# 台灣豆乾完全圖鑑: A Physical Field Guide to Taiwanese Dougan

A deep guide to the varieties of 豆乾 (dougan / dried pressed tofu) sold in Taiwan, organized strictly by their **physical properties**: how each is produced, how it feels in the mouth, how it tastes, and where its color comes from. Cultural history, regional folklore, and brand stories are left out on purpose. Where sources disagree or a "fact" is actually marketing or legend, that is flagged.

The core insight behind this guide is the one you noticed growing up: **"豆乾" is an umbrella term, not a single food.** Products sold under it span at least six different production routes. Some are pressed bean curd, some are rolled bean-curd skin, some are deep-fried, some are fermented, and one of the most common (百頁豆腐) is not really tofu at all. Texture differences you taste are not random. They track three physical variables:

1. **Water content** set by pressing (less water = firmer, chewier, more protein-dense).
2. **The coloring and braising step** (caramel 糖烏 vs. soy braise vs. food dye vs. smoking), which changes surface color, saltiness, and how much the piece shrinks.
3. **The base material itself** (pressed curd vs. skimmed skin/yuba vs. reconstituted soy-protein slurry vs. fried or fermented derivatives).

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## 1. How the family is built: from soybean to dougan

Every product in this guide branches off a shared early pipeline, then diverges.

**The shared base chain:** soybeans (黃豆) are soaked, ground, boiled, and filtered into soy milk (豆漿). A coagulant is stirred in (點滷), which sets the milk into soft curds (豆花). The curds are ladled into a cloth-lined mold and pressed to expel water and lock the shape, giving tofu (豆腐). To make dougan, blocks of tofu are pressed **a second time** under more weight for longer, driving out still more water, and then optionally boiled, braised, baked, smoked, or fried.

So the single most important physical fact is this: **dougan is just tofu that has been pressed harder and dried further.** Everything firmer than soft tofu sits on a water-content ladder, and pressing is what moves a piece down it.

**The coagulant matters for texture.** Three are common in Taiwan:

* **石膏 (gypsum, calcium sulfate):** cheap, adds a lot of calcium, gives a fine, dense, smooth (綿密) curd. Most board tofu and much dougan uses it. This is also why dougan is so calcium-rich: most of the calcium comes from the gypsum, not the bean.
* **鹽滷 (nigari, mostly magnesium chloride):** more expensive, gives a coarser (較粗) texture, and takes more skill to set well.
* **GDL (葡萄糖酸內酯):** low mineral content, used for very soft tofu and 豆花, and in many industrial boxed-tofu and processed lines. Adds no calcium.

**The firmness ladder**, softest and wettest at the top:

| Stage | Coagulant route | Approx. water | Feel |
|---|---|---|---|
| 豆漿 soy milk | none yet | ~93% | liquid |
| 豆花 / 嫩豆腐 soft tofu | GDL | ~90% | silky, fragile, breaks easily |
| 板豆腐 firm tofu | gypsum or nigari | high but pressed | solid, springy (紮實綿密) |
| 白豆乾 white dougan | pressed twice | lower than tofu | firm, still moist, perishable |
| 五香 / 滷 dougan | pressed + braised | lower still | medium-firm, chewy |
| 黑豆乾 / 茶乾 | pressed + long braise/dry | lowest of pressed types | dense, very chewy (Q彈) |
| 豆皮 / 腐竹 yuba | skimmed film, dried | under 60% | thin, dry, chewy |

A useful number to anchor the ladder: firm dougan runs about **200 kcal, 19 g protein, and 334 mg calcium per 100 g** (one widely-cited figure; a denser 小方豆乾 measures closer to 17 g protein and 685 mg calcium per 100 g). Compare board tofu at roughly **88 kcal, 8.5 g protein, 140 mg calcium**, and soft tofu with about half the protein of firm tofu. The jump in protein and calcium density is purely the result of removing water. No Taiwanese source gives a standardized moisture percentage for dougan itself; they only ever say "lower than tofu," so treat the exact figure as an open gap.

