The Chinese-style alkaline noodles used in ramen are called chūkamen in Japanese.
Chūkamen are wheat-based noodles made with flour, water, salt, and kansui, an alkaline solution. Kansui changes the dough’s chemistry, producing ramen’s characteristic springy texture, pale yellow color, and firm bite. The noodles may be straight or wavy and can vary in thickness and length.
The term literally means “Chinese noodles,” reflecting ramen’s historical connection with Chinese-style noodle dishes. Ramen itself developed in Japan through Chinese culinary influence, but modern ramen has become a distinctly Japanese food with regional broths, toppings, and preparation methods.
Chūkamen are not the same as soba, udon, or sōmen. Soba is associated primarily with buckwheat, udon is thick and wheat-based without ramen’s characteristic alkaline treatment, and sōmen is very thin and often served chilled.
Kansui is also why ramen noodles behave differently from ordinary wheat noodles. The alkaline ingredient strengthens their texture and contributes to the flavor and color that diners associate with ramen.