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Naturally Freeze-Dried! Japanese Traditional "Frozen Tofu"

Updated: Apr 26, 2022

Introducing noteworthy nutritional values and unique recipes!

Tofu has become so popular as a staple of healthy food, but have you ever heard of "Kori-Tofu," or frozen and dried tofu? Kori-Tofu is a traditional Japanese preserved food that has been eaten since olden times in the cold mountainous areas of the Tohoku region and Nagano Prefecture. Many people may be surprised at the idea of frozen tofu. If you have never tasted it before, you may be curious about what it tastes like. In this article, we will introduce the origins of Kori-Tofu prepared in the middle of winter, where it came from, how it is made, and some nutritional information and unique recipes. Table of Contents 1. Two origins of Kori-Tofu 2. The nutrients in Kori-Tofu 3. Recipes using store-bought Kori-Tofu 4. Recipes using homemade Kori-Tofu 5. Summary

1. Two origins of Kori-Tofu

↑ Koya Mountain in snow. In this cold weather, "Koya Tofu" was born. As the name suggests, "Kori(=Frozen in Japanese)-Tofu" is made by freezing tofu. There are two lineages of Kori-Tofu that can be traced back to its origins. The first is "Koya Tofu," which originated in Koya-san (Mt. Koya), a holy place of Japanese Buddhism in Wakayama Prefecture. The other is "Shimi(=Frozen in Japanese also)-Tofu," which originated in the cold rural areas of Shinshu and the Tohoku region. Although there are differences in the names of the different regions, the unified name "Kori-Tofu" is defined by the Japanese Agricultural Standards (JIS). We use "Kori-Tofu" as a proper term. There are many stories about the origin of frozen tofu, but for "Koya Tofu," the birthplace is believed to be Koya-san monastery, located in Koya-cho, northern Wakayama Prefecture. Koya-san monastery is a sacred place of Buddhism in Japan, founded by the famous Buddhist monk Kobo-Daishi Kukai, and was registered as a World Heritage Site in 2016. The story goes that a young monk at a temple in Koya-san inadvertently left tofu outdoors on a cold winter night, and when he ate the frozen tofu the next day, it was delicious. Legend has it that Kukai brought tofu-making techniques back to Japan from China, where he studied soybeans. It is said that when the monks who practiced Buddhism at Koya-san spread the teachings of Buddhism throughout Japan, Koya Tofu, a preserved food that is lightweight, easy to carry around, and highly nutritious, also spread throughout the country.

↑ Vegetarian food served at Koya-san monastery. The bowl in the center of the foreground contains simmered Koya-Tofu. (Both photos courtesy of Wakayama Tourism Federation) On the other hand, "Shimi-Tofu"(Shimi also means frozen in Japanese) is said to have been first produced around the Momoyama period (1573-1603) in frigid regions where the temperature drops below zero in winter. The tofu is made by repeatedly freezing and drying in sunlight by weaving slices of firm tofu with straw and hanging them outside in the winter. In Nagano Prefecture, surrounded by the Japanese Alps and other mountains, Shimi-Tofu became popular as a winter side job for farmers and became a production area. Today, Nagano Prefecture is a significant producer of Kori-Tofu, accounting for 98% of the total production in Japan. However, because mass production is now possible using the "artificial freezing" method, which is not affected by weather conditions, only a few people produce frozen tofu traditionally.

↑Shimi-Tofu is made by slicing hard, firm tofu.

↑ They hang the tofu under the eaves during the cold season when the temperature drops below zero to freeze and dry repeatedly.

↑ The traditional method is to weave sliced tofu with straws and hang them up.

