Pressure Cooking 101: Hard Boiled Eggs
Pressure cookers: they’re not just for dinner anymore! Cooking for Geeks gave the secret away: commercially hardboiled eggs are pressure cooked at 7.5 PSI. Pressure cooking eggs doesn’t save time, but it does provide very consistent results, with less active monitoring, and eliminates much of the potential for human error. Not only can you make hardboiled eggs in the pressure cooker, but they turn out exceptionally well (one of my taste testers remarked both how nicely they were cooked and how easy the eggs were to peel). This is a particularly useful method if you live at altitude, and have difficulty getting water to boil, or stay hot enough, long enough to cook your eggs properly – the pressure cooker cooks eggs at a higher temperature that you could otherwise attain. I also give you tips how to tell if older eggs are still safe to eat, how to prevent the grayish green ring around your yolks, and how to reduce the chances of eggs cracking during cooking.
Pressure cooking eggs doesn’t save a lot of time, but it is my preferred method. How many times have you been in the middle of making something in the kitchen when the phone or the doorbell rings, a pet, child or spouse distracts you, or something happens you need to deal with? I find that nothing will induce phone calls like a skillet with heating cooking oil or a tricky dish where I need to pay attention and time things. When I’m making breakfast (sausage, pancakes and eggs for example), I’m far more error prone when I’m still sleepy, and I’m far more likely to make a mistake if I have to juggle cooking several different dishes at once. I realized the other day that our kitchen timer has become really inaccurate. Its far too easy using conventional methods to either undercook or overcook your eggs. By using an electric pressure cooker to make hard boiled eggs, you can put them in the pot, set the timer, and ignore them until pressure is released. Because electric pressure cookers automatically turn off the pressure and change to “keep warm” setting, if you forget and let them go 5 minutes too long, pretty much the worst that’s going to happen is some discoloration around the yolk, but they’re still very edible. It’s a very forgiving method.
How Old Are My Eggs? How to Test if Eggs Are Still Good. The expiration date on your eggs is a very conservative guideline, and you can often safely eat refrigerated eggs for weeks or even a month after the expiration date on the package. But you should test them first, just to be safe. Egg shells are porous, and as eggs age, they lose moisture and carbon dioxide, their air sacs grow larger, and they become more buoyant. This test is also useful for baking, where for some applications, such as those where you want your eggs to have more volume (like meringue), or for cakes, fresh eggs are best, and in others, older eggs are better. If an egg has cracked while in the refrigerator, don’t test it, throw it out: egg shell cracks provide a big gaping hole for bacteria to enter the egg, and you don’t want to contaminate the water you’re going to test other eggs in. Trust me: I got a very mild case of salmonella in my early 20s from some slightly undercooked chicken, and it was the worst experience of my life. Eggs are plentiful and cheap, and while I’m all for frugality, its not worth saving cracked ones to risk 5 to 7 seven days of abject illness and misery, not to mention lost work.
You should perform this test immediately before using the eggs, and only test the number of eggs that you intend to use at that time: egg shells have a protective coating that helps prevent contamination, and that coating is lost when the eggs are “washed”. Pour some cold water into a tall container (I usually use a large, Big Gulp size drinking glass) and gently add an egg at a time, placing it carefully on the bottom. The water should be several inches over the top of the egg. If the eggs are fresh, they will lie on their side at the bottom. If they are older, but still safe to eat, one end of the egg may rise up (so that the egg is now vertical), but the egg will remain at the bottom. If the eggs are too old, they will rise and float to the surface of the water. Floaters are too old and unsafe to eat, and should be discarded.
