The derisory comment "he can't even boil an egg" is sometimes used on people who can't cook. However, when it comes down to it, how many people can really make a good boiled egg? Julia Child's "The Way to Cook", a nationwide bestseller in the UK, devotes page 62 to how to boil the "perfect" egg. While its attention to fundamentals is noteworthy, it implicitly presupposes that there is only one "perfect" type of boiled egg - one with a hard white, and a firm yolk that is not overcooked.
The Japanese, with their onsen tamago and nitamago and even "inside-out" eggs (with the yolk wrapped around the white), have their own notions of what makes a good boiled egg. The art of making nitamago illustrates this. The objective is to achieve a firm, springy, evenly seasoned white, and slightly gooey, though not totally runny, yolk that is positioned nicely in the centre of the egg.
From a quick survey of the culinary literature, several things seem to be almost universally agreed upon. First, the egg should be fresh, but not too fresh. It's essentially a tradeoff. The firmer white in a fresh egg will be better able to "support" the yolk in the centre. However, fresh eggs (1-2 days old) are incredibly difficult to peel as the membrane beneath the shell sticks tightly to the shell. After a few days in the refrigerator the egg becomes easier to peel. However, as eggs age (more than 14 days or so in the fridge, depending on storage conditions), the egg yolk expands, the white thins, the air sac grows and the membrane weakens, and there is a corresponding deterioration in terms of flavour and texture.
Second, it is not necessary (and often counterproductive) to keep the water at a rolling boil since egg whites and yolks coagulate well below 100°C. Egg whites begin to thicken at about 60°C and solidify when the temperature reaches 65°C. The yolk protein will start to thicken at 65°C and will harden at 70°C. If eggs are cooked at boiling point for too long they will get rubbery and an unsightly (but harmless) greenish-grey film will develop over the yolks (due to the sulphides from decomposition of the amino acids in the white reacting with iron in the yolk; but you really didn't need to know that). Plunging the cooked eggs into cold water briefly can stop this film from forming.
Third is, to coin a broad phrase, saucepan technique. Most cooks recommend a tall saucepan that can accommodate all the eggs one wishes to boil in one layer, as piling eggs on top of each other will make cooking time vary too much. Water should cover the eggs by an inch or so, and the eggs should either lay on their sides or turn onto their tips (due to the air sac) but should not float - they are rotten if they do. Some advocate adding a pinch of salt or a spoonful of vinegar to the water, in order to "set" the white more quickly if a crack should develop in the shell and the white start to flow out. (On a related note, many cooks also recommend gently piercing the broad end of the egg with a pin prior to boiling, as this punctures the air sac and relieves the pressure on the shell that can cause it to crack if the egg is plunged into boiling water.) Lastly, to centre the yolk, some advocate turning the egg gently with a wooden spatula every 30 seconds or so that the egg is in the hot water.
Having gone on at length, the million-dollar question is "how long do I boil the eggs for"? Sadly, there is no one answer. Timings vary according to the starting temperature of the egg, the egg size, and the desired result, among other things. Here we will standardise some variables as follows: using eggs that weigh approximately 55g, taken directly from the fridge (i.e. about 4°C). We'll use lightly salted water covering the eggs with an inch to spare. We will try also for nitamago excellence - firm outer egg white which has soaked in the flavour of the marinade, a slightly jelly-like inner white layer, and deliciously gooey but not liquid yolk.
The cooking method will be as follows (there are of course different methods, so it's necessary to specify which one I've used): after testing the correct level of water, remove the eggs. Then, bring the water to a rolling boil. Place the eggs into the water with a slotted spoon or similar implement. Once the water returns to a boil, turn the heat down to a gentle, simmering boil, and begin timing without covering the saucepan. Once the target time is reached, remove the egg, and soak in ice water for a few minutes to halt the cooking process.
The verdict: it takes 6.5 minutes to produce the desired result using the given egg size and the corresponding conditions.
[To go a step further and make nitamago, peel and then soak the eggs in freezer bag containing a mixture of 100ml of water, 2 tbsp of soy sauce, 2 tbsp of mirin (Japanese sweet rice wine), a few slices of ginger, and 2 tbsp of sugar. (Vary the proportions according to taste.) Place the freezer bag in the fridge for about 3-9 hours (the longer the egg is soaked, the more intense the colour and flavouring).]
As a side note, yolk colour is sometimes used as an indication of egg quality; the more deeply-coloured the yolk, the happier and healthier the chicken. This is usually associated with chickens raised on open pasture and fed organic food (grains, worms, seeds etc). However, there is a caveat to this - commercial poultry feed often contains additives such as canthaxanthin that gives the yolks of eggs laid by battery hens a healthy-looking orange tint. According to the UK's Food Standards Agency, canthaxanthin (E161G) is a type of carotenoid. These substances are related to beta-carotene, the red/orange pigment present in carrots. The presence of canthaxanthin in poultry feed can lead to a more intensely-coloured yolk (it is also used in fish feed to give farmed salmon and trout richer-coloured flesh). Currently, the EU has established a limit of 80mg/kg of feed, though in practice the norm is 20mg/kg for poultry. There is some evidence that high intake of canthaxanthin can lead to deposition on the retina (not sure what this results in - yellow vision??), but this is not believed to be permanent. The point, I suppose, is that more intensely golden eggs don't always mean they are "better" or "healthier", unless one can be certain that the chickens are organically raised on feed with no chemical additives. Makes rearing chickens seem attractive.
