Kombu is edible brown kelp dried into thick, stiff, dark sheets — the foundational ingredient of Japanese cooking, where it is steeped to make dashi, the clear savoury stock that underpins miso soup, simmered dishes and countless sauces. Exceptionally rich in free glutamate, kombu is the seaweed that, in 1908, led the chemist Kikunae Ikeda to isolate glutamic acid and name the fifth basic taste, umami. Beyond stock it is simmered into sweet-soy tsukudani, slow-cooked in oden, knotted into musubi-kombu and tucked under steaming rice.