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This week, we’re talking seaweed… or as we like to call it, sea vegetables.

In Japanese, the word for seaweed is “kaiso”. Kaiso are an important part of the Japanese diet. The Japanese have been harvesting them for thousands of years, both wild and cultivated. Kaiso are highly nutritious (many sea vegetables are especially rich in calcium) and a source of flavor enhancement (naturally occurring glutamates).

Although it’s already passed, did you know that April 14th is Nori Day? In Shibushi, Japan, April 14th is Nori Day to honor the nori industry and Kathleen Drew-Baker, an English botanist whose research in red algae led to breakthroughs in technology that led to large-scale nori cultivation being possible. To the Japanese, she is known as “Mother of the Sea”… a huge honor!

Kombu

Kombu is an extremely important sea vegetable in the Japanese pantry. It is used primarily to make stocks (such as dashi) because of its abundant, naturally occurring glutamates. Kombu is gathered in the shallow waters off Hokkaido, Japan’s northernmost island.

The best variety, rishiri kombu, is 1/8” thick, 5” to 8” wide and grows anywhere from 5’ to 8’ long. When purchased in a specialty shop in Japan, it comes dried in full lengths, or is precut into convenient sizes, which are packed in flat plastic envelopes. It pays to buy the best quality you can find, as its subtle flavor varies widely. However, it might be hard to find the best varieties in the US.

Kombu has virtually no protein, but is high in calcium, carotene, iron and iodine. It is thought to contain cancer-fighting ingredients.

Wakame

Wakame is often used in soups, such as miso soup, or in sunomono salads. It is usually sold in dried form, and soaked in water before using.

Wakame is usually dried or preserved in salt, making it a staple for the Japanese pantry.

To reconstitute dried wakame: soak a small handful (it expands a ton) in a bowl of room temperature water for 10 minutes. Rinse, chop and serve raw in salads, or serve lightly simmered in soup.

Fresh wakame is available during springtime in Japan. Fresh wakame is more delicate than dried wakame and has fabulous flavored.

Wakame is high in fiber, calcium, iron, and vitamins.

Nori

Nori are thin, dried sheets of seaweed that have a crisp texture.

Japan produces more nori, both in quantity and variety, than any other country in the world. The early Japanese ate nori raw, as early as the 7th century.

Today nori is farmed. Spores are planted in January on nets and placed in bays or lagoons. After harvesting the seaweed in autumn, it is washed in cold water and then spread thinly onto sheets to dry in the sun. It is then toasted and cut into sheets, or seasoned with soy sauce and mirin to make flavored nori.

Because sushi has become so popular in the US, it is becoming easier to find nori in grocery stores, sold in 8” x 7” black or dark green sheets. Better quality nori is thick and has a tight and even texture.

Nori is used for making maki zushi, cut into pieces to eat with onigiri, or crumbled over cold soba noodles, seafood domburi, and other dishes.

Furikake nori has small bits of nori in it, as well as other ingredients such as sesame seeds, and is used as a condiment – often sprinkled over rice.

“Korean-style” nori is a popular snack. Approximately 2″x4″, very thin pieces of nori are seasoned with sesame oil and salt, and usually come about 10 to a package. They’re an excellent guilt-free replacement for potato chips. (If you have any sort of Asian supermarket near you, they’ll probably have it. If you have a Costco membership, you can also check your local Costco for them… they’re $6 for a box of 24 packages.)

There’s also a Japanese version of these, which are slimmer (1″x3″) and a little thicker, and come in a variety of flavors.

Nori is high in protein and dietary fiber. It contains high proportions of iodine, carotene, vitamins A, B, and C, as well as significant amounts of calcium and iron.

Keep packages of nori in ziplock bags once opened, as moisture will ruin its texture and crispness.

Hijiki

Hijiki is a brown sea vegetable that grows wild on rocky coastlines around Japan. Fisherman and professional divers harvest hijiki with a sickle during low tide in the spring. After harvesting, the hijiki is boiled and dried. Dried processed hijiki turns black.

Hijiki has been a part of the Japanese diet for centuries. According to Japanese folklore, hijiki aids in health and beauty. Regular consumption of small amounts of hijiki is said to produce thick, black, lustrous hair.

Hijiki is rich in dietary fiber and essential minerals, such as calcium, iron and magnesium.

Dried hijiki expands when reconstituted in room temperature water. It is often chopped very fine and mixed into items such as sushi rice, dips and dressings, and grains. This type of seaweed is not used to wrap sushi, as other seaweeds often are.

Despite the health benefits, hijiki is considered by many to be dangerous for consumption due to high levels of inorganic arsenic naturally present in the seaweed. The Canadian Food Inspection Agency issued a warning about the arsenic in 2001. The Food Standards Agency in Britain followed with a similar warning in 2004. They noted that levels were especially high in the liquid remaining after rehydrating, which is why the Japanese always discard this liquid and then rinse the rehydrated hijiki under cold running water before cooking it. The soaking liquid from hijiki should never be consumed.

Other agencies to issue warnings include the New Zealand Food Safety Authority and the Food and Environmental Hygiene Department in Hong Kong. Inorganic arsenic can be linked to cancer, liver damage, and gastrointestinal problems. the levels of arsenic in hijiki are considered to be toxic. However, Japan’s Ministry of Health, Labor and welfare has pointed out that the average daily intake of hijiki for those in Japan is minimal and therefore unlikely to cause serious damage. The Japanese Ministry of Health and Welfare stated, “There are no records of cases of arsenic poisoning as a result of the arsenic content of sea vegetables.”

Basically, you need to make your own judgment call.

Hijiki should be used in small amounts. One to two tablespoons per serving is usually more than enough to add texture to a dish.

A good use for hijiki is this hijiki summer salad.

Arame

Arame is a type of kelp that is sold dried in long, thin, dark slivers that look a lot like hijiki. Arame has a similar flavor and texture to hijiki, so it makes a good substitute, especially if you are concerned about arsenic in hijiki.

To soften, cover it with warm water and let it soak for 20 to 30 minutes. It will not expand (unlike hijiki), but will become softer to the touch and more pliable. Drain off the liquid and rinse with cold water. Drain again and blot up excess moisture.

Aonori

Literally translated, aonori means “blue seaweed”

Aonori is a type of edible green seaweed that is commercially cultivated in some bay areas in Japan.

Aonori is dried and then used as a flavoring in soups, tempura, etc. Often, it is sprinkled on hot food, like yakisoba, okonomiyaki, takoyaki, miso soup, or on Japanese potato chips. Sometimes it is mixed with salt or used as one of the spices in shichimi togarashi (7-spice seasoning).

It contains minerals such as calcium, magnesium, lithium, vitamins, and amino acids.