What Causes the Green Discoloration Around Egg Yolks and How to Prevent It. The greenish gray color around cooked egg yolks is caused when eggs are overcooked, and when they are heated at high temperatures over a long period of time. When heated, sulfur in the white (the albumen) breaks off from proteins, and combines with hydrogen to create hydrogen sulfide. The hydrogen sulfide in turn moves towards the center of the egg, where it is cooler, and reacts with iron from the yolk to create ferrous sulfide, the gray green substance that rings egg yolks. Experimental Cookery explains that rapid cooling is key: “When the egg is placed in cold water immediately after cooking the lowering of the temperature at the surface of the egg lowers the pressure there. . .if the egg is placed immediately in cold water after cooking, the hydrogen sulfide diffuses to the surface of the egg. . .” (this may explain the small bubbles seen on the egg surface in the photo for Step 7 below) Older eggs may be particularly susceptible to this problem because egg whites become more alkaline as they age. On Food and Cooking says that “Yolk greening can be minimized by using fresh eggs, by cooking them as briefly as possible, and by cooling them rapidly after cooking.” I’ve made plenty of older hardboiled eggs without this problem, but as soon as pressure is released on your machine, remove the hard boiled eggs with tongs and immerse them in a bowl of cold water.
How to Reduce the Chances of Eggs Cracking While Cooking. Egg cracking is generally caused by either rapid changes in pressure, temperature, thin or aging egg shells, or a combination thereof. From my research, it seems that thin shells can be caused by a number of factors: very new or old laying hens (in the case of the latter, egg size increases as a hen ages, but the mass of the shell remains the same, hence, thinner shells), either an inadequate or an excessive amount of calcium in the chicken feed, the pore size of the eggs, or even the hot summer months, which apparently trigger calcium conservation in chickens. When you pressure cook eggs, you are essentially quickly cooking them in steam, not boiling them, so you don’t really have to worry about water getting into the shells, and cracks won’t matter anyway if you’re making egg salad, deviled eggs or potato salad, but you don’t want cracked eggs if you’re serving guests or making Easter eggs. If you find that your current brand tends to crack, try another. Or change from extra large to large eggs. You can also add a little vinegar to the cooking water to help prevent cracking (though some people can detect the taste of vinegar). Salt is also recommended, although I’ve already included it as part of the recipe below (for taste). Instead of putting eggs straight from the refrigerator into the pressure cooker, CookWise recommends placing the eggs in a bowl of hot water for 4 or 5 minutes, draining the water, adding more hot water, and letting them sit for another 5 minutes before cooking. This will help warm the eggs up to room temperature and reduce the chances of cracking.
Coarse kosher salt
1 cup of cold water
Extra large eggs
Electric pressure cooker
12″ silicone tipped tongs
Trivet or vegetable steamer
Large bowl full of cold water
EGG TIP: CookWise recommends warming eggs up before cooking to reduce the chances of cracking. Put the eggs in a bowl, fill it with hot tap water, let stand for 5 minutes, pour out the water, then repeat. Alternatively, you could pull the eggs out of the refrigerator a half hour before pressure cooking them.
- Add ½ teaspoon of coarse kosher salt and 1 cup of cold water to the pressure cooker bowl. If you have a jiggle top pressure cooker, you may want to add additional water.
- Add a trivet or vegetable steamer to the pressure cooker bowl.
- Tear off a few inches of tin foil. Loosely crumple the tin foil so it’s a long crumpled piece, then bend the ends so they touch and form a circle. You can twist the ends together, if you wish. Make enough of these tin foil rings for each of your eggs. Place the foil rings on top of the trivet or vegetable steamer. (You can recycle these when done, or as long as they stay clean, you can reuse them again.) If you have Heat Safe Egg Cups, you can use those instead.
- Examine each of your eggs, find the larger end, and place each egg, larger side on the bottom, into each of the foil rings. Adjust the rings and eggs as necessary to keep each egg standing upright and keep the eggs from touching one another.
- Pressure cook your extra large eggs at LOW PRESSURE (6 PSI) for 5 minutes using QUICK PRESSURE RELEASE for hardboiled eggs. If you have smaller eggs, I recommend you test a single egg first at 4 minutes, and adjust your timing up or down depending on how it comes out. If you want softboiled or medium eggs instead, I recommend you test eggs one at a time, reducing the time 1 minute each time, until you get the desired level of doneness.
