1. What Does "Having Koshi" Mean for Udon Noodles?
Hearing "this noodle has koshi" might make you imagine a strand so hard you cannot cut it. However, one explanation states that koshi is not hardness itself.[1] The description of koshi is a state where the noodle feels smooth and pleasant in the mouth, but offers a satisfying resistance when chewed. There is no single strict definition for koshi, but this article focuses on the elasticity of the pushing-back force and the property of sticking together without breaking.
2. Gluten: The Rubbery Lump Left After Washing Flour
If you add water to flour, knead it well, soak it, and then wash it carefully, the starch and other components wash away, leaving a rubbery lump. Materials from a food manufacturing class at a high school in Kyoto Prefecture show how to extract this using both strong and weak flour.[3] This lump is gluten. It forms when two types of protein in flour, gliadin and glutenin, bind together when water is added and the mixture is kneaded. It is described as having properties that are sticky, stretchy, elastic, and resistant to breaking.[1] Furthermore, research reports from Kyoto University and others suggest that glutenin relates to elasticity, while gliadin relates to stickiness.[2] These are the two pillars of koshi.
3. How Salt Changes the Dough, Studied With X-rays
When making udon dough, salt is dissolved in the water mixed with the flour. It is explained that adding salt changes how the proteins interact, promoting the formation of gluten.[1] A study used X-ray scattering at the large synchrotron radiation facility SPring-8 to investigate this effect. When the concentration of salt water was changed, the way gliadin gathered changed significantly. On the other hand, no major differences were seen in glutenin, and it was reported that salt had a larger impact on gliadin.[2] However, this experiment examined glutenin and other components extracted with water. It was not the result of the udon dough itself. While people often say "salt tightens the mesh," the mechanism at the molecular level cannot be determined from this data alone.
4. Why Sanuki Udon Recipes Use More Salt in Summer and Less in Winter
Materials on how to make "Sanuki no Yume" udon in Kagawa Prefecture show the amount of salt used in the brine for each season. For 400 grams of flour, it is 23 grams in spring and autumn, 24 grams in summer, and 22 grams in winter.[4] The reasons are also listed. In summer, the dough becomes soft easily, so more salt is used and less water. In winter, the dough becomes too hard, so less salt is used and more water.[4] The difference between summer and winter is 2 grams of salt, which is 0.5 grams per 100 grams of flour. Even so, the fact that the recipe changes by season suggests that the dough's state is influenced by temperature. However, these numbers are just one example for 400 grams and are not a rule that applies to all udon.
5. How Stepping on and Layering the Dough Strengthens It
In school-oriented instructions for handmade udon, 50 cc of water and 1 teaspoon (5 grams) of salt are mixed with 100 grams of flour. The resulting lump is put in a plastic bag, and you step on it using your body weight 100 times. This is repeated 2 to 3 times. The materials state, "The more you step, the more elasticity you get."[5] In professional processes, there is a step called "training." Kagawa Prefecture materials describe making a strong dough by layering it while rolling it up or folding it into thirds.[4] Both stepping and layering seem to be tasks that apply force to align the inside of the dough. The materials provide these procedures and the explanation that elasticity results from them.
6. What Resting the Dough Does to Its Strength and Flavor
The dough is not finished once it is kneaded. In the "Sanuki no Yume" method, after forming balls, the dough is put in a bag and rested for 5 to 10 minutes. This wheat has slightly less gluten, so efforts are needed to bring out koshi.[4] The resting time varies greatly depending on the variety and the shop. Inaniwa udon from Akita is even more special. It is said that the dough is aged multiple times after kneading, re-kneading, and stretching. Over time, the gluten becomes stronger and the dough settles. This method uses hand-kneading rather than stepping with feet.[6] Because Inaniwa uses a special method, this is not a story that applies to all udon. Research from the Saitama Prefectural Industrial Technology Research Center found that as the aging time of udon dough increased, many amino acids and sugars increased. These increased flavor components also affected the boiled noodles.[7] This is a story about flavor, not koshi. What happens inside the dough during resting to make it stretchy cannot be explained here.
7. How to Investigate Udon Texture Further on Your Own
Things you can do today. Eat udon one strand at a time, separating the feeling of smoothness when it enters your mouth from the push-back when you chew. If you have noodles with different boiling times, comparing them makes the differences easier to see. Things you can do when you go out. If there is a noodle shop or a udon-making workshop nearby, you might ask if they change the amount of salt by season when the opportunity arises. You do not have to go out; comparing udon at home is enough. Official information. Sites for Kagawa and Saitama prefectures publish materials on methods and research. The SPring-8 reports are technical, but just looking at the diagrams can show you how gluten research is conducted.