Marine Botany

Porphyra Human Consumption

    Why do we eat it??  nori on bamboo

    Have you ever wondered why we eat nori? Why this certain algae? The consumption of Porphyra dates back to 533-544 AD in China. It was even presented annually to the emperor of China during the Sung dynasty (960-1279 AD) as a gift from the Fuijan province. One of the reasons for eating Porphyra is the lack of cellulose in the cell wall, making the algae easier for us to eat and digest.

  1. What sort of nutritive value does nori have?

    Porphyra contains significant amounts of protein, vitamins and minerals. The vitamin C content of nori, or prepared Porphyra, is greater than in raw oranges. The vitamin A content is comparable to that spinach, along with fairly high amounts of vitamin B in general. The amount of free and proteinaceous amino acids in nori are roughly similar to that of vegetables. Porphyra also contains a high amount of arginine, a basic amino acid which is generally found in animal protein. In nori, the characteristic taste is a result of the coexistence of relatively large amounts of alanine, glutamic acid and glycine. It also contains an abundant amount of taurine which is know to be effective for liver activity, especially in preventing the occurence of gallstone disease and for controlling blood cholesterol levels. Nori also contain relatively high amounts of essential trace elements, such as zinc, which is essential for certain enzyme functions. Manganese, copper and selenium are present in Porphyra and essential for the metabolic processes of organisms.

    How is Porphyra consumed?

    tekka maki or tuna roll Nori has always been a staple in the diet of most Asian countries, such as China and Japan. Once collected, nori is washed in freshwater to get rid of the sediments, finely chopped, and spread on frames to dry. Often, nori is toasted and flavored for use in cooking. It is often sprinkled over rice as a flavoring, or used in sushi!

    Besides Asian cultures, others have also utilized Porphyra as a food. In Ireland and the Wales, Porphyra is called laver and can be prepared by frying it in fat or as a pinkish jelly, which can be prepared by heating the fronds in a saucepan with minimal water and beating with a fork.

    Does Porphyra have any medicinal uses?

    Porphyra does have a few medicinal benefits. It contains a sulfated polysaccharide called porphyran, which is a complex galactan. The physiological activity of porphyran in the animal body isn't clear right now, but studies have indicated some excellent health benefits from it. It may inhibit the growth of certain tumors. Also, when nori powder was mixed with a basic diet at 2% concentration and fed to rats, it preventd a purposely induced carcinogenesis. These results may be have been caused by the sulfation of the polysaccharide, which can enhance the effectiveness of it.

    Another substance called porphyosin has been isolated from Porphyra. It appears to exhibit anti-ulcer activity in shay ulcers. However, porphyosin was found to be ineffective against stress ulcers.

    How is Porphyra cultivated?

    The cultivation of Porphyra originates back as far as 300 years ago, when the Japanese utilized a primitve method of using a bundle of bamboo twigs to collect the spores. However, the presence of spores were still at the mercy of nature and annual production flunctuated greatly.

    In China, the cultivation of Porphyra dates back to about 200 years ago, when it was pulled right off rocks in early autumn. This was done right before the release of spores so that the spores would have an area for attachment and growth.

    Modern cultivation of Porphyra did not occur until the 1960's, as a result of the discovery of the Conchocelis phase of Porphyra. The discovery of the Conchocelis phase allowed scientists to determine how to maximize nori production under controlled conditions, leading to one of the biggest industries in Japan and China.

    Which types do we eat?

    In China and Japan, there are 7 main species used in commercial cultivation.

    • Porphyra yezoensis
    • Porphyra tenera
    • Porphyra haitanensis
    • Porphyra pseudolinearis
    • Prophyra kunideai
    • Porphyra arasaki
    • Porphyra seriata

| Intro to Porphyra | Taxonomy | Morphology| Chemistry | Life History |
Human Consumption | Mariculture |

© 1999 Lisa Chen. All rights reserved. Use for educational purposes permitted with acknowledgment and notice.  

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