Nori (Dried laver seaweed)


Nori that is seeded in autumn grows during winter. The young shoots that are first harvested from November to December are called Hatsushiomono or Hatsunori. It is soft and is made into the most premium product. However, nowadays it is mostly grown and harvested through aquaculture. Therefore, the seeding is divided into 3 to 4 batches during the winter so the young shoots can be harvested as many times. Nori picking peaks February and ends in April. When shipped as product, it is divided into 7 ranks according to color, luster, fragrance, shape, thickness, dryness, and whether or not it is mixed.

Products that are black and have a uniform thickness are considered to be good quality. However, blackness is a matter of preference, and just because it is black doesn’t always mean the flavor is good. But, the Nori that has turned purple does so because it has taken in too much moisture and light after pressing, so it is of poor quality. It is cultivated all over Japan and although production is increasing, it cannot meet demand. Therefore, it is also imported from China and South Korea. Products from Saga, Kyushu have a good reputation, and some of them have a high wholesale price of US $1 or more per sheet (about 3 g).

Nori has a long history in Japan and was mentioned as a tribute to the Imperial Court in the Taiho Code enacted in 701. Nori was reserved for aristocrats until well into the Edo Period when it started to gain popularity and become more available to the general public. This coincided with the beginning of active cultivation of Nori and at the same time, a Norimaki craze, which led to a widespread increase in Nori consumption. At that time, a large volume of natural seaweed was harvested in the Asakusa area, so it was given the name Asakusa Nori. It is also said that the products from the Urayasu and Omori areas were pressed in Asakusa, where there was paper-pressing technology.

Nori is also used for nigiri sushi because it could be found in Edomae. Edomae sushi rolls are thin rolls made with grilled Nori and are called Nori-maki. They are called “gun rolls” (teppo-maki) because of their shape. It is a big difference from the thick rolls made with seaweed that is not grilled in Kansai. Edomae sushi rolls are made with seaweed that is baked and taut, so it requires a great deal of training to learn how to make them.

Nori turns bright green when baked, increasing its aroma and giving it a crisp texture. About 80 to 90% of seaweed shops in Toyosu Market sell grilled seaweed. Even then it is grilled at the sushi restaurant before use and particular attention is given to a strong fragrance.


Etymology of Nori (海苔)

They say that “Nura” which means “slimy” was said with an accent, resulting in the word “Nori”. Records in the year 689 include the word “紫菜献上” in which “紫菜” was read “Nori” (and the entire phrase means “Nori Presentation”).

Nori size

The basic size of seaweed is 21 cm in length and 19 cm in width per sheet, and each sheet weighs about 3 g. This size is called “Zenkei”.

Front and back sides of Nori

The smooth side is the front and the rough side is the back. The back side is rough from the marks of the Nori screen used when the pulpy Nori is pressed. When making rice balls (omusubi/onigiri) or sushi rolls, make sure that the rough back surface is the side that comes in contact with the rice. This means that the front side will be rolled on the outside and provide a smooth taste as well as a shiny and beautiful finish.

Differences in Nori color

Some seaweed color is close to black, some have a reddish tinge, and each product has a different color. These color differences are due to the pigment contained in the seaweed. It is a mixture of the four pigment colors of green chlorophyll, orange carotenoid, crimson phycoerythrin, and indigo phycocyanin.

The color of seaweed changes depending on the differences in the content of these four types of pigments. When the nutritional condition is good, and the young shoots contain a well-balanced abundance of each of the four kinds of pigments, the color of the seaweed is close to black. On the other hand, when grown in an undernourished environment, or when the pigmentation has waned in old shoots, this may make the color brighter and even appear yellowish. In addition, the color of seaweed becomes closer to green when baked, which is another change that is related to the pigment. Crimson and indigo pigments are sensitive to heat and are decomposed by grilling, reducing their content. The content of green and orange pigments does not change significantly even with grilling, so that’s why it turns to a beautiful green color with grilling.


