Kansui is the alkaline ingredient that gives ramen noodles their characteristic springy texture and yellowish color.
Kansui is traditionally an alkaline mineral water containing compounds such as potassium carbonate and sodium bicarbonate. When added to wheat dough, it raises the dough’s pH and changes the behavior of its proteins. The result is a firmer, more elastic noodle with a distinctive bite and color.
Some modern manufacturers use a powdered substitute or baking-soda-based mixture instead of naturally sourced kansui. This ingredient is why ramen noodles differ from ordinary wheat noodles even when both contain flour and water. Miso is a fermented soybean seasoning, dashi is a Japanese stock, and mirin is a sweet rice wine; none of these creates ramen’s characteristic noodle texture.