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Nori and Karengo Seaweed, What is The Difference?

For many, sushi is our first contact with seaweed as a food. Sushi is made from a versatile seaweed known as ‘Nori’ – the Japanese word that refers to a group of red seaweeds traditionally classified as ‘Porphyra‘ *. There are many different types of porphyra around the world (over 100 different species) and although the word ‘nori’ is the most popular/universal name for this type of seaweed, it is also known as sleabhac, laver, sladai…to name only a few.

In New Zealand, Nori is called Karengo or Parengo and to date, NIWA scientists have identified about 35 species growing along our coasts. Colour, texture and shape may vary according to the individual species. Karengo’s blades (the equivalent of leaves on land plants) can be pink, purple, gold, or greenish and range from huge sheets with the texture of cellophane to long, irregular ribbons. Some are really tough and others are very delicate and tender, but all are just one cell thick – making them unique among seaweeds.

Karengo grows in the inter-tidal area of the seashore, mostly anchored to rocks; at low tide, the plant is exposed to air and the elements for a number of hours every day and then under water at high tide. Research by NIWA on two karengo species at Kaikoura, shows that the blades are able to re-grow from the base after harvesting. For much of the year Karengo cannot be seen easily, it may be only a speck on the rocks. Like other plants, their main growing period is spring. At maturity and from a distance, it may look like a torn black plastic bag melted on the rock.

Visual representation of various species of NZ Karengo, courtesy of Dr Wendy Nelson, NIWA

* To complicate matters, scientists are now discovering that some of the species called porphyra are actually something else (Clymene, Lysithea and Pyropia – most NZ species are Pyropia as are the commercial species in Asia).

The fact remains that they are quite similar when it comes to the taste.

In New Zealand, Karengo is considered taonga by Māori and can be gathered from the wild for personal use. There is only one licence to harvest Karengo commercially, by hand in New Zealand between July and September along a defined stretch of coast in the South Island. Due to the earthquake in 2016, harvesting has currently been stopped to give the seabed time to recover. As a result, Pacific Harvest offers two options – a farmed karengo from Korea or wild karengo from South America. Both are tested for contaminates.

The nutritional profile of Karengo includes relatively high concentrations of protein, calcium, iron, fiber, potassium, magnesium, phosphorous, iodine and vitamins A, B1, B2, C, D, and E. It also contains taurine (which is documented to lower blood cholesterol), no fat and is a good source of Omega-3 fatty acids. It has natural anti-inflammatory, anti-biotic, anti-fungal, antiviral & anti-parasitic effects. Studies are being done on its ability to cure stomach cancer and ulcers.

Nori Cultivation /Farming in Asia

In Asia, virtually all nori is farmed and processed into sheets/wraps in China, Korea and Japan. In much of Asia, nori cultivation is well understood and very productive. Hybrids with superior growth and nutritional characteristics have been developed and patented by large companies.

Nori ‘breeding’ in lab pools
Net structure used in Asia

First the spores are bred and multiplied in lab pools where temperature and light are optimised. Nets are then seeded with the spores and suspended in clean ocean water. As the spores are nourished by nutrients in the water, and the sunlight they grow into increasingly large strands of seaweed. In this system, also known as the “pole system”, the nori nets are hung between poles. At low tides, the nets are exposed to air and become dry. Techniques of floating nets now allow nori cultivation in deeper areas of the sea.

Tying nets to the structure
nori nets under water at high tide
Nets exposed at low tide

After rearing in the open sea for 40 or 50 days (may vary according to species), the first harvesting phase begins. Harvesting activities can last for 5 months. The interval of harvesting is every 10-15 days; therefore, the crop is harvested 10-12 times annually.  The Nori strands are cut from the net and then washed and ground into slurry. The slurry is then fed into a machine which flattens and dries the seaweed into uniform sheets, much like the process of making paper. The Nori sheets are then roasted and graded.

Most nori sheets are also glazed, giving them their shiny surface and salty taste. The glaze can give the sheet a variety of flavours but also serves the purpose of keeping it together; like in sea salt the abundance of minerals in seaweed attracts moisture which may make the wrap more fragile to breaking apart.

Collecting nori in purpose-made boats
Processing nori into sheets
Glazed nori sheets

Although nori farming is the subject of experimentation in other parts of the world (namely the USA and UK), they are not likely to become major producers. In Asia, a large amount of biotechnology work has taken place for decades to hybridise, cross and mutate various indigenous species to improve growth rate, increase resistance to disease and prolong cultivation period. As a result, the knowledge base and farming experience is staggering.

Martin harvesting karengo

In New Zealand karengo is not prepared into sheets/wraps for several reasons. The harvest is very limited and further treatment would make the seaweed un-affordable. Equally important, NZ’s karengo tradition does not use wraps and in this way is more akin to the European ways of using laver.

Karengo has very unique culinary qualities: one of them is that it changes its taste with the way it is used. Soft dried straight out of the bag, it tastes like dried mushrooms or smoked tea – it’s lovely with eggs, potatoes or as a simple snack. When roasted or baked, the flavour is intensified and nutty, it is delicious with nuts & seeds or as a garnish. When moist, the taste is that of mild anchovies, and is a great alternative to the fish in Mediterranean dishes. Pacific Harvest also uses Karengo to make seaweed seasonings (Furikake). Also, you can make your own sushi wraps...using more than nori 🙂

Disclaimer: This material is provided for educational purposes only and IS NOT intended as a substitute for professional medical advice, diagnosis, or treatment. This information is generic and should be verified by a qualified health practitioner for specific & individual needs & requirements.

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