Hydration, Kansui, and Flour: the 3 things that decide a Chinese noodle

Noodle-supplier catalogs are full of terms like “medium-thick straight,” “high-hydration,” and “made with semi-strong flour.” You’ve picked noodles more or less by feel and used them, but somehow they never quite match your soup. And when it’s time to choose the next noodle, you have no idea what to compare them by.

The texture, color, and aroma of Chinese noodles are decided almost entirely by three things: hydration, kansui, and flour. Taisei Kikai Kogyo, a noodle-machine manufacturer, explains what each of these three does to the noodle at a mechanical level, and how to combine them to design a noodle that matches your soup. It is foundational knowledge you can use both when choosing supplier noodles and when considering making your own.

1. What does hydration decide about a noodle’s texture?

Hydration is the ratio of the weight of the mixing water (water with kansui and salt dissolved in it) to the weight of the flour. For example, adding 350 g of mixing water to 1 kg of flour gives a hydration of 35%.

In a low-hydration dough with little mixing water, the protein in the flour cannot absorb all the water, producing a hard, tightly bound dough. As a result, the noodle has a crisp bite and absorbs soup readily after boiling. Conversely, in a high-hydration dough with plenty of mixing water, the protein absorbs enough water and stretches well, producing a chewy, elastic noodle that absorbs soup less readily and holds up longer.

*The hydration brackets are a guide based on this site’s “Cutting-blade number and hydration design data” and “How to choose a ramen noodle machine.” The standard for what each is called differs by shop and noodle maker.
*If the table is cut off, scroll sideways to view it.

Hydration also affects how easy the noodle is to make. A low-hydration dough is hard, so it puts a heavy load on the machine’s rollers and gears as the dough is rolled out, while a high-hydration dough tends to stick to the rollers. That is why the power and the ease of cleaning demanded of a noodle machine change depending on the noodle you want to make.

Being able to choose for yourself which hydration suits your shop’s soup is a strength of in-house noodle making that supplier noodles cannot offer. When you make the noodle yourself, you can shift the bite and elasticity little by little and keep refining it toward the one bowl that best matches your soup.

2. What does kansui do to a Chinese noodle?

Kansui is an alkaline food additive used in Chinese noodles. Under Japan’s national standard, it is made from potassium carbonate (anhydrous), sodium bicarbonate, sodium carbonate, and the potassium or sodium salts of phosphoric acids — one of these, or a blend of two or more, either as is, dissolved in water, or diluted with flour. Not used in udon or somen, kansui is what makes a Chinese noodle a Chinese noodle.

Kansui causes three changes in the noodle.

• Color: a pigment in flour called flavonoid has almost no color on its own, but when placed in an alkaline environment its molecular structure changes and it turns yellow. That is why Chinese noodles are yellow.
• Koshi (firmness): the mesh structure (gluten) formed by the flour’s protein tightens and grows denser in an alkaline environment, producing a noodle harder and more elastic than udon.
• Aroma: boiling an alkaline dough changes components of the flour, producing the aroma distinctive to Chinese noodles, sometimes called the kansui smell.

The composition of the kansui also changes the result. In general, kansui high in potassium carbonate tightens the noodle firmly, while kansui high in sodium carbonate tends to leave a supple elasticity. Too little kansui and the noodle does not taste like a Chinese noodle; too much and bitterness and harshness come out easily, so kansui is added in smaller amounts than the other ingredients and adjusted carefully.

Source: Ministry of Health, Labour and Welfare, “Standards for Foods, Additives, etc.,” manufacturing standards for additives (kansui) (confirmed October 26, 2026)

3. How does your choice of flour change the noodle’s foundation?

Flour makes up most of a Chinese noodle’s ingredients and sets the foundation of the noodle’s firmness and flavor. The clue when choosing flour is the strength of the gluten formed by the flour’s protein.

The protein in flour forms gluten — a sticky, elastic structure — when water is added and it is kneaded, and this becomes the source of the noodle’s koshi. The amount and quality of gluten differ by the wheat and the type of flour, and the stronger the gluten, the firmer the noodle.

Japan has no official definition or standard for flour, but flour millers manufacture and sell flour in roughly four groups according to the strength of the gluten.

