Even though potatoes may seem a little uninspiring, they are probably the most striking illustration of the meaning of umami in European peasant cuisine. The taste of cooked potatoes owes much to the umami substances glutamate and guanylate, which are released during cooking. In fact, the free glutamate content of a potato doubles when it is cooked. A cooked potato has practically no aroma, and it is not possible to simulate its taste by combining sour, sweet, salty, and bitter tastes.
Cooked potatoes are often found in dishes that are rich in umami, such as the braised potatoes in cassoulet or in red flannel hash. A dash of Worcestershire sauce or soy sauce adds some extra umami to the potatoes. The water from boiled potatoes can be recycled to advantage for making dashi or gravy.