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## 2. Master comparison table

All varieties, side by side, by physical property. "Base material" tells you which production route the piece comes from, which is the real reason two things that look similar can feel totally different.

| Variety | Base material | Key production step | Texture / mouthfeel | Color | Taste |
|---|---|---|---|---|---|
| **白豆乾** White dougan | Pressed bean curd | Tofu pressed a second time, no coloring | Firm, solid, still moist; perishable | Dull off-white (暗白色) | Pure soybean, unseasoned |
| **黑豆乾** Black dougan | Pressed bean curd | Braised in 糖烏 caramel ~15 min | Dense, chewy, springy (Q彈), tough skin | Deep coffee to near-black surface, white interior | Faintly sweet caramel, savory if five-spiced |
| **五香豆乾** Five-spice | Pressed bean curd | Braised in soy + five-spice + caramel | Medium-firm, "軟硬適中" | Light coffee-brown | Mild herbal-savory (star anise, licorice, cassia) |
| **滷豆乾 / 大溪豆乾** Braised / Daxi | Pressed bean curd | Repeated braise cycles or long wok-braise then dried | Springy and firm (彈牙紮實), small interior air-holes | Soy-brown skin, cream (米黃) interior | Savory, mellow, often lightly smoky |
| **茶乾 / 黃金豆乾** Snack / golden | Pressed bean curd, heavily pressed | Hard pressing, then braise or dye | Very firm, dense, sliceable, snappy | Golden-yellow to brown | Concentrated savory; eaten as a tea snack |
| **煙燻豆乾** Smoked | Pressed bean curd | Steam-set then smoked over wood or sugar | Firm, dense, defined bite | Mahogany / brown, glossy skin | Smoky, faintly sweet, mild salt |
| **豆乾絲 / 干絲** Shredded | Pressed bean curd, sliced and cut | Block sliced to sheets, cut to strands | Firm chewy strands; mushy if over-blanched | White to pale yellow, or braised brown | Mild soy; carries dressings |
| **百頁豆腐** Baiye tofu | **Reconstituted soy protein** | Soy-protein + starch + oil emulsified, cast, steamed | Smooth, bouncy, springy like fish cake; very uniform | White, square | Bland alone; a sponge for sauce; high fat |
| **千張 / 百頁** Sheet | Pressed/stacked curd sheet | Curd pressed thin in many cloth layers, or stacked films | Thin, pliable, little chew; soaks up soup | Pale yellow / cream | Nearly flavorless on its own |
| **油豆腐** Fried tofu | Fried bean curd | Firm tofu deep-fried, low-temp puff then high-temp set | Crisp golden skin, spongy or hollow airy interior | Golden / amber outside, pale inside | Rich, fried aroma, slightly oily |
| **豆包 / 豆皮** Yuba | Skimmed soy-milk skin | Film lifted off simmering soy milk, folded; fresh or fried | Fresh: soft, melt-in-mouth. Fried: crisp, porous | Pale yellow fresh; golden-brown fried | Strong clean soybean aroma |
| **素雞** Vegetarian "chicken" | Rolled bean-curd skin | Skin/sheets rolled tight, bound in cloth, steamed to set | Chewy, firm, springy; **layered cross-section** | Browned braised surface, pale layered interior | Savory braised (soy, five-spice) |
| **臭豆乾 / 臭豆腐** Stinky | Fermented pressed curd | Pressed tofu soaked in 臭滷水 brine, then fried, braised, or boiled | Crisp shell, airy porous interior full of holes | Grey to ink-dark; yellow or black when fried | Pungent fermented aroma, savory |

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## 3. Deep profiles

### Group A: The pressed-curd core (the "true" dougan)

These all start from the same pressed bean curd. What separates them is almost entirely the **finishing step**: how long they braise, what colors them, and how much they dry afterward.

#### 白豆乾 (Plain white dougan)

**Production.** Board tofu cut into blocks and pressed a second time to expel water. Nothing is added: no braise, no color, no smoke. This is the raw, unfinished form of every other pressed-curd type below.

**Texture.** Firm and solid (質地偏硬且紮實), harder than board tofu but still holding noticeable internal moisture. Because it is rich in both protein and water, it spoils fast. Left at room temperature for a few hours it weeps water and turns wet-sticky to the touch. This perishability is the original reason the braising and coloring steps were invented: they drive off surface water and extend shelf life.

