Washoku apprentice / Top cooking tips for rehydration

The Yomiuri Shimbun

Deep-fried, simmered koyadofu and simmered shiitake

The Yomiuri ShimbunThis series presents basic information and tips for preparing washoku dishes. In this installment, we discuss how to rehydrate dried food.

When it comes to dried ingredients such as seaweed, mushrooms and other vegetables, many people struggle to finish a whole pack because they have run out of ideas for ways to use them. However, Satoru Nonaka, a teacher of Japanese cuisine at Ecole Tsuji Tokyo, recommends persistence. “Dried foods are convenient because they are rich in nutrients and keep longer,” he said.

Dried foods should be rehydrated before being seasoned. While many dried products — such as shiitake mushrooms, shredded daikon radish and hijiki seaweed — are rehydrated in water at or below room temperature, hot water is best for some. Regardless of water temperature, you should always use a drop-lid during rehydration. If you don’t, the ingredients left floating on the surface will likely absorb less water and end up with a texture different from the rest of the batch.

Slide 1 of 1

  • The Yomiuri Shimbun

Nonaka first demonstrated how to rehydrate dried shiitake mushrooms: “Water used to rehydrate the mushrooms can be reused for a dashi broth, so leave them in water for longer to extract some of their umami flavor,” he said.

First, immerse dried shiitake in plenty of water for about 30 minutes. Next, remove residue from the surface, remove the water, add some fresh water — just enough to submerge the ingredients — and leave for five to six hours until soft.

Nonaka then simmered the shiitake using the water used to rehydrate them. When the mushrooms are cooked, let them cool in the broth.

Koyadofu freeze-dried tofu is one of the dried foods that should be rehydrated in hot water because otherwise the center will remain hard, according to Nonaka.

Rehydrating it in boiling water will make it lose its shape or become cracked. Use boiling water that has been cooled to about 80 C, and pour it over a block of koyadofu (photo 1). Leave it for five minutes, then turn it over, and lave it for another five minutes. The hydrated koyadofu will be about 50 percent larger.

Pour water in a bowl and wash the koyadofu by gently pressing down on it until there is no longer a cloudy discharge (photo 2). Thoroughly washing it helps to reduce its odor.

Nonaka then deep-fried the koyadofu before simmering it. Deep-frying gives it a richer flavor and also prevents it from losing its shape, according to Nonaka.

Recipes for dried foods

Deep-fried, simmered koyadofu

Ingredients (serves 2):

1 piece of koyadofu freeze-dried tofu (7 by 5 centimeters)

Cooking oil

400 cc dashi broth prepared with bonito flakes and kombu

20 cc mirin

1 tbsp sugar

25 cc light soy sauce


1. Rehydrate koyadofu in hot water. Squeeze out excess water and cut into six pieces.

2. Deep-fry at 165 C until the surface becomes firm. Pour hot water over the pieces to remove excess oil. Remove excess water with kitchen paper.

3. Put dashi, mirin, sugar and light soy sauce in a pot. When the mixture comes to a boil, add the koyadofu and simmer the pieces over low heat for 15 minutes.

Simmered shiitake

Ingredients (serves 2):

2 dried shiitake mushrooms

50 cc dashi broth prepared with bonito flakes and kombu

50 cc water to rehydrate the shiitake

¼ tsp mirin

½ tsp sugar

1 tsp dark soy sauce


1. Rehydrate the dried shiitake in water and then remove the stems. Put the mushrooms, dashi and water used to rehydrate the mushrooms in a pot and simmer the ingredients over high heat with a drop lid placed directly on top of the ingredients. When it comes to a boil, lower the heat and simmer for 10 minutes.

2. Add mirin and sugar. Simmer until the liquid is reduced by half. Add dark soy sauce and simmer for another five minutes. Remove the pot from the heat and leave to cool.

* * *

To serve, place the koyadofu, shiitake and boiled spinach on a dish. Pour over the liquid used to simmer the koyadofu. Garnish with strips of yuzu rind.

To find out more about Japan’s attractions, visit


Click to play


+ -

Generating speech. Please wait...

Become a Premium Member to use this service.

Become a Premium Member to use this service.

Offline error: please try again.