Learn the science behind:
Bacon and eggs for breakfast, a classic. On a lazy Sunday morning you’ll talk your time to make some. Grab some eggs and slice some bacon. You pre-heat the skillet while doing so and once it’s nice and warm you start frying those strips of bacon. The smell that comes off is amazing of course and makes you even more hungry. When the bacon is approaching doneness you break those eggs and drop them on the skillet. The whites quickly turn white and before overcooking the yolk, you want to take it from the pan again. But, it’s stuck. Super stuck and cannot be moved in any way. When trying to loosen it all you do is break the beautiful fried eggs.
Gone is the beautiful breakfast. The bacon still tastes good, but those eggs, it’s such a shame. But we’ve got some good news for you, there’s quite a simple trick for you to loosen those eggs again!
What happens when frying an egg?
Frying an egg in a pan will transform the way the egg looks. The egg starts liquid, with a translucent egg ‘white’ and shiny egg yolk. The white solidifies and actually turns white. The yolk will also solidify but will only change colour slightly and lose its shininess.
Most of this transformation is due to the egg proteins. An egg’s main ingredient (after water) is protein. These egg proteins are sensitive to heat. When they’re heated sufficiently they will unfold themselves (read more about protein theory). This is called denaturation and as a result they will coagulate. During this process they will start holding onto moisture and become intertwined, resulting in a solid egg. Egg white proteins undergo this transformation at a lower temperature than egg yolks. This is part of the reason that the egg white cooks faster than the yolk. The other reason is that the egg yolk simply lies further away from the heat. It just takes longer for the yolk to heat up to the required temperature.
Apart from the denaturation of these proteins some moisture will evaporate. Also, if the heat is high enough, the bottom of the egg will turn a light brown due to the Maillard reaction.
Why do fries eggs stick to your cast-iron pan?
There are a lot of theories online as to why your eggs stick to the pan. However, it is almost shocking to see that there doesn’t seem to be any proper research on the topic. There’s plenty of research how (egg) proteins react with all sorts of complex metal complexes, but a simple question as to why an egg sticks to a pan does not seem to have as extensive research behind it. If you know a researcher, maybe give them a hint?
That said though, there are plenty of theories. Let’s walk through the most common ones.
Metal surfaces are rough
If you have a super smooth surface it is hard for anything to stick. Think super smooth floors or walls. These smooth surfaces are easy to clean and won’t have things stick to them that easily either. The same goes for frying pans. Cast iron pans aren’t super smooth, instead they have a lot of tiny crevices and roughness on the surface. Little bits of an egg can sit in these pores, it’s a physical process. It probably won’t sink in very deep, but it’s enough to prevent your egg from sliding over the surface smoothly.
If this is the main reason it will be worthwhile to limit stirring and moving of the egg. Also, once it’s cooked it shouldn’t stick anymore. By that time the proteins have solidified and they can’t ‘sink’ into the crevices anymore.
Eggs react with metals
Various sources mention that the proteins in eggs react with the metal in pans. This will cause them to stick. It is supposed to be a chemical reaction. Proteins do change while frying eggs. The proteins denature which causes the egg to solidify. It is well possible that these proteins also react in some way, but the mechanism in which they would do so isn’t really explained anywhere.
If this is indeed the case there wouldn’t be any way to solve your issue once the eggs are stuck. However, as we see later, there is a way to get fried eggs loose again from the (cast-iron) pan. Therefore, there’s some doubt as to how this would work.
Prepping them incorrectly
These two causes are pretty unrelated to how the eggs themselves are made. When browsing online though there is a lot of advice that people are giving to prevent your eggs from sticking:
- Use plenty fat: that will indeed help the eggs from sticking to uneven surfaces since the oil already covers these up
- Use a super smooth pan: this works in plenty of cases, it’s the reason for the existence of non-stick pans, but remember, we’re using cast iron here which is almost never completely smooth
- Pre-heat the pan properly: everyone seems to have their own method, some use a low heat, others a medium and again others a high heat. There’s definitely a difference in how these eggs turn out, but there doesn’t seem to be a lot of consistency with regards to sticking here.
- Use the right kind of fat: some preach the use of coconut oil, others only bake with olive oil, no idea why one would work better than the other though…
- The temperature of the egg: some claim that a cold or too warm egg won’t work. could this really be of influence? If so, why? The pan should be a lot hotter than your egg, those few degrees shouldn’t matter.
The temperature of the pan
Some claim the temperature of the pan is important to prevent your eggs from sticking. However, the heat of your pan does a lot more than prevent or not prevent the sicking of the fried egg. The temperature also defines how well cooked the white and yolk are and how well balanced their ‘cook’ is. It’s therefore too simple to say that you should only bake an egg at a very low or high temperature. The egg might simply not turn out the way you like it. So before we can decide how best to control the temperature to prevent sticking, we have to discuss the overall impact of pan temperature on your eggs.