**Taste.** Its whole selling point is the clean, undiluted soybean aroma (純粹的黃豆香), with no seasoning to mask it.

**Color.** Dull, dingy off-white (暗白色). This is the genuine, natural color of all dougan before anything is done to it. Because plain white dougan looks less appetizing and keeps poorly, it is relatively uncommon on shelves.

#### 黑豆乾 (Caramel-braised black dougan)

**A myth to kill first:** everyday black dougan is **not** made from black soybeans. Its color comes from caramel. The base is ordinary white dougan (yellow soybean) dyed dark by braising.

**Production.** Finished white dougan is simmered in **糖烏**, literally "black sugar." 糖烏 is cane sugar (蔗糖 or 紅糖) slow-cooked over low heat until it carbonizes into a thick, slightly bitter caramel, the same family as 醬色 (caramel coloring). It is a deep coffee-brown liquid, diluted with water before use. Color depth is controlled by **time in the pot**: lighter pieces braise about 5 minutes, full black dougan about 15 minutes. Over-braising makes the piece bitter, so judging concentration and timing is the maker's main skill.

**Texture.** Longer braising means more shrinkage and water loss, so black dougan ends up **denser and chewier (較Q彈)** than the lighter or white versions, with a noticeably tougher outer skin, and it keeps longer. The dark, dense, chewy bite and the long braise are the same fact described two ways.

**Taste.** A faint clean sweetness from the caramel, plus whatever spice (usually five-spice) went into the braise. Eaten as-is as a snack, no cooking needed.

**Color.** Yellow-brown to coffee-brown to near-black on the surface depending on braise time. Crucial detail for spotting real caramel coloring: with natural 糖烏 the color sits on the **surface only**, so a cut cross-section is still the original white. The piece also bleeds slightly when wet-rubbed, and tints standing liquid a faint coffee color. (More on reading color in Section 4.)

#### 五香豆乾 (Five-spice dougan)

**Production.** White dougan braised in a seasoned liquid built from soy sauce, sugar (often rock sugar 冰糖, which both rounds the salt and glosses the surface), and a five-spice set: star anise (八角), licorice (甘草), cassia bark (桂皮), five-spice powder (五香粉), sometimes pepper and chili to cut the raw-bean note. A common technique is to caramelize the sugar first (the 糖烏 step) and add the spices to that, so coloring and flavoring happen together.

**Texture.** Medium, neither hard nor soft (軟硬適中), which is why it is the most broadly popular eating texture. A craft detail: braising with **no standing water** in the pan keeps internal air-holes from forming, giving a denser "軟Q" body; braising with water opens up holes.

**Taste.** Mild and savory with a faint Chinese-medicine herbal note from the spices. The mainstream flavor of the category.

**Color.** Light coffee-brown (淺咖啡色).

#### 滷豆乾 / 大溪豆乾 (Braised dougan, Daxi style)

This is the dense, dark, snackable braised dougan most associated with Daxi (大溪). Treated here purely for what makes it physically distinct.

**Production (note: maker-dependent, there is no single recipe).** Two documented routes from named Daxi makers:

* One repeatedly braises the pressed white dougan **three times in salted black caramel, then three times in five-spice brine**, so both color and flavor saturate every layer.
* Another seasons the dougan and **stir-fries it in a roughly 100°C wok for about 80 minutes, then machine-dries it about 45 minutes**, then rests it in air conditioning to drip off oil.

Both produce a leisure-snack dougan; they are just different factory methods. Industrially the sequence is mold and press to set, demold and cut, surface-treat with alkali (上鹼) and air-dry, pass through a hot pan for 醬色 coloring, then cold-air dry around 12°C to pull off surface moisture before vacuum packing.

**Texture.** Springy yet firm and substantial (彈牙紮實), with a soy-color skin over a cream-colored (米黃) interior that carries small air-holes from braising. Firmer overall than white dougan, with a heavier flavor.

**Taste.** Savory and mellow with an inherent smoky note. Eaten straight as a snack; the red-brown stir-fry grade is the one cooked with celery or garlic chives.

**Color.** Soy-brown to dark skin from repeated braising, cream interior. (The lore that Daxi's local soft water makes the dougan better is repeated everywhere but the sources themselves frame it as legend (相傳) with no measured backing, so do not treat water hardness as a verified cause of texture.)

