have difficulties eating eggs. Here are the four major problems we should solve when eating eggs.

Question 1 : Red skin or white skin? Which one is more nutritious?

The difference is not big. The color of the eggshell is related to the breed of chicken and has nothing to do with the nutritional value.

The color of the eggshell is mainly determined by the "protoporphyrin pigment" in the eggshell. The more protoporphyrin pigment there is, the darker the color of the eggshell. Protoporphyrin pigment itself has no nutritional value. The content and synthesis capacity of protoporphyrin pigment are mainly determined by genetic genes. In other words, the color of the eggshell depends on the type of hen and is "natural" and has nothing to do with human factors.

The nutrients in eggs mainly include protein, vitamins, fats and minerals. The nutritional differences between eggs of different colors are not big, so don't worry too much about their colors. Whether it is white eggs or red eggs, freshness and safety are the most important.

Problem 2: The annoying “shell-protecting” phenomenon, how to peel a beautiful egg?

When peeling a cooked egg, you will often see the egg white peeled off together, commonly known as "shell protection". This is mainly caused by the egg shell membrane and the egg white sticking together.

Eggs are eggs laid by chickens. The outermost layer is a hard eggshell, and there are two layers of shell membranes between the eggshell and the egg. The outer shell membrane is tightly attached to the eggshell, and the inner shell membrane is tightly attached to the egg white.

In fresh eggs, the two membranes are not easy to separate from each other, nor from the eggshell or egg white. After cooking, the inner shell membrane easily adheres to the cooked or coagulated egg white because the egg inner shell membrane has a relatively strong adhesion to the egg white.

To make eggs easier to peel, it is necessary to reduce the adhesion between the egg shell membrane and the egg white, which requires increasing the pH value of the environment inside the egg.

How to increase the pH value of eggs? Scientists have conducted several small experiments to explore the relationship between temperature and the ease of peeling eggs. Scientists placed eggs in 4℃, 24℃ and 38℃ environments respectively, and found that eggs placed in 38℃ environment are easiest to peel after being cooked, followed by eggs placed in 24℃ environment, and the slowest is placed in 4℃ environment. In other words, the higher the temperature of the environment where the eggs are placed, the faster the pH value of the eggs increases, and the easier it is to peel the eggs after they are cooked.

In order to make the fresh eggs easy to peel quickly, some egg processing factories place them in a warm and well-ventilated environment. However, at home, eggs are usually kept in the refrigerator to keep them fresh.

At the same time, the storage time can also affect the ease of peeling eggs. In different environments, the storage time required to make the egg shell easy to peel is also different. For example, in a 38°C environment, it is easier to peel eggs after being stored for 1 day, while in a 24°C environment, it takes 3 days, and in a 4°C environment, it takes 5 days. In other words, the longer the eggs are stored, the easier they will be to peel. Of course, the storage time cannot exceed the shelf life, otherwise, what is the point of easy peeling.

Question 3: After the egg is cooked, the surface of the yolk turns mysteriously “green”. Can it be eaten?

In fact, it is normal for egg yolks to turn green.

The reason why eggs turn green is that if they are boiled for a long time, methionine will release sulfide, which will react with the iron in the eggs to form dark-colored ferrous sulfide.

Green eggs do not have a big impact on the body, because the sulfide in the egg yolk is very small, which may turn into hydrogen sulfide and ferrous chloride under the action of stomach acid. If it does not react with stomach acid, it is also a water-insoluble compound and will not participate in the metabolic process.

Secondly, the digestive process of human intestines is microbial fermentation, and it is normal to produce metabolic wastes such as hydrogen sulfide and biogenic amines. The amount of hydrogen sulfide in the intestines far exceeds the water-insoluble ferrous sulfide on the egg yolk, so it is safe to eat.

Question 4: I heard that raw eggs are more nutritious. Can I eat them often?

Eating raw eggs is not only not nutritious, it may also be harmful to your health.

"Hairy eggs" are "dead eggs", which are embryos that have been incubated halfway through. During the incubation period, the nutrients in the eggs are converted into chicken nutrients. While retaining nutrients such as protein and fatty acids, vitamins and other ingredients are also consumed to a certain extent. This means that the nutritional value of hairy eggs is not higher than that of chicken eggs.

In addition, raw eggs may often contain parasites and pathogenic bacteria such as Salmonella, Escherichia coli, and Salmonella typhi, and it is difficult to ensure hygiene and safety. Eating them can easily cause digestive tract diseases. It is recommended that you eat less.

Source: Science Popularization China, China Science Popularization Expo, China Family Doctor Magazine, etc.