Impact of skillet temperature
When frying an egg the main thing you’d want to happen is that the proteins should solidify. However, depending on your taste you might not want all of them to do so. You might prefer a runny liquid yolk instead of a completely solid and drier one. Also, you might want your whites to be slightly soft, or turn a little hard. Frying an egg is actually quite a balancing act, there being two main routes to distinguish:
Hot & fast vs Cold & slow
In comes the ever returning interaction between temperature and time for cooking: hot & fast vs. cold & slow. If your temperature is high any cooking process will proceed fast, whereas at a lot temperature it will be a lot slower. Sometimes you’d like to make something at a high temperature, very fast (e.g. when using a wok or frying a steak). Hot and fast will help speed up (browning) reactions on the outside of your food, whereas the inside isn’t affected too much. In other instances though, you’d prefer cool and slow, think of a slow cooked beef or a cake. You don’t want a dark brown crispy cake crust with an undercooked inside, instead, you want an evenly cooked cake with a soft outside.
Both methods can be used when frying an egg. When frying your egg on a high heat the egg white cooks very fast. However, it will take some time for the yolk to heat through. In the meantime the egg white might already turn brown at the bottom. Use the hot and fast method when you prefer a slightly brown and crispy bottom but a still (slightly) runny egg.
However, if you’re frying at a low heat you won’t get any browning on the bottom, it’s not warm enough. Also, the proteins will set a lot slower. Because of this, the heat has more time to travel through the product before the bottom part of the egg has been fully cooked. As a result, the egg white and the yolk cook a lot more evenly and the overall egg will be a little softer and less crispy.
How to prevent sticking of fried eggs
Since temperature is already partially controlled by how you prefer your egg, you don’t have unlimited freedom to vary this to whatever you want to prevent sticking. Therefore, choose your temperature first when frying an egg. It’ wise to pre-heat your pan properly at this point, don’t add the eggs to the pan before even starting to heat. Instead, heat up the cast-iron to whichever heat you prefer.
Then, set to work in way that optimizes your chances for not making your egg stick:
- Coat the pan with some sort of fat, whichever you like. The most important thing is that a smooth surface is created which will help prevent the egg from sticking in all those little crevices.
- Add the eggs on top of the fat and leave it. By continuously moving it about you increase the chance for bits and pieces to still get stuck to the pan. Also, if there’s any interaction with the metal ions, you want to limit the number of proteins that get exposed to the surface and could possibly interact.
- Now, simply cook them until just before they are ready. Don’t worry if they are still stuck to the pan now, you did everything you could. This is where prevention didn’t help any further and you should switch over to solving your problem:
How to release fried eggs from the skillet
There is a trick to release most fried eggs from a hot cast-iron skillet and it has to do with temperature. When frying an egg both the egg and the skillet are super hot. As we know, at higher temperatures materials will expand slightly. A hot plate of steel will expand, even though you won’t see it. The same goes for the egg. The expansion of the egg is mostly due to moisture trapped inside which will expand. However, upon cooling the skillet and egg they’ll slightly detract again, especially the egg. This detraction can in a lot of cases loosen your egg from the pan without any issues.
So, next time your egg is stuck to your skillet, be patient, don’t panic. Turn off the heat, set the table, prep your other food and wait a few minutes. In this time the eggs won’t get cold, no worries, but they will detract just slightly. Removing the eggs will be as easy as pie!
Why it works? It might well be that the egg was stuck in some of those crevices, but by shrinking it came out again. It might have also reacted with the pan, but those bonds might have been less strong than internal bonds causing the egg to prefer to shrink into itself. Or it might be a completely different reason! About time someone does some more research on the topic!
A final note – The Leidenfrost effect?
While researching the topic of eggs sticking to a pan the Leidenfrost effect popped up. There might also be a relationship with this effect and the ease of sticking to a pan. Not sure exactly how though. That said, the Leidenfrost effect by itself is really cool.
The effect says that once your surface (e.g. a pan) is hot enough water will not evaporate anymore by splattering. Instead, it will roll around on the pan in small bubbles. See how this can help to prevent your eggs from sticking? If you add your eggs when the pan is hot enough, the moisture in the eggs might roll around the pan instead of stick to it. It will limit you to only using a hot pan, but if that’s the method you prefer anyway, give it a try!
We doubt some of the answers given to this question about sticking of eggs at the Kitchn, but if you’re desperate, have a look, your solution might just be there!
The theory behind the Leidenfrost effect by Jearl Walker.
What Einstein Told His Cook: Kitchen Science Explained, p 275, Robert Wolke, link
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