"It is difficult to peel boiled eggs made with fresh eggs." This fact has gradually become known to everyone recently. However, there seems to be some misunderstanding about "the reason why fresh eggs are difficult to peel."
We receive feedback from customers from time to time that the eggs stick to the eggshells and are in a very unfresh state
The reason why it is difficult to peel: In fact, it is too fresh!
Many people think that the eggshell is difficult to peel because the egg is not fresh, but the truth is just the opposite! Fresh eggs are more difficult to peel because the egg white contains more carbon dioxide, which is the culprit that makes the egg difficult to peel.
The subtle relationship between carbon dioxide and egg white
Fresh eggs have rich carbon dioxide in the egg white.
When the egg is heated and cooked, the carbon dioxide will expand due to the high temperature, making the egg white close to the membrane inside the eggshell.
This close combination makes it easy to tear the egg white when peeling, which makes people feel flustered.
Therefore, the fresher the egg, the more difficult it is to peel!
Boiled eggs are difficult to peel "only half of the egg white is left after peeling"?
Eggs that not so fresh are easier to peel
Are fresh eggs really harder to peel? Let's find out.
Fresh eggs contain a lot of carbon dioxide in the egg white, so it is generally said that "the carbon dioxide in the egg expands after boiling, pushing the egg white into the eggshell, making the egg white tightly attached to the eggshell, making it difficult to peel."
But in fact, whether the eggshell of a boiled egg is easy to peel depends mainly on the strength of the adhesion between the egg white and the membrane inside the shell (eggshell membrane), and the pH value (pH) affects the adhesion strength of the two.
The pH value of egg white in fresh eggs is about 7.6, which makes the heated egg white and the eggshell membrane fit tightly. If the egg white is left for a long time, the pH value will gradually increase, up to about 9.2 (the saltiness becomes stronger), so the connection between the eggshell membrane and the heated egg white will weaken, making it easier to peel.
How long should eggs be left for them to be easy to peel?
But how long should eggs be left for them to become easy to peel? According to research results, it is about a week. There are even research reports abroad that "5 days at 4 ℃, 3 days at 24 ℃, and 1 day at 38 ℃". Generally speaking, eggs are sent to retail stores for sale within two to three days after they are laid. Eggs bought from the store and kept at room temperature for two days, or refrigerated for about four days, are the easiest to peel when used for boiled eggs.
Some people sometimes say that "eggs in the past were easier to peel", and this is the reason. Nowadays, most eggs are bought from supermarkets and sold in freezers. They are refrigerated from shipment to store sales, while they were kept at room temperature in the past. At that time, when ordinary families boiled eggs, they usually used eggs that had been kept at room temperature for about three days from collection to purchase, so of course they were easy to peel.
Solution: Give the eggs some time!
If you want a boiled egg that is easy to peel and perfect, fresh eggs are not the best choice.
Here are some practical solutions:
Leave the eggs for 2-3 days
During this period, the carbon dioxide content in the eggs will decrease, and the tightness between the egg white and the inner membrane of the eggshell will decrease, making it easier to peel the shell.
Refrigerated storage: Reduce the impact of humidity
Storing the eggs in the refrigerator for a few days can also keep the eggs fresh.
Tips for boiling eggs
After boiling the eggs, put the eggs in ice water to cool them immediately. This helps separate the inner membrane from the egg white, making it easier to peel the shell.
Add a pinch of salt or a little vinegar to the water for better results.
How to tell if an egg is really not fresh?
Although eggs that are difficult to peel are usually because they are too fresh, there are also tips to tell whether the eggs are really not fresh:
Floating method
Put the eggs in water, fresh eggs will lie flat on the bottom of the water, and stale eggs will float.
Odor check
After opening the egg, if you smell a strange smell, it means that the egg has gone bad, so do not eat it.
Conclusion: Hard to peel is not a problem, knowing how to wait makes it perfect
Next time you find that a boiled egg is hard to peel, don’t be angry or doubt the freshness of the egg. Instead, be thankful because it may be a "newly-born egg"! Give it a little more time, and when the carbon dioxide content drops, you can easily peel a smooth and perfect boiled egg!
Further reading
K Kwong explains how to easily peel eggs
3-minute science: cracking the eggshell
1. The eggshell actually has 3 layers that wrap the egg white: A eggshell (calcium carbonate), B layer that sticks to the eggshell membrane, and C layer that wraps the egg white membrane.
2. When the egg is heated, B and C will become tougher and shrink at the same time. But B basically sticks to A after being heated. And C will also stick to the egg white after being heated. So when you crack C, you will also crack a little bit of egg white meat => oh my god!
3. Some people say that the freshness of the eggs will affect the ease of peeling. But how do you know how fresh the eggs are when you buy them?
4. Some people say that using a needle to poke a hole in the eggshell will make it easier to peel. In fact, this method only makes the eggshell less likely to burst when boiling the egg in boiling water, and has nothing to do with peeling.
5. Some people say that adding some vinegar and waiting for the eggshell to react with the vinegar to make the shell thinner will make it easier to peel (in fact, you really need to add a lot of vinegar first).
6. No matter how fresh it is, whether it is a hot spring egg, a runny egg or a boiled egg, Kzi uses cold water to rinse the egg and then freezes it with ice water to ensure that the egg white is not so sticky.
7. After freezing, use the back of a knife to knock the eggshell until it cracks, and then just push it open with your hands. You can also run water under the tap and push it all the way, so that the egg will be chewy when it comes out!
Peeling a cooked egg
References
- Why are my fresh eggs so hard to peel?
- The real reason why boiled eggs are hard to peel! Fresh ≠ easy to peel, break the myth and make it easy to peel (Chinese)
- Is the shell of a "boiled egg" sticky because the egg is not fresh? (Chinese)
- Boiled egg shells are hard to peel! The reason is that they are too fresh? Teach you a trick to peel the shell (Chinese)