2. The nutrients in Kori-Tofu

Kori-Tofu is made from "soybeans," also known as the "meat of the field," and is concentrated with the nutrients of soybeans. Of the approximately one piece, about 20 grams (103 kilocalories) of Kori-Tofu commonly available on the market contains 9.6 grams or almost half of vegetable protein. It is the equivalent of 240 ml of milk. Since an adult male's average daily protein requirement is 50 grams, you can calculate that eating just 5 sheets of Kori-Tofu is enough to meet the daily requirement. The key is that it contains plenty of "vegetable" protein, which is harder to obtain than animal protein from meat, fish, and dairy products. A 20 gram serving of Kori-Tofu contains 130 mg of calcium, almost the same as a 300 gram serving of silken tofu. One piece of Kori-Tofu provides about 20% of the average daily calcium requirement of 650mg for adult males. Of the 33.2% of fat in Kori-Tofu, about 80% is unsaturated fatty acids that reduce neutral fat and bad cholesterol, maintain healthy blood vessels, and prevent high blood pressure. Compared to meat and dairy products, this is an attractive way to consume healthy fats. Since it is also rich in iron, it is recommended for preventing anemia. Like tofu and other soybean products, it is also rich in soy isoflavone, which has a function similar to that of the female hormone estrogen, soy saponin, which promotes fat metabolism, lecithin, which stimulates brain activity, vitamin E, which prevents aging, magnesium, and dietary fiber, which is especially good for women. Compared to grains and potatoes, the amount of carbohydrates in Kori-Tofu is very little, so it is gaining attention as an ingredient for low carbohydrate diets. In particular, you can use the powdered "powdered tofu" (photo above, center) to make gluten-free snacks and sweets instead of flour. Not only for its nutritional value but also because it is plant-based, Kori-Tofu is attracting attention as an ingredient that can add satisfaction to vegetarian and vegan dishes. (Source: Japanese Food Standard Tables of Food Composition, Fifth Revised and Expanded: Ministry of Education, Culture, Sports, Science, and Technology)

3. Recipes using store-bought Kori-Tofu

If you have access to Kori-Tofu in your country, try making the traditional Japanese dish, "Fukumeni." We will also provide you with instructions on making it fluffy and soft. We will also show you how to make a pasta sauce to please vegetarians and a nutritious French toast. <The basic method for rehydrating store-bought Kori-Tofu> 1. Prepare a bowl of hot water (about 50°C) and place the Kori-Tofu in it so that it floats. 2. Soak in the water for about 10 minutes until the water soaks into the center, then gently squeeze out the water between the palms of your hands. 3. Cut into pieces of the desired size. You can also buy Kori-Tofu that does not need to be soaked in water or use water rehydrate. <A quick method for rehydrating frozen tofu in the microwave> 1. Prepare a bowl with plenty of water and soak the Kori-Tofu for 3 minutes to moisten. 2. Place the tofu on a heatproof plate, cover with plastic wrap, and microwave for 2 minutes at 500W. 3. Carefully remove from the microwave and cut into desired size pieces. *Drain and store in a zipper bag for up to 3 days (refrigerated) or up to 1 month (frozen). <Fukumeni(Simmered tofu and vegetables in Dashi broth)> This is a recipe for the most basic stew using Kori-Tofu. Ingredients (for 2 persons) Kori-Tofu: 2 slices (rehydrated and cut into bite-sized pieces) Carrots: 4 slices (about 2 mm thick) Shiitake mushroom: 2 pieces Green beans: 2 Dashi broth: 400cc (if you are a vegetarian, use kombu dashi; otherwise, use bonito dashi)  2 teaspoons light soy sauce Sugar: 2 1/2 tbsp Sake and Mirin: 1 tbsp each A pinch of salt Directions 1. Cut off the stems from the shiitake mushrooms. Remove strands from green beans, blanch, and cut them in half. 2. Pour the Dashi broth and seasonings into a pot, add the carrots and shiitake mushrooms, bring to a boil, remove the scum, and add the rehydrated frozen tofu. Cover and simmer for 8 to 10 minutes. 3. When the broth has reduced, turn off the heat and leave to cool down for a while to allow the flavors to soak in. 4. Arrange in a colorful dish and garnish with green beans. Below are two simple Western-style recipes to get you started.

