The waters surrounding Japan are abundant with sea vegetation. Indeed, all manner of marine plants have historically been an important source of food for people across the archipelago. Some sea vegetables require little in the way of processing — just rinsing and drying after harvesting — while others are rendered deliciously edible only after considerable effort. Kanten (agar) gelatin is certainly one of the more ingeniously crafted foodstuffs sourced from the ocean.
A red marine algae called tengusa (literally “heavenly grass”) is dried and boiled to make a nearly colorless, very stiff aspic called tokoroten. Although tengusa’s ability to gel has been known and utilized in many Asian cuisines for centuries, the Japanese claim kanten as one of their contributions to the culinary world.
Sometime in the late 17th century, a new kind of tokoroten began appearing at Japanese tables.