Mozuku (Nemacystus decipiens) (モズク)

Mozuku (Nemacystus decipiens) is marine alga classified under the family Spermatochnaceae or the family Chordariaceae in the order Chordariales, the class Phaeophyceae. They are branched filamentous algae. Mozuku is written as "藻付く" meaning "algae attach" in Chinese characters.

In Japan, Nemacystus decipiens, a kind of the family Spermatochnaceae, is called as Japanese name mozuku (another name, ito-mozuku), but the family Spermatochnaceae has many kinds.

It is tens of centimeters in length, but is only one to a few millimeters in width, and branches in every point.
It secretes polysaccharide on the surface and slimy when you touch

It is mainly distributed over shallow seas in the Tropical and Temperate zones. In the Japanese coast, mozuku grows on the shore reef lit by sunlight in the infralittoral zone during the winter and spring, but in the summer, it dies like other marine algae. It is said that mozuku was named after "藻付く" meaning "alga attaches" because it attaches to other Phaeophyceae such as hondawara (Sargassum fulvellum). Okinawa mozuku (Cladosiphon okamuranus) does not attach to brown algae, but attaches to rocks directly.


Mozuku (Nemacystus decipiens) is taken for food in Japan. Strictly speaking, over 90 percent of the mozuku distributed for food within Japan are Okinawa mozuku (Cladosiphon okamuranus) and ishi-mozuku (Sphaerotrichia divaricata) belonging to the family Chordariaceae. Mozuku (Nemacystus decipiens) belonging to the family Spermatochnaceae is rare.

Within Japan, Okinawa Prefecture and outside Japan, the Kingdom of Tonga, are especially famous for main production areas. In Taiwan, Okinawa mozuku (Cladosiphon okamuranus) is tried to be cultured as a substitute for facai (Nostoc), and is named as "Sea Facai" for a trade name.

"Mozuku su", mozuku seaweed salad with vinegar soy sauce dressing, or "shiokara", salted mozuku seaweed, are common cooking for mozuku as an ingredient. Mozuku contained in the plastic container with tosazu (vinegar flavored with bonito shavings, konbu kelp, sugar and soy sauce) or sanbaizu (vinegar, soy sauce and mirin (or sugar) mixed in roughly equal proportions) is ready-to-eat food and is mainly sold. Fresh mozuku (or salted mozuku after removing salt fully) is used for Tempura which is fried with coating of batter, suimono (clear soup), or rice gruel. In Okinawa Prefecture, special Tempura with thick coating of batter is made from mozuku and is dipped in sauce (seasoning) to eat.

Mozuku is brown when it grows in the ocean, but it turns to be green like other brown algae when you branch it in boiling water. It has a texture like wakame seaweed when you have a bite, but you first feel a slimy texture caused by the polysaccharide on the surface.


Sliminess - Polysaccharide (dietary fiber)
Fucoidan - Fucose
Algin acid
Carotenoid - Fucoxanthin (a kind of Vitamin A)
Arachidonic acid (an essential fatty acid, a kind of Vitamin F)
Vitamin C
Vitamin K
Eicosapentaenoic acid (EPA)
Amino acid - Glycine
Inorganic compound - Magnesium, Calcium, Potassium, Phosphorus, Sodium, Iron

[Original Japanese]