Why are eggs fragile?

Egg shell is a special structure, which resists external force, but not internal force, so it is difficult for ordinary people to crush eggs, but chickens are easy to break from the inside.

In the process of boiling eggs, eggs will expand when heated and contract when cooled. The expansion degree of liquid egg white is greater than that of solid eggshell, which will generate internal forces and destroy the structure of eggshell. In this way, cooked eggs are easier to break than raw eggs.

The reason why the egg is cooked is that the gas in the egg expands rapidly when heated, or the egg has cracks.

For the former case, it is necessary to cook with cold water and small fire; For the latter, you need to scald it with boiling water first to solidify some protein and stick cracks, just like poached eggs when cooking noodles.

There are many ways to eat eggs, such as boiling, steaming, frying and frying. As far as the absorption and digestibility of nutrients in eggs are concerned, boiled eggs are 100%, tender eggs are 98%, scrambled eggs are 97%, poached eggs are 92.5%, old eggs are 8 1. 1%, and raw eggs are 30-50%.

From this point of view, boiled eggs and steamed eggs are the best ways to eat. Pay attention to chew slowly when eating, otherwise it will affect absorption and digestion.

How to cook eggs

1, soak in water. Before boiling eggs, it is best to soak them in cold water for a while, and then cook them in cold water, so that the eggshells are not easy to break. Of course, this is just one of the ways to keep the egg intact.

2. firepower. If fire is used when cooking eggs, it is easy to cause the air in the eggshell to expand rapidly, leading to the eggshell breaking; If you use a small fire, it will prolong the time of boiling eggs, and it is not easy to grasp the tenderness of eggs. Practice has proved that medium fire is most suitable for boiling eggs.

3. Time. After determining the firepower, as long as the cooking time is accurately mastered, the degree of tenderness of the eggs can be controlled at will. For example, boil soft eggs for 3 minutes. At this time, the egg white has solidified and the yolk is still fluid; Boiled eggs are boiled for 5 minutes. At this time, the egg white is solidified and the yolk is thick, soft and smooth; Boil hard eggs for 7 minutes. At this time, the egg white is solidified and the yolk is dry. It should be noted that you must not arbitrarily extend the time when cooking hard eggs. Because the egg is boiled in boiling water for too long, when it exceeds 10 minute, a series of chemical changes will occur inside the egg, thus reducing the nutritional value of the egg.

4. stir. In order to solidify the yolk in the middle of the egg white, the egg should be stirred in the same direction with a spoon after being put into the pot, so that the water in the pot turns in a vortex shape until it is cooked. As for what this principle is, it must be related to centrifugal force and centripetal force in physics.

5. How to peel: First, cool the boiled water in advance. Put the freshly boiled eggs in. Second, put some salt in the water when boiling eggs.