Soy milk, tofu and yuba: why the pot's shape matters
Soybeans become a drink, a set curd or a lifted skin depending on how the hot milk is held: still in a deep container, broken and pressed in a mould, or spread wide in a shallow pan.
Traditional method
Kōri-dōfu (frozen and dried tofu)
凍り豆腐 (kōri-dōfu) · kōya-dōfu · shimi-dōfu · kori-tofu · Iwadeyama kōri-dōfu
Japanese tofu frozen, aged below freezing, thawed and dried to a light sponge that is simmered in dashi; Iwadeyama makes it in winter air.
What kōri-dōfu is
Kōri-dōfu is tofu that has been frozen, aged below freezing, thawed and dried until it becomes a light, porous sponge. The name means frozen tofu. It is rehydrated before cooking and then simmered in dashi.
MAFF lists it among the processed bean products of Japan, beside koya-dōfu and shimi-dōfu, and describes it as a tofu made by drying. The Iwadeyama district of Miyagi is the best-known place where it is still made by the winter method.
Sources for this section
The Iwadeyama winter method
The documented Iwadeyama route runs from December to March. Tofu is made from Miyagi-grown soybeans and nigari, aged for about two weeks just below freezing, thawed, soaked to remove bitterness, tied with igusa rush, hung, frozen again and dried in the cold, dry winter air for about a week.
The freezing opens the curd into a sponge and the winter air dries it without heat. MAFF describes the method in these terms and gives no temperature for the ageing stage, so that figure is unknown here.
Sources for this section
Industrial production and modern studies
The FAO account of soybean protein products describes the industrial process, which differs from the Iwadeyama route. Tofu is set with calcium chloride, cut into tablets, frozen and held frozen for up to three weeks, thawed, pressed to remove much of its water, air-dried, cured with ammonia gas and packaged. Before use the blocks are rehydrated.
A 2022 trial of soy kōri-tofu used a product made with high-pressure pressing, freezing, ageing and drying to about 8 per cent moisture. A 2025 study compared frozen tofu aged at −3 °C with tofu aged at −21 °C; the warmer ageing hardened the tofu more. These studies describe production, not a home method.
Sources for this section
- Technology of production of edible flours and protein products from soybeans. Chapter 9. →
- Effect of 4-Week Consumption of Soy Kori-tofu on Cardiometabolic Health Markers: A Double-Blind Randomized Controlled Cross-Over Trial in Adults with Mildly Elevated Cholesterol Levels →
- Effects of ripening conditions on protein conformation and quality of frozen tofu prepared by different coagulants →
Making it at home
No home method for kōri-dōfu is documented in the work reviewed here. A home freezer can perform the freezing stage, but no source gives a drying endpoint, a moisture target or a safe way to dry frozen tofu at home. A frozen block that has not been dried is not yet kōri-dōfu.
Until a validated home route exists, the Iwadeyama method is the reference for the product and the industrial account is the reference for the process steps.
Sources for this section
History
MAFF documents the Iwadeyama tradition. It records the 1842 start as local tradition and the 1876 shipments from a district gazetteer. The regional name and the GI status are the best-attested facts about the product.
Ingredients
Scaling: source batch only
Quantity not given.
Nigari
Amount not stated
Iwadeyama coagulant; dose not given.Calcium chloride (optional)
Amount not stated
Coagulant in the FAO account of the industrial process, used instead of gypsum; dose not given.Method
Risks and precautions · Standard risk
Ammonia-gas curing is an industrial step in the FAO account and is not part of any home method.
A home-frozen block is not kōri-dōfu until it is dried; no home drying endpoint is documented.
- At Iwadeyama, production runs from December to March.
- Make tofu from Miyagi soybeans and nigari.
- Age the tofu for about two weeks at a temperature just below freezing (氷温; MAFF gives no figure).
- Thaw it, then soak it in water to remove bitterness.
- Tie the blocks with igusa rush and hang them.
- Freeze them again; MAFF presents this refreezing as particular to Iwadeyama.
- Dry them in the cold, dry winter air for about one week.
- Industrial route, kept separate (FAO): tofu set with calcium chloride is cut into square tablets, frozen and held frozen for up to three weeks, thawed, pressed to remove much of the water, air-dried, cured with ammonia gas and packaged.
- Before use, the dried blocks are rehydrated in water.
Places
Iwadeyama, Ōsaki, Miyagi
Traditional preparation · Locality evidenceThe GI-registered Iwadeyama kōri-dōfu.
Nara
Historical attestation · Locality evidenceLocal tradition says the forerunner method (hyō-dōfu) was learned here; no primary source dates it.
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Sources
Ministry of Agriculture, Forestry and Fisheries (MAFF), JapanMethod · History · Use
凍り豆腐（こおりどうふ）｜にっぽん伝統食図鑑：農林水産省December to March, Miyagi soybeans and nigari, two-week sub-zero ageing, thaw, soak, igusa, refreeze, one-week winter drying, 1842, 1876, GI 2018
Cited in: What kōri-dōfu is; The Iwadeyama winter method; Making it at home
FAO (Agricultural Services Bulletin No. 97, 1992)Method
Technology of production of edible flours and protein products from soybeans. Chapter 9.calcium chloride, up to 3 weeks frozen, press, air-dry, ammonia gas, rehydrate
Cited in: Industrial production and modern studies
Ministry of Agriculture, Forestry and Fisheries (MAFF), JapanDefinition
Processed bean products | Traditional Foods in Japan : MAFFkori-dofu made by drying; koyadofu, shimidofu
Cited in: What kōri-dōfu is
Nutrients 15(1):49 (MDPI), 2022Method
Effect of 4-Week Consumption of Soy Kori-tofu on Cardiometabolic Health Markers: A Double-Blind Randomized Controlled Cross-Over Trial in Adults with Mildly Elevated Cholesterol Levelshigh-pressure pressing, freezing, ageing, drying to 8% moisture
Cited in: Industrial production and modern studies
LWT – Food Science and Technology 238, 2025Science
Effects of ripening conditions on protein conformation and quality of frozen tofu prepared by different coagulants−3 °C vs −21 °C ageing
Cited in: Industrial production and modern studies