Types of Nori (Laver)

Seaweed is broadly categorized as red algae, which includes black laver, green algae, which includes green laver, and brown algae, which includes kelp and wakame seaweed. Asakusa nori, Susabi nori, etc. are in the red algae category. Hitoegusa and similar are in the green algae category. In Japan, seaweed belonging to the Porphyra genus is used as the raw ingredients for a dried and baked laver. There are 29 species of Porphyra seaweed that have been confirmed on Japan’s coastlines. Of those 29, the following five species are used the most.


Asakusa nori (Porphyra tenera)

This laver was once harvested in the Edomae sea (Tokyo Bay), and was dubbed “Asakusa nori” by the laver researcher, Kintaro Okamura, in 1909. It grows to a width of 10 cm and a length of around 50 cm. For many years it was the main, farmed seaweed of Japan, but once Nawate susabino nori appeared on the market, the level of production of Asakusa nori decreased and now it has become an endangered species. Laver made with Asakusa nori has a red tint when dried, but baking it transforms it into a beautiful green color. The texture of Asakusa nori is soft and smooth in the mouth compared to the firm Susabi nori.


Susabi nori (Porphyra yezoensis)

Originally, this species grew a lot from the Tohoku region to Hokkaido. It grows quickly compared to Asakusa nori, and since the finished product is a nice, black color, it very quickly took the nation by storm. Nawate susabino nori, which grows up to 1 meter in length, was discovered among the farmed Susabi nori. Currently, at least 90% of farmed seaweed is said to be a strain of Nawate susabino nori. The color of laver made from Susabi nori is dark and the closer to black it is, the more expensive it. It has a firmer texture with a glossy luster than Asakusa nori does, and it gives sushi a nice finish.


Suzi aonori (Ulva prolifera)

This laver grows on the coastlines and brackish waters where freshwater flows, throughout Japan. It is shaped in a 1 mm thick tube and is a bright green color. A high volume of branches grows from the thicker part, which is equivalent to the main shaft. It grows to be 20 to 80 cm in length. Sometimes it can even reach 2 meters or more. It is the most expensive green nori. Suzi aonori is a famous product of Shimanto River in Kochi prefecture and Yoshino River in Tokushima prefecture, where it is mass-farmed.


Hitoegusa (Monostroma nitidum)

This laver is named for its single-layer cell structure. The leaves are a bright green color, the membrane is soft and it grows to be about 10 to 15 cm. Hitoegusa spores are attached to a net to be farmed in mid-September, then harvested between December and May of the following year. The main area of production is Mie prefecture. Some are shipped raw, the products that will become ingredients in miso soup, etc., are almost all used as raw ingredients for tsukudani (preservable food boiled down in soy sauce).


Uppurui nori (Porphyra pseudolinearis)

The name “uppurui” comes from the fact that the Uppurui area of Izumo city, Shimane prefecture, has been the main location of production since long ago.

Uppurui nori is the representative species of the “iwa nori” (wild-harvested seaweed). Iwa nori only refers to seaweed growing in the wild in rocky areas, and farmed seaweed cannot legally be sold as “iwa nori” in Japan.


Laver Nutrition

About 36% of laver is dietary fiber. Furthermore, this dietary fiber is water-soluble, so you can expect it to be effective in relieving constipation. It also decreases the absorption of fat and sugar and controls increases in blood pressure and blood sugar levels. Laver is rich in protein and is even called the “soybean of the sea”. It contains about 40 g protein per 100 g, which is far higher than other seaweeds like kelp (about 9 g protein per 100 g) and wakame seaweed (about 2 g protein per 100 g). However, the content is not consistent, and may range from 30 to 55% depending on differences in the production site and the harvest timing. Laver that is brought out of the sea, dried, then repeatedly returned to the sea in the shallows, is high in protein. 

