The cell membranes of fresh raw vegetables are semi-permeable membranes that allow water to pass through but impede the passage of other substances. When this is immersed in water, water penetrates through the cell membrane, but the substances inside cannot escape. Water moves from the thin side to the dark side so that the concentration of substances inside and outside the cell becomes equal. (Become crunchy)
In other words, the purpose of soaking shredded vegetables in water is to improve the texture of the vegetables. In addition, cold water (ice water) is used because the cells themselves soften when the temperature is high.
Even if the tissue is immersed in water to give it tension, if it takes too long and the water absorption reaches its limit, nutrients such as vitamin C will conversely dissolve from the tissue into the water.
When shredded cabbage with a width of 2 mm is soaked in water for 30 minutes, the residual vitamin C rate is 77%. In other words, 23% escapes, but it is up to each person to decide whether to take this as too much or too little.
In theory, to make them more crunchy, boil the vegetables at 50-60°C and then immerse them in ice water.