#### 茶乾 / 黃金豆乾 (Firm snack dougan / golden dougan)

**What "茶乾" actually means.** Despite the name, 茶乾 is generally **not tea-infused**. The term refers to small, very firm, dense pressed dougan eaten as a snack with tea. No authoritative Taiwanese source confirms tea or turmeric as an ingredient in the golden commercial product. The firmness comes from heavy pressing, and the golden-yellow color comes from caramel plus permitted yellow food dye, not from tea.

**Production.** Engineered mainly through **press strength**: the harder and longer the press, the flatter, drier, firmer, and more sliceable the result. Golden color is added with caramel (焦糖色素) plus food yellow No. 4 (Tartrazine) or No. 5 (Sunset Yellow). Natural yellow options exist (梔子/gardenia, 胡蘿蔔素/carotene, buckwheat, cacao) but are unstable and rarely used commercially.

**Texture.** The firmest, densest, most snappy of the pressed types. Dense enough to slice thin for stir-fries or to eat as a chewy snack.

**Taste.** Concentrated and savory; the uncolored, unseasoned firm grade has the purest, most concentrated soybean aroma of any dougan because nothing masks it.

**Color.** Golden-yellow if dyed, or natural brown if caramel-braised. A bright, vivid yellow specifically signals added dye rather than caramel (caramel can never produce a vivid yellow).

#### 煙燻豆乾 (Smoked dougan)

**Production.** Seasoned dougan is steam-set, then smoked over a smoking material (wood, or sugar in the 糖燻 method, where rock sugar 冰糖 contributes both browning and aroma). The surface keeps darkening after it leaves the smoker, so it is pulled before it looks fully done; over-smoking turns it burnt and bitter.

**Texture.** Firmer and more defined than fresh tofu because of the combined steaming and smoking; the smoked skin adds its own layer of chew.

**Taste.** Smoky, with enough salt and aroma in the skin that it needs little extra seasoning. The Daxi braised type already carries a smoky note some compare to smoked cheese.

**Color.** Brown to mahogany with a glossy sheen on the skin.

#### 豆乾絲 / 干絲 (Shredded dried tofu)

**Production.** Exactly the same material as block dougan, just cut into strands. A firm block of dried tofu (白干 / 大白豆干) is sliced horizontally into thin sheets, then cut into fine strands. So 干絲, 乾絲, 豆干絲, and 豆腐絲 are the same thing: shredded pressed tofu, a soy protein food, not a noodle despite the look. Commercial production often adds alkali (鹼) to improve texture, which leaves an alkaline taste that has to be removed at home by blanching or a baking-soda soak (去鹼).

**Texture.** Firm, springy strands when cooked right. Over-blanching makes them soft, mushy, and prone to breaking, which kills the texture. They are firm enough that people sometimes snip them shorter with scissors.

**Taste.** Mild and clean on its own, which is why it is almost always dressed (涼拌), braised, or stir-fried. White unbraised 干絲 has a fine texture and concentrated soy aroma.

**Color.** White to pale yellow plain; brown if braised in caramel brine.

**干絲 vs. 豆乾絲 nuance.** In everyday Taiwanese usage the names are interchangeable. The one real distinction is fineness: the Huaiyang 大煮干絲 tradition cuts extremely thin matchstick strands by knife (a single block split into many sheets), while the chunkier machine-cut strands sold for home stir-fries are coarser.

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### Group B: Skin and rolled forms (not pressed curd)

These come from **yuba**, the skin skimmed off heated soy milk, not from pressed curd. That is why their cross-section is layered rather than solid, and why they feel different even when braised the same way.

#### 豆包 / 豆皮 (Yuba bean-curd skin)

**Production.** When soy milk is held at a simmer, proteins at the surface denature, expose their water-repelling regions, and bond into a thin film (薄膜). That film is lifted off, and it is the yuba. Laid flat and folded layer over layer (like folding a quilt), wet film becomes fresh 生豆包. Fried at low temperature, it becomes crisp 炸豆包 / 油皮.

**Texture.** Fresh wet yuba is thin, soft, high in moisture, very delicate, almost melt-in-the-mouth. Fried yuba puffs, crisps, and turns porous, so it drinks up soup and sauce; it is also shelf-stable at room temperature.