Nori contains 8 of the 9 Essential amino acids, all except for lysine. It has long been known as “sweet seaweed”. When chewed and tasted thoroughly, it is sweeter than other Nori. This is because it contains large amounts of aspartic acid, alanine, glutamic acid, glycine, and taurine, the free amino acids that give Nori its umami, sweetness and richness. In particular, there are high amounts of taurine at 1000 mg per 100 g of dry weight. This is about the same content level as fish and is known to have various physiological benefits such as improvement of liver function. Inside the cells and the walls of the cells of seaweed have about a 45% content of fibrous and sticky storage polysaccharides. Porphyran accounts for 30% of these, and the polysaccharides and oligosaccharides provide benefits such as lowering blood cholesterol, lowering blood pressure, antimutagenic and antitumor effects. Therefore, it is thought that continuous ingestion on a daily basis has positive effects on health maintenance and the various illnesses known as llifestyle diseases. As for vitamins, 100 g of Nori contains about 3 times the vitamin A as 100 g of eel, about twice as much vitamin C as 100 g of eel, 1.5 times the vitamin B1 as 100 g of pork and eel, and about 7 times the vitamin B2 as 100 g of chicken eggs and eel. One sheet of Nori contains about 3/4 of the daily recommended intake of vitamin B12 for an adult. It is not well known that Nori has a much higher vitamin content than foods that are considered to be high in these vitamins.

In addition, Nori condenses and accumulates all minerals present in seawater. Minerals that present in especially large volumes in Nori include potassium, phsophorus, calcium, magnesium, sodium, iron, folate (one sheet of Nori contains approximately 1/4 the recommended intake for an adult), iodine (one sheet of Nori contains approximately 2/3 the recommended intake for an adult), etc., but there are also many small amounts of other essential minerals so it is an excellent food source.

Although laver is rich in nutrients, because its cell walls are thick, the digestion rate of these nutrients is only about 50%. The rest is excreted without being digested. Then, the protein in the laver is processed by the digestive enzyme, pepsin and becomes Nolipeptide in its completely digested state, which is effective in lowering blood pressure. In addition, a component called Porphyran* is found among the carbohydrates in the laver, and this has sin moisturizing effects.

So why does laver have so many functions that isn’t found in other seaweeds?

Kelp and wakame seaweed grow their entire lives in the sea, but laver lives in harsh environments where it is exposed to low tide, so it is equipped with biological defense in order to protect itself from drying out and ultraviolet rays. Also, Porphyra 334**, extracted from laver, is also used in beauty products, such as shampoo, as a natural component derived from seaweed.

*Porphyran: The mechanism to protect laver from withering and drying out, even when left in the sun at low tide, is a sulfated polysaccharide substance unique to laver called Porphyran. Like hyaluronic acid, it has water retention capabilities, so it is used as an ingredient in cosmetics.

**Porphyra 334: A substance that absorbs UVA and protects the living body. The UVA blocking function doesn’t exist in brown algae such as wakame seaweed, or green algae such as aonori, but exists in even higher volumes in laver than in other red algae.


This section explains the trick to roasting nori (seaweed).

Grilling with bicho charcoal (high-grade charcoal produced from ubame oak) gives seaweed a wonderful aroma and flavor. Bicho charcoal doesn’t flame up, but the heat is strong. The trick is to just let it gently touch the net of the furnace, and quickly turn it over so that it doesn’t burn. It’s not easy to know when to turn it over at first, it takes some getting used to. If you sweep it over the heat, kind of like a broom, it won’t be heated evenly and part of it will burn. Instead of trying to grill it perfectly to 100%, it’s actually better to stop at about 90%, making sure it’s even through to all four corners. This gives the seaweed a vivid color and gives off a nice aroma. Using normal charcoal would cause flames, and the seaweed could catch on fire, and using gas causes moisture. The heat is too weak with electric appliances, so it takes a lot of time to grill. Bicho charcoal is hands-down the best way for roasting seaweed. It makes the seaweed crispy and melts in your mouth.


What is Non-acid-treated Nori?

The Nori currently sold in Japan is said to be mostly acid-treated Nori. Acid treatment is the process of adding malic acid or citric acid into the sea where seaweed is growing in order to prevent deterioration of the quality of the Nori. Doing this prevents the quality from degrading. Foods that have not undergone acid-treatment are known as “organic” and it can be said they don’t use excessive chemicals. Nori is a suitable food for Japanese people, not just people who are ill or have a poor intestinal environment, but Nori without acid-treatment is recommended for those with allergies or hives.


