Tender Whites, Uniformly Opaque Yolks
Easy-to-Peel Shells for Smooth, Blemish-Free Whites
The test kitchen has a sure-fire method for producing perfect hard-cooked eggs: Put the eggs in a saucepan, cover them with an inch of cold water, bring the water to a boil, cover the pot, let the eggs sit off the heat in the cooling water for 10 minutes, and then transfer them to an ice bath for 5 minutes before peeling. You’ll get tender whites and uniformly opaque (but not chalky) yolks every time.
But eggs cooked this way can be difficult to peel—a problem that has more to do with the membrane that lines the shell than with the shell itself. When that membrane cements itself to the egg, it must be painstakingly peeled away and often takes pieces of the white with it, leaving an unappealingly pitted exterior—an unacceptable result when you need flawless eggs for deviled eggs or garnishing a salad.
The Impact of Age
“Fresh eggs are harder to peel than older eggs.” This piece of conventional wisdom seemed like the natural place to start my testing. Could the key to success really be as simple as choosing the proper eggs to cook?
Here’s the science behind the claim: The white in a fresh egg is slightly alkaline. As the egg ages, the white becomes more alkaline as the dissolved carbon dioxide (a weak acid) it contains dissipates—and the more alkaline the white, the easier it is to peel when cooked. Why? Because the higher alkalinity causes the egg white proteins to bond to each other, not to the membrane directly under the shell. That’s the theory, anyway.
To test it, I used our foolproof method to cook 18 fresh and 18 month-old eggs, peeling them all right after they’d cooled. As expected, many of the fresh eggs were difficult to peel, and a few were downright impossible. But the older eggs weren’t a guarantee for easy peeling either—some were actually quite difficult—so I moved on.
Having exhausted my options in terms of ingredients (there was only one), I moved on to the cooking method. Our foolproof approach makes it impossible to overcook the eggs, but if another method would make peeling easier, I was willing to branch out.
I compared five methods—our foolproof method, boiling in already-boiling water, steaming in a pressure cooker, steaming over boiling water, and baking—cooking 10 eggs each way and peeling them all right after cooling them in a 5-minute ice bath.
I graded each method from A to F: If most of the eggs cooked a certain way peeled easily, the method got an A. If the shell clung stubbornly to most of the eggs, forcing me to tear the whites, it received a lesser grade.
The foolproof and baking methods produced eggs that were challenging to peel; they each scored a C (but unlike the nicely cooked foolproof eggs, the baked ones sported green rings around their yolks). The pressure-cooked eggs were nicely cooked, and the method earned a B. But the steaming and boiling methods both earned an A. Their shells slipped off to reveal perfectly smooth whites. What made them (and the pressure-cooked eggs) succeed?
A Report Card on Peelability
We compared five methods, cooking 10 eggs per method and peeling them all after letting them cool for 5 minutes in an ice bath. We then assigned a grade to each method based on the condition of the peeled eggs. Our takeaway: The steaming and boiling methods both earned an A, as nine of the 10 peeled eggs cooked each way were flawlessly smooth.
Peeling Away the Answer
The only real common denominator of the boiled and steamed eggs was that both went directly into a hot environment, whereas eggs cooked by our foolproof method started out cold and warmed up slowly as the water came up to a boil. The baked eggs also qualified as using a cold start because the oven’s air is a slow and inefficient conductor of energy.
Our science editor explained what was happening: Plunging raw eggs into boiling water (or hot steam) rapidly denatures the outermost proteins of the white, which reduces their ability to bond with the membrane. Plus, those rapidly denaturing proteins shrink as they start to bond together, and that causes the white to pull away from the membrane. Thus, these eggs are easy to peel. (The pressure-cooked eggs are a unique case: Though they start out in cold water, the water gets hot very rapidly and can reach as high as 250 degrees, which likely causes additional shrinkage of the proteins, making the eggs easy to peel.) Conversely, proteins that rise in temperature slowly, as in the eggs started in cold water or baked in the oven, have more time to bond to the membrane before they bond with each other, so the membrane is difficult to remove.
Science: Blame the Membrane
Most cooks assume that when an egg is difficult to peel, it’s because the shell is sticking to the egg white. But it’s the membrane between the shell and the white that’s really the problem. When an egg is very fresh or when it’s cooked slowly, the proteins in the white bond to the membrane instead of to one another, and the membrane becomes cemented to the white and impossible to peel away. The solution: Plunging the eggs directly into hot steam, which causes the egg white proteins to denature and shrink, reducing their ability to bond with the membrane.
Full Steam Ahead
As for which hot-start method it would be—steaming or boiling—I had an idea. When I developed a recipe for Soft-Cooked Eggs, I determined that steaming was a superior method to boiling because adding eggs to a pot of boiling water lowers the temperature of the water, making it hard to nail down a precise cooking time that will give you dependable results every time. Eggs that steam in a steamer basket, on the other hand, don’t touch the water, which means they don’t lower the water temperature, so the same cooking time produces consistently perfect results. Plus, steaming is faster because there’s less water to bring to a boil.
To prove the point, I compared the two methods: I filled one saucepan with water, brought the water to a boil, carefully lowered six eggs into the water, covered the pot, and then turned down the heat slightly so the eggs wouldn’t jostle and break. In another saucepan, I brought 1 inch of water to a boil and then placed a steamer basket loaded with six eggs into it before covering the pot. After 13 minutes (which a few tests showed was ideal), I transferred all the eggs to an ice bath and chilled them for 15 minutes.
Sure enough, I preferred the texture of the steamed eggs. Their yolks were uniformly cooked but not chalky, while the yolks of the boiled eggs were just a tiny bit translucent at the center, just a bit undercooked—likely due to a temporary dip in temperature when the cold eggs went in.
Peel Six Eggs in 41 Seconds!
I had one last challenge: Would my steaming method make even notoriously difficult fresh eggs easy to peel? Indeed it did. I was able to peel six eggs in just over 2 minutes. (When I used a novel method of enclosing eggs in a plastic container with water and shaking them vigorously, I cut that time to mere seconds.)
I was so pleased that I decided to showcase the eggs’ beautifully smooth exteriors by making deviled eggs. The test kitchen already has a recipe for the classic version, so I created a few new approaches: curry, bacon-chive, and chipotle pepper with pickled radishes. Thanks to my new cooking method, throwing these together couldn’t have been easier.