**Taste.** A rich, clean, concentrated soybean aroma, stronger than most pressed dougan because so little is done to it.

**Color.** Pale yellow when fresh; golden to brown when fried.

**Related forms for contrast:** 腐竹 is the same film dried much longer and allowed to droop into rods, which makes it harder and more elastic. 千張 (next) is a stacked-sheet form.

#### 素雞 (Vegetarian "chicken")

**Production.** Sheets of yuba, 千張, 腐竹, or 豆包 are softened if dried, stacked, rolled tight into a cylinder, wrapped in cotton or burlap cloth, tied hard with string, and steamed to set. On cooling, heat expansion and contraction binds the layers into one cohesive body. Rolling as tight as possible is essential or the roll falls apart. A second industrial route presses and sets tofu by machine instead of hand-rolling.

**Texture.** Chewy, firm, and springy, with a **visibly layered cross-section** that is its defining structural signature, completely unlike the solid homogeneous body of block dougan. Commercial 素雞 is often alkali-treated, which makes it harder and better suited to long stewing.

**Taste.** Savory and braised: soy sauce, sugar, sesame oil, pepper-salt, five-spice. Often red-braised (紅燒) or pan-fried after steaming.

**Color.** Browned, braised exterior over a pale layered interior.

#### 千張 / 百頁 (Thin bean-curd sheet)

Important: this 百頁 is **not** 百頁豆腐 (Group D). They share a character but are entirely different foods.

**Production.** A thin, low-moisture sheet of bean curd. Sources give two mechanisms: one says the curd is wrapped in many cloth layers and pressed very firmly so it comes out as thin sheets; another (Cookpad) says thin layers of soy milk are heated into films in trays and stacked. Both yield a thin layered sheet; the method is a genuine point of disagreement.

**Texture.** Thin and pliable. One account calls it essentially chewless and flavorless, a vehicle that holds shape and soaks up soup; another calls it both springy and somewhat chewy. They agree it is thin and absorbent.

**Taste.** Nearly flavorless on its own.

**Color.** Pale yellow to cream.

**Use.** Cut into shreds, or into strips tied into knots (千張結), used as wrappers, or rolled up into 素雞 and vegetarian ham.

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### Group C: The processed imposter

#### 百頁豆腐 (Baiye tofu)

**The headline fact:** 百頁豆腐 is **not tofu**. It is a modern processed product, closer in principle to a fish cake (魚板) than to bean curd.

**Production / composition.** It is built from **soy protein (大豆分離蛋白 / 大豆蛋白, made by drying defatted soy milk), starch (澱粉 / modified starch), oil (大豆油 or other salad oil), water, and seasoning**, sometimes with egg white or a quality improver added for spring. These are uniformly emulsified into a slurry, poured into forming molds, and steamed, a process likened to baking a cake. Critically, it is made from "reconstituted soy milk" (還原豆漿 = soy protein plus water), not the raw soy milk (原生豆漿) that defines real tofu. Multiple independent authorities confirm this, including a National Taiwan University chemical-engineering analysis of the ingredient label and several registered dietitians. In mainland China the Taiwanese product was even renamed 千頁豆腐 (and variants) specifically to avoid clashing with the existing 百頁/千張 sheet, direct evidence of how routinely the two are confused.

**Texture.** Smooth, dense, uniform, and distinctly **bouncy and springy (Q彈)**, the closest thing in the tofu aisle to a fish cake or kamaboko. The steaming sets it firm enough to hold shape in stir-fries and hotpot, and its internal pores let it absorb large amounts of sauce.

**Taste.** Mild and bland alone. Its real function is as a sponge for high-salt, high-sodium braising liquid. It is calorie-dense and fatty for a soy product.

**Color.** White, square, tofu-like, which is exactly why the inventor called it "豆腐."

**The numbers (and a conflict to know):** Taiwan's Food Composition Database lists 100 g at about **196 kcal, 13.4 g protein, 13.1 g fat**, so fat roughly equals protein. Compare board tofu at 88 kcal and soft tofu at 53 kcal. Calcium is low (around 33 mg/100 g vs. 140 mg for board tofu) because it is not set with calcium sulfate. Popular media claim it is "70% oil," but the manufacturer rebuts this and puts fat at roughly **10 to 20% by weight**, comparable to Daxi dougan; the database figure (~13%) sits in that range, so "70% oil" is an exaggeration. The coagulant is also disputed: some food media say calcium sulfate, the maker says none (it sets on the soy protein's own gelling), and a food-science source lists only a "quality improver / thickener." What is consistent is the core recipe (soy protein, starch, oil, water, emulsified and steamed) and one unusual physical property: it **freezes and thaws with almost no texture change**, rare among soy products.

