Naturally made snow-dried kanten is available in bars and flakes in most natural foods stores. The Mizoguchi family's kanten is sold in the United States under the Emerald Cove, Erewhon, Mitoku Macrobiotic, Sound Sea Vegetables, and Tree of Life labels. A powdered variety is often sold in Oriental foods stores, but this type is usually made by a chemical process that is used in large factories. Read labels carefully and look for the words "snow-dried."
According to Peter and Montse Bradford, authors of Cooking With Sea Vegetables, the jelling ability of natural kanten varies according to the acidity or alkalinity of the food with which it is used. Acidic foods may require more kanten than alkaline foods do. Testing the recipe is recommended by taking a spoonful of the heated mixture and allowing it to rapidly set on a cool surface. If the mixture does not set in a few minutes, add a little more kanten to the pot and simmer a few more minutes.
To use kanten bars, tear them into several pieces and soak them in water for thirty to sixty minutes. Remove the kanten, squeeze out any excess water, and place in a saucepan along with the liquid called for in the recipe. The liquid should be cold or at room temperature. Bring to a simmer over medium heat without stirring. Once the liquid begins to simmer, stir occasionally until the kanten dissolves (about two to three minutes).
Prepackaged flakes need not be soaked. Simply sprinkle the measured amount over the liquid before heating and proceed as instructed for kanten bars. In any recipe, flakes can be substituted for bars and vice versa. The jelling strength of one bar of kanten is equal to two slightly rounded tablespoons of flakes.