Science Behind the Noodle

Kansui is a mixture of sodium carbonate and potassium carbonate which form an alkaline solution (pH ~9) when mixed with water. Wheat flour contains a number of compounds called flavones and trans-ferulic acid which are bound to starch and therefore colorless or white. The addition of an alkaline solution to wheat flour changes the pH of the mixture which in turn detaches these flavones (specifically apigenin glycosides) and trans-ferulic acid from starch and allows their natural yellow color to manifest.

Another reason for the addition of kansui is to toughen the protein in wheat flour so that the resulting noodles are firmer, more elastic and springy texture and less sticky when cooked. The addition of Kansui allows the use of lower protein (and therefore less expensive) wheat flour to make noodles with the quality one would expect of noodles made with superior quality flour with higher protein levels.