- While your cooker is coming up to pressure, get out a larger container or bowl and fill it with cold water. You want a good amount of water so it stays cold when you add the eggs, instead of the hot eggs bringing the water’s temperature up. You can add a few ice cubes if you want to make it extra cold. When the pressure cooker timer goes off, turn off the “keep warm” function and use your tongs to move the pressure valve to “release”. (Those with stovetop pressure cookers should take their pot off the stove and run it under cold water to release pressure as quickly as possible.)
- When pressure is released, immediately remove the pressure cooker lid, holding it at an angle, with the back side up, so that any hot water in the lid falls back into the bowl. Using your tongs, remove each of the eggs and immediately place them in the large bowl of cold water. If you want to eat the eggs right away, let the eggs remain in the water until they have cooled enough that you can handle them comfortably. If not, leave them in the water until they have completely cooled.
COOKING TIP: Experimental Cookery says: “When an egg has been cooked in hot water for 15 minutes or longer a dark greenish color may be formed on the surface of the egg yolk.” Pressure cooking hardboiled eggs takes about that long, though during a good part of that time, the water is being heated, and is not yet hot. The author explains further: “The amount of hydrogen sulfide evolved depends on (1) the time of heating, (2) the temperature reached, and (3) the reaction of the egg.” In pressure cooking, the temperature reached is necessarily going to be higher, but On Food and Cooking confirms the answer to the first and third parts of the equation: “Yolk greening can be minimized by using fresh eggs, by cooking them as briefly as possible, and by cooling them rapidly after cooking.” Pressure cooking eggs already shortens the cooking time, and rapid cooling of the hard boiled eggs reduces the “heating” time even further (item 1), and as eggs age, their whites become more alkaline, providing a more conducive environment for sulfur to split off and migrate towards the yolk. Fresh eggs provide a less favorable environment for the formation of ferrous sulfide (item 3).
YOLKS TIP: If you are making deviled eggs or some other application where “centered” yolks and presentation are important, use fresh eggs, move them onto their sides in the refrigerator a few hours before cooking. (For that matter, you could also cook them on their sides, making sure the eggs are separated.)
- Coarse kosher salt
- 1 cup of cold water
- Extra large eggs
- Add 1 cup of cold water and ½ teaspoon of coarse kosher salt to the pressure cooker bowl. If you have a jiggle top pressure cooker, you may want to consult your owner's manual to see if you should add additional water.
- Place your trivet or vegetable steamer in the bowl.
- Cut a piece of tinfoil several inches wide. Loosely crumple the aluminum foil into a long snake, and move the two ends together to form a loose ring (you can twist them together, if you prefer). Place the rings on the trivet / vegetable steamer. You can re-use these foil egg stands as long as they remain clean. You can use Heatsafe Egg Cups instead, if you prefer.
- Place the larger end of each egg into a foil ring, adjusting the foil as needed to keep the egg upright and keep the eggs from touching one another.
- Pressure cook your eggs at LOW PRESSURE (6 PSI) for 5 minutes using QUICK PRESSURE RELEASE.
- Fill a large container or bowl with cold water (add ice, if you wish). (You want to use enough cold water that it cools the cooked eggs, rather than the cooked eggs warming up the water.) When the timer beeps, turn the unit off, and using the tongs to move the pressure valve to the "release" position. (Those with standardized stove top pressure cookers should remove their pots from the heat, and run them under cold water for the quickest pressure release.)
- When pressure is released, remove the lid, tilting it at an angle over the pot so any hot water drips down into the bowl. Use the tongs to immediately remove the eggs from the pressure cooker and move them into the cold water bath. If you plan to eat the eggs later on, you can leave them in the water bath until room temperature. If you wish to eat them right away, keep them in the water until they have cooled sufficiently that you can handle them.