<Tomato Sauce with Kori-Tofu> Ingredients (for 2 persons) 3 pieces of rehydrated Kori-Tofu 1 tablespoon olive oil 1/2 onion (finely chopped) 1 can whole tomatoes Salt and pepper: as needed 1. Finely chop the frozen tofu or use a food processor to make it into minced pieces. 2. Sauté the onion in a pan with olive oil, and add 1. 3. Add a can of whole tomatoes and simmer over low heat for 10 minutes, season with salt and pepper. Add red wine and spices to taste. Serve as a sauce for lasagna, pasta, etc.

<French Toast with Kori-Tofu> A fantastic dish that uses frozen tofu instead of bread! Ingredients (for one person) 1 piece of rehydrated Kori-Tofu 1 cup milk 1 teaspoon sugar 1 egg Butter: 20 grams Fruit and syrup to taste 1. Put the milk and sugar in a saucepan, add a piece of rehydrated Kori-Tofu, and simmer over low heat for 5 minutes, turning it with a spoon so that it soaks up the milk well. Be careful not to let it burn. 2. Crack an egg into a bowl, add the halved 1. and let it marinate for 10 minutes. 3. Melt 20g of butter in a frying pan over medium heat and grill the tofu on both sides over low heat until golden brown. 4. Serve with maple syrup, chocolate syrup, fruit toppings, etc., as desired!

4. Recipes using homemade Kori-Tofu

If you can't find Kori-Tofu on the market, don't be discouraged! Here is a simple way to make frozen tofu at home. Try it out! <How to Make Homemade Frozen Tofu> As the name suggests, frozen tofu is made by freezing tofu. As per the Kori-Tofu, they usually dried the tofu thoroughly. However, we will show you how to make frozen tofu without drying. Enjoy the sponge-like appearance and unique texture(Photo above). The texture will change depending on the freezing temperature and time. 1. Remove hard tofu from the container, drain, and wrap tightly with two or three layers of kitchen paper. 2. Place the tofu wrapped in kitchen paper on a bat or plate and leave it in the refrigerator overnight to drain further. 3. Cut the drained tofu into 6 to 8 pieces, wrap each piece in plastic wrap, place in a zipped bag, remove all air, and put in the freezer overnight. 4. When cooking, defrost the tofu in the plastic wrap by placing it in boiling water. Remove the plastic wrap and squeeze gently to drain the water, then cut the tofu into the desired size for cooking. *Homemade frozen tofu should be stored in the freezer and consumed within a month. Thawed tofu will not keep as long, so cook immediately after thawing.

<Deep-fried Frozen Tofu> 1. Squeeze out the water and cut the frozen tofu into bite-sized pieces. Squeeze out all the water. 2. Season lightly with your favorite seasonings and spices, then dust with flour or cornstarch and deep-fry in oil. *Enjoy the different textures from commercial soy meat. Of course, you can also shred it in a food processor and use it instead of ground meat, add it to soups, use it as tempura, or sauté it in olive oil.

5. Summary

We introduced you to the traditional Japanese preserved food, frozen tofu. I hope you now understand that it is a unique foodstuff born in Japan in terms of nutrition and its history, production method, and unique texture.

Actually, Kori-Tofu has been eaten in space!  

In July 1994, Chiaki Mukai, the first Japanese female astronaut, ventured into the space aboard the Space Shuttle Columbia. The space food she brought with her was stewed Kori-Tofu in the shape of a pocket, stuffed with minced meat and chopped vegetables(photo above, behind the stewed Kabocha). The fact that the freeze-drying process required for processing space food is the same as the traditional freeze-drying process for Kori-Tofu, was a major advantage in keeping the texture the same when eaten in space.

In Japan, "soy meat" is becoming increasingly popular as a meat substitute, and is increasingly seen on the menus of hamburger chains and cafes. Soybean meat is a food that meets the new health-conscious needs of the Japanese people, but Kori-Tofu, a traditional preserved food, is also a health functional food derived from soybeans that was created in the Japanese climate.

Japan has a lot more unique ingredients that you may not know about! Vegetarian, vegan, gluten-free, allergy-friendly, low-sugar, etc., the food world is now required to meet a variety of diverse dietary needs.

Let JCI's experienced instructors help you navigate this new world of Washoku.

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