Japan’s four major Nori producing areas and their characteristics

Ariake Sea

Saga, Fukuoka, Kumamoto and Nagasaki prefectures, which sit on the Ariake Sea, are production sites and Saga especially is the top producer of Nori in Japan. Nori from the Ariake Sea accounts for about 40% of domestic seaweed in Japan. It has a soft texture and as well as a crispiness and also has a sweet and umami flavor.

Seto Inland Sea

Seto Inland Sea is the second largest production site of seaweed after the Ariake Sea, accounting for about 35% of domestic production. The water in the Seto Inland Sea has a high temperature so the harvest season is a little later than in other regions. The seaweed grown in fast tides is dark in color and has a firm and thick texture, giving it a chewy finish.

Ise Bay

Aichi prefecture produces about 8% of domestic product while Mie prefecture produces about 5%. The seaweed produced in the fast-tide Ise Bay is characterized by its crisp texture and strong flavor.

Tokyo Bay

The main harvesting ground for Tokyo Bay is Chiba prefecture. The aroma is said to be the best in Japan the credibility of the distributors is so strong that some wholesalers call Nori from other prefectures “bachi” (meaning from other places). Nori from Tokyo Bay has an excellent aroma compared to other production areas and is also used in sushi restaurants.


Two overseas production sites and their characteristics

South Korea

Nori is a comfort food in South Korea, which produces nearly 13 billion sheets of seaweed annually, and has an annual consumption of seaweed per capita that is higher than Japan. The mainstream flavor is seasoning with sesame oil and salt, and it has a crispy texture. Of the foreign seaweed imported to Japan, the largest amount is from South Korea. In recent years, more than 1 billion sheets have been imported annually, and the import volume is increasing each year.


In China, Nori is cultivated in Jiangsu and Shandong Provinces, and the annual production is over 5 billion sheets. It is not only consumed in China but also exported overseas and in recent years Japan also imports more than 500 million sheets of Nori from China annually.


What nori are preferred by famous sushi restaurants?

Sushi chefs should consult with their nori suppliers, as the flavor will vary depending on the conditions of the year. For example, for Kanpyo maki (dried gourd shaving rolls), choose nori with a strong aroma of the sea and a little thickness, while for Gunkan maki, choose nori with a softer leafy texture. It is necessary to identify the right type of nori for each.

Maruyama-nori-ten (丸山海苔店)

It was founded in 1854. It is used by professionals at 3,000 restaurants in the Kanto area in response to numerous requests regarding the production area, grilling method, color, gloss and texture that the chefs are particular about. It is especially used by many Michelin Star sushi restaurants.

Sushi restaurants like Sawada (さわ田), Sushi Saito (鮨さいとう), Sushi Yoshitake (鮨よしたけ), Sushi Kimura (すし 喜邑), Sushi Takamitsu (鮨 尚充), Nishiazabu Taku (西麻布 拓), Nishiazabu Sushi Shin (西麻布 鮨 真), Kurosaki (くろ﨑), Kiraku (鮨処 喜楽) and Sushi Keita (鮨 桂太) purchase nori seaweed from this store.

Marushin-shouten (丸進商店)

Sushi restaurants like Sushi Izumi (寿司いずみ) purchase nori seaweed from this store.

Kaneko-nori-ten (金子海苔店)

Sushi restaurants like Irifune Sushi (入船寿司: stopping business) purchase nori seaweed from this store.

Marutomo-nori-ten (丸友海苔店)

Sushi restaurants like Sukiyabashi jiro (すきやばし次郎) and Shinbashi Shimizu (新ばし しみづ) purchase nori seaweed from this store.

Inoue-nori-ten (井上海苔店)

Sushi restaurants like Hatsune Sushi (初音鮨) purchase nori seaweed from this store.

Yamamoto-nori-ten (山本海苔店)

Sushi restaurants like Betenyamamiyako Sushi (弁天山美家古寿司) purchase nori seaweed from this store.

Yoshida-shoten (吉田商店)

Sushi restaurants like Ginza Kyubey (銀座 久兵衛) purchase nori seaweed from this store.



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