Japan — tofu production from soybean technology imported from China during Tang dynasty period (7th-8th century); refined through Kyoto's monastic vegetarian cuisine; distinct Japanese regional styles developed from Heian period onwards
Tofu production is a craft of precise physical chemistry: soaking dried soybeans, grinding them with water into a slurry (go), heating the slurry, separating the soy milk (tonyu) from the okara (pulp), then coagulating the soy milk into a gel with a coagulant (nigari or calcium sulfate) at precise temperatures. The coagulant type determines the texture of the resulting tofu: nigari (苦汁, natural mineral salts extracted from seawater, primarily magnesium chloride) produces tofu with a more complex, slightly bitter, mineral-forward flavour and a tender, irregular texture that artisan producers prefer; calcium sulfate (sumashi-ko) produces a more uniform, blander, firmer tofu preferred for industrial production where consistency matters more than flavour. Understanding the distinction is critical to tofu selection: premium artisan tofuya use nigari from specific sea areas; industrial producers use calcium sulfate at scale. The pressing stage determines the final texture: unpressed (silken/kinugoshi) = soft, custard-like; lightly pressed (semi-firm) = medium; heavily pressed (momen) = firm. Regional tofu traditions reflect local water quality: Kyoto's soft water produces exceptionally smooth, delicate tofu (Kyoto-dōfu) that is among the world's finest; harder water areas produce denser tofu. Okinawa's shima-dofu (島豆腐) is extremely firm, made without pressing by using more coagulant — it can be cut into cubes and fried without falling apart, reflecting the island's stir-fry tradition (chanpuru).
Nigari tofu: slight mineral bitterness, sweet soybean base, complex flavour; calcium sulfate tofu: blander, neutral; silken texture: custardy, rich mouthfeel; firm texture: dense, slightly chewy; Okinawan shima-dofu: resilient, absorbs surrounding flavours completely during cooking
{"Nigari coagulation: magnesium chloride from seawater creates more complex, mineral flavour than calcium sulfate","Temperature at coagulation: 70-75°C optimal; too hot creates grainy texture; too cold = incomplete setting","Pressing determines texture: from silken (no press) to firm (heavy press); pressed water = whey equivalent","Water quality impact: soft water = smooth, delicate tofu; hard water = denser, firmer result","Shima-dofu (Okinawa): exceptionally firm, made for stir-fry applications; different ratio of coagulant creates different protein network","Fresh consumption: artisan tofu consumed within 24 hours has noticeably superior flavour to stored commercial tofu"}
{"Fresh artisan tofu test: a fresh tofu block has a sweet soy milk smell; stale tofu smells flat or slightly sour","Agedashi dōfu: firm/momen tofu only; silken tofu is too delicate for deep-frying without special handling","Tofu in miso soup: add silken tofu in the last 30 seconds before serving — gentle heat only","Okara (tofu pulp): a valuable by-product; used in unohana (okara simmered with vegetables and seasoning)","Frozen tofu transformation: freezing creates a honeycombed sponge structure that absorbs braising liquids dramatically"}
{"Using tofu directly from refrigerator without temperature adjusting — cold centre creates uneven cooking","Pressing kinugoshi (silken) tofu the same way as momen — silken is not designed for pressing; crumbles","Draining silken tofu with paper towels instead of light patting — surface-dry only; excessive moisture removal changes texture","Cooking in water above 100°C — boiling creates unpleasant pocks in silken tofu surface (as in chawanmushi discussion)","Ignoring the difference between nigari and calcium sulfate brands when cooking — flavour and texture differ measurably"}
Tsuji Culinary Institute — Tofu Craft and Japanese Soybean Preparations