Nori is the Japanese name for edible seaweed (a "sea vegetable") species of the red algae genus Pyropia, including P. yezoensis and P. tenera. It has a strong and distinctive flavor. It is used chiefly in Japanese cuisine as an ingredient to wrap rolls of sushi or onigiri, in which case the term refers to the dried sheets. The finished dried sheets are made by a shredding and rack-drying process that resembles papermaking. They are sold in packs in grocery stores for culinary purposes. Since nori sheets easily absorb water from the air and degrade, a desiccant is needed when storing nori for any significant time.
Nori is commonly used as a wrap for sushi and onigiri. It is also a garnish or flavoring in noodle preparations and soups. It is most typically toasted prior to consumption (yaki-nori). A common secondary product is toasted and flavored nori (ajitsuke-nori), in which a flavoring mixture (variable, but typically soy sauce, sugar, sake, mirin, and seasonings) is applied in combination with the toasting process. It is also eaten by making it into a soy sauce-flavored paste, nori no tsukudani. Nori is sometimes also used as a form of food decoration. A related product, prepared from the unrelated green algae Monostroma and Enteromorpha, is called aonori, literally blue/green nori) and is used like herbs on everyday meals, such as okonomiyaki and yakisoba.
Production and processing of nori is an advanced form of agriculture. The biology of Pyropia, although complicated, is well understood, and this knowledge is used to control the production process. Farming takes place in the sea where the Pyropia plants grow attached to nets suspended at the sea surface and where the farmers operate from boats. The plants grow rapidly, requiring about 45 days from "seeding" until the first harvest. Multiple harvests can be taken from a single seeding, typically at about ten-day intervals. Harvesting is accomplished using mechanical harvesters of a variety of configurations. Processing of raw product is mostly accomplished by highly automated machines that accurately duplicate traditional manual processing steps, but with much improved efficiency and consistency. The final product is a paper-thin, black, dried sheet of approximately 18 cm 20 cm (7 in ?? 8 in) and 3 grams (0.11 oz) in weight. Several grades of nori are available in the United States. The most common, and least expensive, grades are imported from China, costing about six cents per sheet. At the high end, ranging up to 90 cents per sheet, are "delicate shin-nori" (nori from the first of the year's several harvests) cultivated in Ariake Sea, off the island of Kyushu in Japan. In Japan, over 600 square kilometres (230 sq mi) of coastal waters are given to producing 350,000 tonnes (340,000 long tons) of nori, worth over a billion dollars. China produces about a third of this amount.