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### Group D: Fried and fermented derivatives

#### 油豆腐 (Fried tofu, 豆腐泡 / 三角油豆腐)

**Production.** Firm board tofu (老豆腐, lower water content puffs best) is deep-fried. Industrially this is two stages: a lower-temperature fry to puff and expand, then a high-temperature fry to set the shape and color. Traditional shops literally keep two oil vats for this.

**Texture.** A crisp golden skin over a soft interior, "更有層次" (more textural layers). As the internal water flashes to steam during frying, it pushes the block open into a sponge-like, honeycombed (蜂窩) interior full of air pockets, sometimes hollow. Small pieces (豆腐泡 / 豆腐果) tend to be hollow with a honeycomb interior; larger blocks (三角油豆腐, 厚揚げ style) stay denser inside, nearer to solid tofu. The interior is often described as soft and smooth like pudding, and the whole piece springs back when pressed.

**Taste.** Frying adds a rich aroma and an almost meat-like, fried-chicken quality. The skin carries a layer of oil that tastes greasy and blocks seasoning, so Taiwanese cooks blanch or rinse it (去油) before cooking, which also re-opens the pores for faster flavor uptake. Protein runs about 10% for solid fried blocks and up to ~18.6% for the puffed type.

**Color.** Golden to amber, smooth and glossy outside; pale inside.

#### 臭豆乾 / 臭豆腐 (Stinky tofu, firm and soft)

**Two distinct products.** 臭豆腐乾 is the firm, "dried" stinky type; 臭豆腐乳 is a fermented bean-curd "cheese" eaten as a condiment and never fried. This profile covers the firm and fried kinds, which overlap most with dougan because they start from **pressed firm tofu**.

**Production / fermentation.** Pressed white tofu blocks are soaked in a fermenting brine (臭滷水). The classic Taiwanese brine steeps the older parts of amaranth (莧菜) in rice-washing water at room temperature; other methods use inoculated microbial strains, or a long all-plant ferment (amaranth, bamboo shoot, mustard, etc. for eight months or more). Microbes in the brine break down the tofu's protein, loosening its structure (組織鬆弛) and creating the smell. A key modern caveat: Taiwan's mass-market fried stinky tofu is now mostly just **soaked 6 to 8 hours in a pre-made brine** and does not truly ferment, which is why some of it tastes like ordinary fried tofu.

**Texture.** The firm pressed type fries into a crisp shell over an airy interior riddled with holes (內含很多孔洞), "外脆裡鬆." Because it started as a pressed block, it needs longer frying to cook through and ends up chewier than the soft type. The firm form is also dropped un-fried into hotpot (臭臭鍋), or braised for 麻辣 and 清蒸 versions, where the porous body soaks up sauce and eats dense and creamy (綿密). Freezing first creates a honeycomb structure that boosts absorption, the same mechanism as 凍豆腐.

**Taste.** Pungent fermented aroma over a savory body; intensity tracks how truly it fermented.

**Color.** Varies widely by region and method: grey (灰) after brining, ink-dark (青墨色) all the way through in fully buried-fermented blocks, yellow-skinned (黃皮) or black-skinned (黑皮) once fried. Firm pressed stinky blocks tend toward tile-grey to grey-black with small surface bubbles when fried; softer stinky tofu stays grey-white before frying and only goes golden.

