Nori seaweed is the most common edible seaweed produced worldwide. An eye-catching deep purple sushi rolls you must have seen in any Japanese restaurants is actually the red nori algae that grows proficiently in the intertidal sea zones in many temperate areas around the world.
Scientific name: Prophyra spp., Rhodophyceae.
The characteristic red colour of these algae results from excessive amounts of phycoerythrin pigment which outstrips the other pigments like phytocyanin, chlorophyll-A, β-carotene and a number of photosynthetic biliproteins (phycobilins).
|Raw nori seaweed with kombu.
(Photo courtesy: Simon Huntley)
Nori is the Japanese name for purplish lever. Japan, the Republic of Korea and China are the chief commercial producers of this seaweed. Nori features a very thin, flat, purplish blade and therefore, preferred in sushi rolls.
Porphyra species commercially grown in seaweed farms where shore emerges above sea water during low tides, and submerges under the water at high tides. The ropes arranged in the ocean in such a way that they are allowed come out of water and expose to air for a few hours a day. The Porphyra spores germinate on the ropes and grow into new thallus (blade).
Each brownish red thallus (frond) composed of one-cell layer of flat, broad, elliptical blades which generally grow up to 15-20 cm long.
Raw, wet Porphyra thus collected either by hand or using machines is further processed into dried sheets of nori in the processing units. During processing, most salt is washed away, so that the sodium content of prepared nori is low.
Dried and cut sheets are packed in bundles and dispatched to the markets for sale. Simple, dried, un-toasted product is called hoshi-nori, which distinguishes it from yaki-nori, which is toasted.
Nori tops the list of seaweeds with the healthiest nutrition profile. It holds just 35 calories per 100 grams.
It composes sugars and fats in low percentages, but has high contents of minerals, and vitamins, with significant amounts of vitamins A, vitamin C, B-complex groups; and minerals like iodine, manganese, phosporous, and iron.
It is among the most nutritious seaweeds with easily-digestible and bio-available protein content ranging from 10-15 percent.
Nori and other red algae carry ample amounts of vitamin-A. 100 g of fresh, raw nori contains astoundingly 5,202 IU or 1734 % of daily recommeneded levels of vitamin A. Further, vitamin-A is required for maintaining healthy mucosa and skin and is essential for night vision. Consumption of natural vegetables and fruits rich in vitamin-A and flavonoids are also known to help the body protect from lung and oral cancers.
Laver (red algae) also contains good amounts of many B-complex vitamins such as vitamin-B6 (pyridoxine)-12% of RDA, riboflavin-34% of RDA, folates-39% of RDA, thiamin, and niacin. Folates in the diet help prevent neural tube defects in the newborns.
100 g of fresh nori seaweed has 39 mg or 65% of daily recommended levels of vitamin-C. However, drying and toasting greatly reduces its shelf-life. Vitamin-C is a powerful antioxidant, which helps the body develop resistance against infectious agents and scavenge harmful oxygen-free radicals.
It is also an important vegetable source of EPA (20:5 n-3, eicosapantonoic acid), a omega-3 fatty acid.
The characteristic flavor of nori seaweed is attributed to the large amounts of three amino acids: alanine, glutamic acid and glycine.
|Principle||Nutrient Value||Percentage of RDA|
|Total Fat||0.28 g||1%|
|Dietary Fiber||0.3 g||1%|
|EPA (20:5 n-3)||0.080 g||--|
Ready to use, dried nori sheets are available in the Japanese stores and supermarkets all around the year. Choose sheets that are shiny and having a firm, dry, brittle in texture, and green hue when exposed to the bright light. Both hoshi-nori (dried, un-toasted) and yaki-nori (dried and toasted) sheets in sealed packs put for the sale in these markets.
Store nori sheets in cool dry place at home away from moisture and humidity. Keep nori flakes and powder in sealed containers.
Nori seaweed sheets are the cornerstone of sushi bars. This purplish-red seaweed turns green when dried and toasted. Nori usually employed as tasted and little moistened sheets in these popular sushi bars to wrap around cooked rice. Nori features strong fishy (amine) flavor.
Here are some serving ideas:
|Sushi rolls layered with nori sheets
Photo courtesy: Rusty clark
Nori sheets are used to prepare sushi. It is wrapped around the cooked (venegar) rice with a slice of common vegetable, raw shrimp or fish.
Nori egg soup (Nori tamago sumashijiru) is a popular Japanese clear soup served before dinner as an appetizer. It is sprinkled over cooked rice, vegetables and seafood.
Furikake is a Japanese condiment mixture of dried fish, nori, sesame seeds, suagr and salt.
Nori flakes alone also spinkled as garnish in vegetable, chicken, and salmon salads.
Nori crusted salmon is another popular dish in which nori powder is sprinkled over salmon fillet and grilled in oven.
Crumbled nori sheets used in bread, sandwiches, fish, tofu, vegetable, pasta dishes and rice. It is also used as a condiment and an infusion.
Nori seaweed, being a marine produce, carries relatively higher concentrations of minerals, trace elements and heavy metals. Dried nori carries less mineral content than fresh, wet harvest seaweeds. Iodine content in dried sheets may range from 16-20 μg/g in nori. People with known thyroid disease (thyrotoxicosis- excess thyroxin hormone production in the body) may want avoid seaweeds in their diet for the same reason. Its moderate conumption, on the other hand, offers several health benefits which otherwise may not found in other plant-based diets. (Medical disclaimer).
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Further reading (Links opens in new window):
Fisheries and Aquaculture Department-A guide to the seaweed industry.