Sold in health food stores, Asian markets and specialty online retailers, dried seaweed is more readily available and convenient than fresh. Most, but not all, dried seaweeds need to be rehydrated before you use them in a recipe. The simplicity of the process, which usually takes minutes, is a good reason to expand your sea vegetable repertoire beyond sushi wrappings.
Dried Seaweed Varieties
The most commonly eaten types of seaweed include nori, kombu, wakame, hijiki, arame and dulse. You can also find bags of mixed types of dried seaweed. Not all types need to be rehydrated. Nori, sold in thin, flat sheets, is ready to eat or use for sushi right out of the bag. Dulse can be cooked or eaten raw, and does not need to be rehydrated beforehand. Most other types of dried seaweed need to be rehydrated. If you are in doubt, read the directions on the package.
Nori and laver are different names for the same type of seaweed. Nori generally refers to the thin, rectangular sheets used for sushi making or toasting as a snack. It doesn't need to be rehydrated. Laver, on the other hand, is sold dried but otherwise unprocessed, and does need to be rehydrated before use.
How to Rehydrate
The rehydration process for dried seaweed is a simple one--soak the seaweed in water until it's tender. The ideal soaking time and water temperature vary depending on the variety, as well as the thickness, of the individual pieces. For the best results, follow the directions on the packaging or in your recipe. Otherwise, rehydrate dried seaweed as follows:
Rinse the seaweed under cold running water. If the pieces are small, place them in a colander first.
Fill a bowl with more than enough water to cover the seaweed. Cold water is usually sufficient.
Submerge the rinsed seaweed in the bowl of water. Leave it to soak for five to 10 minutes, or the time recommended on the packaging. You should see the seaweed expand, and the color might brighten.
Most types of dried seaweed will rehydrate in five to 10 minutes. Soak it for closer to five minutes to retain a little bite, or 10 minutes if you like it to be more tender.
Some types of seaweed need longer than 10 minutes to rehydrate. Laver, for example, might need as long as an hour. The best way to test whether the seaweed has soaked for long enough is by tasting a piece.
Remove the rehydrated seaweed from the bowl and squeeze out the excess water. Use a colander or squeeze the seaweed in a clean kitchen towel.
Transfer the seaweed to a chopping board and slice it into pieces using a sharp knife or with kitchen scissors. Some seaweed varieties, such as alaria, or wild Atlantic wakame, have a thick rib down the center of the leaves that remains tough even after rehydration. You may want to cut away and discard this rib.
Some recipes require you to steam or simmer dried seaweed or soak it in hot water to rehydrate it. Pickling and marinating dried seaweed also has a rehydration effect. The seaweed will soak up the vinegar or marinade instead of water, resulting in an intense flavor. In braised dishes that include seaweed, add the dried seaweed directly to the dish for the final hour or so of cooking time.
Kombu and Dashi
Kombu, a thick type of kelp, is used to make dashi, a broth that's an essential component of miso soup. Making dashi involves rehydrating dried kombu by simmering it in water, then keeping the water and discarding -- or eating -- the kombu. Add bonito flakes, strain and you have dashi, an umami-rich broth with a taste reminiscent of the ocean.
What to Do With Rehydrated Seaweed
- Toss rehydrated seaweed with raw vegetables, sesame seeds and a light, citrusy dressing to make a seaweed salad.
- Add it to soups, such as miso and minestrone, for an umami boost.
- Throw some into a stir-fry near the end of the cooking time.
- Chop it finely and include it in veggie or bean burger mixtures.
- Saute rehydrated seaweed with olive oil and garlic to serve as a simple side dish.