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## 4. The coloring science (cross-cutting)

Color in dougan is one of the most misread physical properties, so it is worth isolating. The natural color of all pressed bean curd is **dull off-white**. Every brown, black, or yellow piece got that way by one of these:

* **糖烏 / 醬色 (caramel from carbonized cane sugar):** the traditional Taiwanese colorant. Deep coffee-brown, water-soluble, and it can only ever produce brown tones, never a vivid yellow. Because it is water-soluble, it stays on the **surface**: a naturally caramel-colored piece has a white cross-section, bleeds a little when wet-rubbed, and tints standing liquid faint coffee.
* **醬油 (soy-sauce braise):** adds brown color plus salt and savor at the same time.
* **食用色素 4號 / 5號 (Tartrazine and Sunset Yellow, legal food dyes):** used for bright golden dougan. Unlike caramel, dye **penetrates** the cross-section, gives a vivid even yellow, and does not bleed into water. So a colored interior, or a bright vivid yellow, indicates dye.
* **焦糖色素 (manufactured caramel color):** comes in four classes; only Class I is truly "natural" caramel, and Class IV is the type once flagged for health concerns.
* **皂黃 / 二甲基黃 (industrial dyes):** illegal adulterants behind Taiwan's 2013 dougan dye scandal. Their whole point was to fake a bright cheap color faster, and they are why so much consumer coverage of dougan "color" is really about food safety.

**How to read a piece by eye:** brown surface plus white cross-section equals natural caramel; uniformly colored cross-section equals dye penetration; vivid bright yellow equals added dye; standing liquid turning coffee-colored equals caramel bleeding.

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## 5. The texture spectrum (cross-cutting)

Four physical processes move a soy product's texture, and most varieties are just combinations of them:

* **Pressing** removes water and tightens the protein network. More pressing equals firmer, drier, more sliceable, and more protein- and calcium-dense. This is the whole tofu-to-dougan move.
* **Braising and drying** shrink the piece through water loss and protein contraction. Longer cycles equal denser, chewier, darker, and longer-keeping. This is why black dougan is chewier than white, and the same principle (repeated braise plus wind-dry) is what makes iron eggs (鐵蛋) shrink small, dark, and rubbery.
* **Frying** flashes internal water to steam, puffing the piece into a spongy or hollow interior under a crisp skin. This makes 油豆腐 and fried stinky tofu.
* **Fermenting and freezing** loosen or restructure the protein into a porous, absorbent body (stinky tofu's holes; 凍豆腐's honeycomb).

Once you know which processes a piece has been through, its texture is predictable. A heavily pressed, long-braised, well-dried piece is dense and chewy by necessity. A fried piece is crisp-and-airy by necessity. A reconstituted-protein piece (百頁豆腐) is uniformly bouncy because it was an emulsion, not a curd, to begin with.

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## 6. Conflicts, naming traps, and gaps (honest notes)

* **百頁豆腐 ≠ 百頁 / 千張.** The first is the modern soy-protein-plus-starch-plus-oil processed block; the second is a thin plain bean-curd sheet. Same character, totally different foods. The China rename to 千頁豆腐 exists because of exactly this confusion.
* **干絲 vs. 豆乾絲** are interchangeable names in Taiwan; the only real difference is fineness (knife-cut Huaiyang 干絲 is matchstick-thin, machine 豆乾絲 is coarser).
* **茶乾** is a name for firm snack dougan eaten with tea, not a tea-flavored product. Tea or turmeric as ingredients in commercial golden dougan is unverified.
* **No standardized moisture percentage** exists in the sources for dougan; they only say "lower than tofu." Treat any exact figure with suspicion.
* **大甲, 關廟, 鹽水 dougan** did not turn up as verified physically-distinct types. Marketing copy describing 大甲豆乾 recycles the wording used for Daxi, and Guanmiao's documented specialties are noodles and pineapple, not a named dougan. Do not assume these are distinct varieties.
* **Daxi soft-water lore** (that local water makes the dougan better) is presented by the sources themselves as legend, not measured fact.
* **百頁豆腐 fat and coagulant** are disputed: fat is best stated as ~10 to 20% by weight (not "70% oil"), and the coagulant is variously reported as calcium sulfate, none, or an unnamed improver.
* **千張 production** has two competing descriptions (cloth-layer-pressed curd vs. stacked soy-milk films).
* **油豆腐 interior** ranges from hollow (small pieces) to spongy-but-nearly-solid (large blocks), depending on size and how firm the starting tofu was.

