The fresh mushrooms themselves don't have that much water. It's all the water that's soaked in later to increase the portion size. Normal maitake mushrooms don't have too much odor, and if you refrigerate them for a few days, they usually don't go bad as far as how much of the root is cut. If it is a fresh fresh mushroom cut off the root impurities can be. If it is an older mushroom. You should cut more aging roots.