Crackin' good

Cooking eggs might seem like the easiest thing in the world, yet sometimes they come out overcooked, undercooked, hard to peel, or with a green ring around the yolk. Here are some tips that will help you make perfect hard-cooked, soft-cooked or poached eggs every time.

Easy does it

Most egg-based recipes, such as custard sauce, give best results when cooked over low heat, and the same thing applies to hard- and soft-cooked, poached and scrambled eggs. There’s a good reason: the proteins in the egg white start to coagulate at around 65°C (150°F), while those in the yolk begin solidifying at around 70°C (158°F). That’s well below the temperature of boiling water (100°C or 212°F at sea level), which explains why eggs are easy to overcook—giving them rubbery whites and dry, chalky and greenish yolks. Even the flavour is affected: an overcooked egg smells more strongly of sulphur (that’s the unpleasant odour sometimes associated with egg sandwiches), which comes from the hydrogen sulfide given off by the whites during the coagulation process. For best results when boiling and poaching eggs, avoid a full boil; instead, use barely simmering water.

Storing eggs

  • Raw eggs in their shells keep for 35 to 40 days after laying. Heed the best-before date printed on the carton or on the egg itself.
  • Store eggs in the refrigerator as far as possible from strong-smelling foods, since eggshells are porous and can allow the egg to absorb odours. Keep the eggs in their carton, not in the egg compartment in the refrigerator door.
  • Separated whites can be refrigerated for 4 to 5 days in an airtight container. Separated  yolks are good for 2 to 3 days. For longer storage, you can freeze the whites.
  • Hard-cooked and poached eggs can be stored in the refrigerator for up to 3 days.

Eggs cooked in the shell

Avoiding the green

The grey-green ring that often appears on the surface of the yolk is caused by a chemical reaction between iron in the yolk and sulfur released from the white during the coagulation process. The reaction occurs much more easily in older eggs and in eggs that are overcooked. That’s why it’s important to cook eggs only as long as necessary and to stop cooking quickly by plunging them into cold water.

Centering the yolk

A hard-cooked egg is more attractive and easier to stuff if the yolk is well centered and surrounded with a reasonable amount of white on all sides. For perfect devilled eggs, make sure the eggs aren’t too close to their best-before date. As they age, eggs lose water through microscopic pores in the shell and the air space located at the wide end of the egg expands. Once cooked, an older egg, rather than being perfectly oval, is flat-bottomed, with only a thin layer of white remaining to hold the filling.

In addition to using a relatively fresh egg, there are other tips that can help you keep the yolk centered. The most common is to constantly roll the egg during the first few minutes of cooking. While this does work, it’s not very practical if you’re cooking a dozen eggs. Research has also shown that egg yolks may stay somewhat more centered if eggs are stored in a carton turned on its side rather than usual upright position. This isn’t a completely reliable method, but it’s worth a try.

These two eggs show the effect of freshness and proper cooking on the appearance of hard-cooked eggs. The egg on the right is four weeks old—just short of its best-before date. It was cooked in boiling water for 15 minutes and left to cool at room temperature. The yolk’s green exterior is obvious. The egg on the left is fresher and was cooked using the recommended method.

Peeling with ease

Sometimes the membrane under the shell clings to the egg white despite all efforts to pull it away without damaging the white. Very fresh eggs are more difficult to peel than eggs that are a few days old, because the fresher the egg, the stronger the bond between the white and the membrane. If you need to prepare a large number of hard-cooked eggs, plan ahead: buy the eggs about a week in advance and store them in the refrigerator. To make them easier to peel, roll the cooked eggs gently on the counter to crack the shell all over. Holding the egg under running water, start peeling from the wide end (where the air space is located), and lift the membrane away from the white.

Eggs cooked in the shell

This cooking method starts not with boiling water but with cold water, which helps prevent the shells from cracking due to thermal shock. The indicated times are for large eggs taken straight from the refrigerator.

  • Place the eggs in a saucepan in a single layer and add cold water, covering by at least 5 cm (2 inches).
  • Over high heat, bring to a rolling boil.
  • For soft-cooked eggs, remove the eggs as soon as the water boils. Serve immediately.
  • For hard-cooked eggs, cover the saucepan and remove it from the heat. Let rest for 10 to 12 minutes. Remove the eggs from the hot water and transfer to cold water to stop cooking, prevent the outside of the yolk from turning green and ease peeling.

Poached eggs

Keeping the white intact

When poaching eggs, the most daunting problem is preventing the white from spreading into the poaching liquid. The key to making attractive oval-shaped poached eggs is to use the freshest eggs possible, since a fresh egg’s more gelatinous white will stay closer to the yolk. To check an egg’s freshness, break oneonto a plate:  you should see thick, gelatinous white close to the yolk and a small amount of liquid white that spreads across the plate. The amount of thin, liquid white is an indicator of the egg’s freshness. As an egg ages, the white becomes slightly more alkaline, causing the proteins to repel one another and making the white more fluid.

To ensure that the white coagulates and quickly tightens around the yolk, add a small amount of vinegar to the poaching liquid (acidity speeds coagulation). Contrary to popular belief, salt does not inhibit coagulation, so you can certainly add some to the poaching liquid for flavour. Another popular myth maintains that swirling the liquid around the egg preserves its oval shape. Perhaps, but my personal experience shows that the best-looking poached eggs are made in perfectly still liquid.

How to poach eggs

  • Put about 5 cm (2 inches) of water or other liquid (e.g. broth) in a saucepan. Add a splash of vinegar and some salt if desired. Bring to a boil and reduce the heat until the liquid is barely simmering.
  • Break a fresh egg into a small cup. Tip the cup so that the rim touches the liquid and slide the egg very slowly into the liquid. The liquid part of the white will spread around the thick white and can be discarded after cooking.
  • Cook for 3 to 4 minutes. The white should be firm and the yolk runny.
  • Remove the egg with a slotted spoon and drain on a paper towel.

Christina Blais

For Christina Blais, explaining food chemistry to the masses is as simple as making a good omelet. Holding a Bachelor and Master degree in Nutrition, she has been a part-time lecturer for over 30 years in the Department of Nutrition at the Université de Montréal, where she teaches food science courses. She has been sharing the fruits of her experience with Ricardo since 2001, during his daily show broadcast on ICI Radio-Canada Télé. And diehards can also read her Food Chemistry on our website. You can follow her on Facebook at @Encuisineavecchristinablais.