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## Sources

Production fundamentals, coagulants, nutrition density:
- 農業部 食農教育平臺, https://fae.moa.gov.tw/theme_data.php?theme=topics&sub_theme=material&id=1794
- 自由時報 食譜自由配 (tofu family / 油豆腐 / 百頁豆腐), https://food.ltn.com.tw/article/4663 ; https://food.ltn.com.tw/article/6922 ; https://food.ltn.com.tw/article/10977 ; https://food.ltn.com.tw/article/7284
- 好食課 learneating, https://views.learneating.com/food-tech/tofu-calories-calcium/ ; https://views.learneating.com/nutrition/soy-bean-product-processing-nutrients-for-dummies/
- 康健雜誌, https://www.commonhealth.com.tw/blog/4429
- 上下游 News&Market (coagulants), https://www.newsmarket.com.tw/blog/85991/

Coloring, 糖烏, and braised / Daxi dougan:
- 上下游 News&Market (糖烏 process, braise times, surface vs. cross-section), https://www.newsmarket.com.tw/blog/31443/
- PanSci 泛科學 (commissioned by 環境部), https://pansci.asia/archives/126916
- 環境部化學物質管理署, https://topic.moenv.gov.tw/chemiknowledgemap/cp-224-7744-ca998-5.html
- 玩咖 Playing / 自由時報 (Daxi 糖烏), https://playing.ltn.com.tw/article/8016/1 ; https://food.ltn.com.tw/article/7136
- 大溪豆干 維基百科, https://zh.wikipedia.org/zh-hant/%E5%A4%A7%E6%BA%AA%E8%B1%86%E5%B9%B2
- 台灣麒麟 (大房豆干 process), https://www.kirin.com.tw/blog/article/1617
- 徐仲 飲食文化 (natural pigments), https://hsuzong.wordpress.com/2015/01/14/染色的豆干/
- ETtoday / 食藥署, https://health.ettoday.net/news/2868547
- 得倫食品 (沙茶豆干 ingredient panel), https://www.dl-food.com/product/sandteadriedtofu/

Shredded, sheet, and 百頁豆腐:
- TechOrange / 謝玠揚 台大化工博士, https://buzzorange.com/techorange/2019/04/10/bean-curd-not-tofu/
- CitiOrange (maker side), https://buzzorange.com/citiorange/2020/07/20/hundred-layered-beancurd/
- 百頁豆腐 維基百科, https://zh.wikipedia.org/zh-tw/%E7%99%BE%E9%A0%81%E8%B1%86%E8%85%90
- 今周刊, https://www.businesstoday.com.tw/article/category/161153/post/201904080014/
- 呂孟凡營養師, https://www.dietitianbread.com/classic_topics/fun_facts/%E7%87%9F%E9%A4%8A%E5%86%B7%E7%9F%A5%E8%AD%9814/
- 千張 維基百科, https://zh.wikipedia.org/wiki/%E5%8D%83%E5%BC%B5
- 大煮干絲 維基百科, https://zh.wikipedia.org/wiki/%E5%A4%A7%E7%85%AE%E5%B9%B2%E4%B8%9D
- 自由時報 (干絲 去鹼/texture), https://food.ltn.com.tw/article/11934
- 小半天豆干味 (manufacturer flow), https://king-pin.ego.tw/multimedia1.html ; 春豐豆類食品, https://soypro.com.tw/生產流程/

Fried, yuba, rolled, fermented:
- 食力 foodNEXT (fried tofu mechanism), https://www.foodnext.net/life/culture/paper/6111026011
- 豆卜 維基百科, https://zh.wikipedia.org/wiki/%E8%B1%86%E5%8D%9C
- Cookpad Taiwan (豆皮 / 豆包 / 腐竹 / 千張), https://blog.cookpad.com/tw/tofu-skin/
- 夢幻廚房在我家 (素雞), https://dreamchefhome.com/%E7%B4%A0%E9%9B%9E/
- 臭豆腐 維基百科, https://zh.wikipedia.org/zh-tw/%E8%87%AD%E8%B1%86%E8%85%90
- 食力 foodNEXT (鐵蛋 mechanism), https://www.foodnext.net/issue/paper/4357939297 ; 今周刊 (鐵蛋 schedule), https://www.businesstoday.com.tw/article/category/183016/post/202207130042/

*Compiled June 2026. Physical-property focus; cultural and regional history deliberately excluded. Claims cross-checked across multiple Taiwanese sources where possible; remaining conflicts and gaps are flagged in Section 6.*