Everything about eggs is not a trivial matter

On the ordinary people’s table, the appearance rate of eggs is always very high. It is almost the food that people eat every day. Whether it is steamed, boiled, fried, fried, or fried, eggs can become delicious and nutritious dishes. However, there are various kinds of knowledge and information on the market about this “table star”. What kind of eggs are considered fresh? How to preserve eggs? Do eggs need to be washed? What is the nutritional composition of eggs? Will eating more eggs lead to increased cholesterol and arteriosclerosis?

Recently, Professor Tong Qigen from the School of Food Science and Engineering of Beijing University of Agriculture answered several questions about eggs.

5 ways to tell if eggs are fresh
1. Look, touch, listen, smell

Look: Observe the appearance, shape, color and cleanliness of the egg. Good-quality fresh eggs are clean, meticulous, and bright in color, with regular egg shapes, no cracks, soft skin, obvious stomata, and other bad appearance conditions; poor-quality eggshells are shiny, dark gray or dark black, with oily leaching, and some More or larger mold spots.

Touch: Fresh eggs are heavy in the hand, with a pressing feel, and slightly rough; the old eggs are light in weight and have a smooth surface.

Listen: Shake the egg gently by your ears. If there is noise in the egg or the material in the egg vibrates, it is a poor quality egg. Or put a few eggs in your hands and gently touch each other to hear the sound. If the sound is really fresh; if the sound resembles the sound of knocking tiles, it is a preserved egg or a rotten egg; if it is a “pop” sound, the egg must be cracked .

Sniffing: Use your mouth to breathe a bit of heat on the eggshell, and then use your nose to sniff the smell. Good quality fresh eggs have a slight quicklime smell, if inferior quality eggs have a peculiar smell.

2. The more dense egg whites, the fresher the eggs

Egg white is also called egg white. There are layers of egg white. A complete egg is divided into four layers from the outside to the inside. The first layer is thin protein, the second layer is thick protein (outer dense protein), the third layer is thin protein, and the fourth layer is fringe layer thick protein (inner dense protein). During the storage of eggs, the proportion of thick egg whites in newly laid eggs is about 60%, but as time goes by, thick egg whites turn into thin ones. Therefore, the amount of thick protein can represent the freshness of the egg.

3. Buying eggs in summer, it is not recommended to buy eggs more than 25 days after the production date

Normally, the eggs in the farmers’ market are the freshest, but nowadays, people rarely have the time and energy to go to the farmers’ market to buy eggs, and more often they go to the supermarket to buy packed eggs in boxes. Boxed eggs do not mean that the eggs are not fresh, but the circulation time is longer. Therefore, you must carefully check the production date when buying boxed eggs in the supermarket. If it is a hot summer and the egg production has exceeded 25 days, do not buy it. It is more recommended to buy eggs less than 15 days old. If the weather is cold and the eggs are always stored in the refrigerator, the eggs can still be eaten if they are not more than 35 days old. Of course, it is not recommended to buy eggs that are longer than the production date.

In addition, pay attention to checking the shelf life of boxed eggs. Eggs from different manufacturers have different shelf life. This can only be used as a reference. Buy less eggs or choose not to buy eggs that are about to expire. Brand and price are also important references, and the quality of eggs from big brands is relatively guaranteed.

4. The longer the storage time, the larger the air chamber and the less fresh the eggs

At the blunt end (big end) of the egg, the air sacs formed by the separation of the protein membrane and the eggshell membrane are called air cells. The air cell of the egg is only formed at the blunt end, mainly because the blunt end has more and larger pores than the tip eggshell. During the storage period of the egg, the moisture in the egg is lost from the stomata of the egg to the air, making the air chamber larger. The longer the egg is stored, the larger the air chamber, so the size of the air chamber and the freshness of the egg It is also one of the main indicators for evaluating the freshness of eggs.

5. Eggs with blood stains, feces and various stains on the surface of the eggshell, it is best not to buy

If there is too much blood or feces on the surface of the egg shell, it means that the egg is heavily contaminated. Bacteria may penetrate into the egg through the stomata on the surface of the egg. It is best not to buy such eggs.

“Eating only egg whites and not egg yolks” is not advisable
It is very popular in the market to “eat only the egg whites and not the yolk”, but I don’t know that this practice loses most of the nutrients in the eggs.

87% of the protein is water, while the water content in the yolk is only 50%, and the protein content is 15%, far exceeding the protein. In addition, vitamins and minerals such as calcium and phosphorus are basically in the yolk.

Many people worry about the fat and cholesterol in the egg yolk. In fact, the egg yolk contains lipids, not exactly fat in the usual sense. Because it includes not only cholesterol, but also lecithin. Lecithin in egg yolk is 4 times that of cholesterol, and lecithin is a beneficial component for cardiovascular and cerebrovascular health. Studies have also shown that the choline in lecithin can prevent Alzheimer’s disease.

So far, there is no direct evidence that eating eggs will definitely increase the probability of arteriosclerosis. Therefore, it is not advisable to blindly discard the egg yolk.

3 ways to store eggs safely
Although every family has a refrigerator, there are ways to store eggs safely.

1. It is not recommended to store eggs in airtight containers: because eggs are living organisms, they have to breathe and discharge waste. If they are kept in airtight, the flavor of the eggs will deteriorate.

2. Use a few and take a few to avoid “secondary pollution”: When using eggs, do not take the egg container out of the refrigerator, but take out the amount used directly from the refrigerator, and avoid taking it out of the refrigerator and putting it in again. In the meantime, this will make the preservation of the eggs difficult. Because after the egg is taken out of the refrigerator, small water droplets will condense on the surface, and the bacteria and microorganisms in these water droplets will enter the egg, shortening the shelf life of the egg.

3. The eggs should be placed upright with the big end up: When storing, it is best to put the eggs in the egg box board and pay attention to the big end up. The top of the big head is an air chamber. As the storage time increases, the thick egg white gradually decreases, and the egg yolk “goes up”. If the small head is facing upwards and there is no air chamber barrier, the egg yolk will easily stick directly to the egg skin, causing the shell egg to stick.

Scientifically wash eggs to prevent pollution and extend shelf life
Should I wash the eggs I bought? In fact, if the purchased eggs are not dirty, they do not need to be washed and then stored, because washing may shorten the shelf life of the eggs. If the eggs you bought are stained a lot, they must be washed before storage.

How is the cleaning method scientific?

First of all, the eggs must not be directly soaked in water when washing the eggs, otherwise it will easily cause pollution. The correct way is to first moisten the surface of the eggshell, then wipe off the dirt with a wet wipe, and finally rinse it off.

Secondly, the temperature of the water for washing the eggs is better than the temperature of the eggs, that is, use water with a temperature between 36 and 38°C. This is done taking into account that the egg has stomata, and the water whose water temperature is higher than the egg temperature cannot easily enter the egg through the stomata.

Finally, the cleaned eggs should be scalded with hot water at 90 to 95°C for 2 to 3 seconds, and then dry the surface before storing. After this treatment, the shelf life of the eggs will not be reduced, but will increase.