• Strong flour: the strongest gluten. Used for bread and gyoza wrappers.
• Semi-strong flour: the next strongest after strong flour. Used for Chinese noodles.
• Medium flour: medium gluten. Used for udon and other Japanese noodles.
• Weak (cake) flour: little gluten and soft in quality. Used for confectionery and for thickening dishes.

Source: Flour Milling Industry Association, “Processing of Flour and Its Products” (confirmed October 26, 2026)

Beyond gluten strength, flour also differs in aroma and color by the origin and brand of the wheat. Some shops blend two or more flours of different character, rather than a single flour, to achieve both texture and flavor.

4. How should you combine the three elements?

Hydration, kansui, and flour are not decided separately. For example, even at the same hydration, a protein-rich flour absorbs more water, so the firmness of the dough changes. Adding more kansui strengthens koshi, but if the hydration stays low, the noodle can become too hard.

When thinking about the combination, start from the soup.

1. Check the richness of the soup (rich or light).
2. Decide whether the noodle should absorb the soup or cling to it without absorbing, and set the direction of the hydration.
3. From the koshi you want, decide the type of flour and the amount of kansui.
4. Decide the thickness of the noodle by how it clings to the soup.

The thickness of a noodle is decided by the number of the blade (cutting blade) that cuts the noodle on the machine. Combinations of blade and hydration by soup richness are covered in detail in Cutting-blade number and hydration design data. The meanings of ingredient and process terms can be looked up in the ramen glossary.

5. How do in-house noodle shops use the three elements?

The use of the three elements shows clearly in the noodles of shops that have installed the Taisei noodle machine.

Source: Taisei Kikai Kogyo, “Introducing shops that use Taisei” (confirmed October 26, 2026)

Both shops decide the flavor of the soup first, then choose the flour and hydration to match that flavor. When you make noodles at your own shop, you can combine these three elements by your own judgment and decide them while confirming through trial batches.

6. How to test your noodle design (with the Taisei noodle machine)

The Taisei noodle machine is a commercial noodle machine with over 30 years of history: Taisei Kikai Kogyo handles design and manufacturing, and the sole distributor Kitchen Techno handles sales and post-installation training. There are ways to actually make and check noodles with varied hydration and blends.

• Free ramen school: a one-day hands-on demonstration that Kitchen Techno holds once a month each in Tokyo and Osaka, and irregularly in Sapporo. On real equipment, you learn how to use the machine and how to choose hydration, blends, and cutting blades, and you make and taste trial noodles and soup.
  Tokyo venue: Tenpos Tokyo Ramen Senmonkan (2-1-14 Higashi-Ayase, Adachi-ku, Tokyo)
  Osaka venue: Tenpos Osaka Ramen Senmonkan (2-1-8 Kitajima, Suminoe-ku, Osaka)
• Rental: from 62,000 yen a month, you place it in your own kitchen and make trial noodles that suit your own soup. You can also discuss switching to a purchase once you are satisfied.
• Early delivery: the standard No.2 keeps stock for early delivery and, when in stock, can be delivered within 1–2 weeks domestically. A reconditioned used machine, when in stock, can be delivered in as little as one week.

There are three models: the No.1, for small shops and small trial batches; the standard No.2, chosen by the most shops; and the No.3, for large-volume preparation. Every model comes standard with a mixer and supports swapping cutting blades #14–#28, so one machine can make noodles differing in thickness and hydration. Body prices are 1,688,000 yen for the No.1, 1,875,000 yen for the No.2, and 2,475,000 yen for the No.3 (all excluding tax, as of October 2026); a Stainless Version, resistant to rust and free of paint peeling, has also begun build-to-order across all models (price on inquiry).

On the cost side, the difference between supplier noodles and house-made noodles is about 24 yen per ball, which comes to about 720,000 yen a year for a shop serving 100 bowls a day, 25 days a month (as of October 2026, our research). The detailed way of thinking about costs is explained in Making your own noodles: is it better to “buy” or “rent”?

7. Frequently asked questions

Once you understand the three — hydration, kansui, and flour — you can choose noodles by their match with your soup rather than “by feel.” Next time you choose a noodle, consider whether what your current soup lacks is bite, koshi, or cling.