Photo/IllutrationPHOTO 1: Boiling time is (from right) six minutes, eight minutes and 13 minutes. (Photo by Masahiro Gohda)

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Editor’s note: The theme of Gohan Lab is to help people make simple, tasty "gohan" (meals). From the viewpoint of the science of cooking, we will explore recipes that will improve the cooking skills of beginners and offer discoveries by seasoned cooks. We will introduce the basics and arranged versions and explain the reasons behind the cooking process in the Cookery Science section.

The first installment is one of three on egg dishes. The “boiled egg” will be examined carefully this week.

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Should egg white have a shine to it? Should the yolk be moist or slightly runny? For anyone who tries their hand at cooking, boiling an egg seems to be the basic first step. If it turns out as one desires, a boiled egg is an impressive fare.

Since the protein of the egg sets gradually when heated, time is the key. An experiment was carried out by placing eggs in boiled water. The numbers above the eggs show how long they were boiled (PHOTO 1).

After six minutes, the egg white is softly set, but the yolk is slightly runny. It would be good to apply a drop of soy sauce and pop the egg into your mouth or place it on curry rice. The eight-minute egg is an all-arounder whose firmness is just right and it can be sliced for use in a salad. The 13-minute egg is hard boiled and when mixed with chopped onion and mayonnaise, you get a homemade tartar sauce.

If you are worried about the eggshell cracking, make a tiny hole before boiling to create an air passage. If the egg is cooled right after being boiled, the egg white shrinks, making it easier to peel. It is exhilarating when the eggshell peels in one go.

As the conditions change depending on the egg and the pot used, please look for those that suit you best.


(Supervised by Akiko Watanabe in the cooking aspect and Midori Kasai in the cookery science aspect)

* Ingredients and cooking utensils

2 eggs, salt, pot, bowl, ladle, spoon, pushpin, timer

1. To reduce the chance of the eggs cracking while being boiled, first take them out from fridge and leave at room temperature so there is less difference with the hot water temperature. Open a small hole in the middle of the less pointy end of shell (PHOTO A).

2. Pour water in pot enough to cover eggs, place over heat and add salt (1 to 2 tsp per 1 liter of water). This will help set the egg white in case it oozes out. When water comes to a boil, lower heat and carefully place eggs preferably using ladle (PHOTO B).

3. Set timer to desired firmness. The rough indication is: half-boiled with somewhat runny yolk in six minutes; center of yolk is soft in eight minutes; both egg white and yolk are firm in 13 minutes.

4. Have cold water ready in bowl. When time is up, remove eggs immediately and cool. If water turns warm, replace with cold water. When peeling, lightly hit with the backside of a large spoon and create fine cracks overall (PHOTO C). Peel under water.

5. When cutting in half, kitchen knife maybe used. But the cut surface turns out cleaner if a piece of thread goes around the middle of the egg, the ends crossed above the egg and pulled apart.

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Akiko Watanabe is a cooking expert specializing in Japanese cuisine.

Midori Kasai is a professor at Ochanomizu University and chairperson of the Japan Society of Cookery Science.


<Seasoned boiled egg>

It is easy to make seasoned eggs that will raise a bowl of ramen to that of store level. Boiled egg of any firmness may be used. Peel two boiled eggs. Place 2 Tbsp soy sauce, 2 tsp sweet mirin sake (or 1 tsp sugar), 4 Tbsp water in plastic bag and add eggs. Close bag so seasoning spreads. Eggs may be eaten after more than an hour.


An egg is structured such that the shell and membrane cover the egg white that covers the yolk. Although the egg white has a pH of around 7.5 right after it is laid, the pH rises to around 9 after the dissolved carbon dioxide flows out through the shell. The membrane and the egg white’s protein become less likely to stick to each other when the pH rises. To easily peel an egg, it is best to leave it in the fridge for about 10 days.

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From The Asahi Shimbun’s Gohan Lab column