Kombu is the Japanese word for dried sea kelp. In China it is called Haidai.
Kombu/Kelp/Haidai, are large seaweeds (algae) belonging to the brown algae (Phaeophyceae) in the order Laminariales. There are about 30 different genera* around the world (see Laminariales for more information). Kelps grow in underwater “forests” in shallow oceans. They require nutrient-rich water with temperatures between 6 and 14 °C (43 and 57 °F) and are known for their astronomical growth rate.
Kelp grows around the world in cold waters. Various species proliferate in different places, according to the climate, currents and exposure. In New Zealand, we have several different kelps, the ones that are best known include Bull Kelp (Durvillia), Macrocytis kelp (or South Island Kelp) and Ecklonia Kelp (or North Island kelp). Kombu is known to us from its important role in the Japanese cuisine and is also eaten in other parts of Asia. The exact type of kelp made into kombu (naturally dried) may vary according to location – in Japan, for instance, the ‘Saccharina japonica’ kelp is the most plentiful, therefore that is what the Japanese use. All of the parts of the plant are used, including the thick stalks and fronds (leaves in seaweed vocabulary).
Kelp is highly prized not only for its abundance of essential minerals, vitamins, and trace elements but also for its natural glutamic salts: a naturally sweet, superior flavor enhancer which creates the famous savory “fifth taste” (umami) in Japanese cuisine. When dried naturally, kelp acquires a thin layer of white powder which some consumers believe is extremely flavourful. This white powder is not mold, but is actually the amino acid glutamine. When preparing kombu, this powder should not be washed away, but if there is any foreign material the strip can simply be wiped clean with a slightly dampened cloth. Kombu left exposed to air will become damp (like sea salt, the high quality minerals attract moisture) and its flavour will be lessened; it is therefore recommended to keep it in an air tight container. Damp kombu can be dried again under the sun or in a very low temperature oven (<50 C) to bring back its crispy texture.
On the health side, the white powder ‘Glutamine’ is one of the 20 amino acids encoded by the standard genetic code. It is not recognized as an essential amino acid but may become important in certain situations, like intensive athletic training or certain gastrointestinal disorders. It is also said to be a superb brain fuel, and some people refer to it as a “smart-vitamin” – although it is in actual fact not a vitamin at all.
Japan has a tradition of eating kombu that goes back for several centuries. Traditional Okinawan cuisine relies heavily on kombu as a part of the diet; in fact, Okinawa uses more kombu per household than any other prefecture. Japan had a plentiful supply of kelp in its natural sea beds on Hokkaido. The naturally growing plants are biennial and harvesting used to occur from boats between the months of June and October. Hooks of various types are attached to long poles and used to twist and break the seaweed from the rocky bottom. As demand grew in the 1960s, attempts were made to develop artificial cultivation methods, but the two-year cycle meant the costs were too high. In the 1970s, forced cultivation was introduced, reducing the cultivation period to one year, similar to the system developed in China in the early 1950s. A lot of the kombu on the market is from the species Saccharina japonica, which grows abundantly around the Japanese coast. More recently, it is extensively cultivated on ropes in the seas of Japan and Korea. Over 90% of Japanese kombu is cultivated.
Since the 1960s, dried kombu has been exported from Japan to many countries. It was initially available only at specialised Asian food shops and restaurants, but has now become widely available in many specialty grocers. Previously China imported Kombu from Japan & Korea, but now China also cultivates Kelp on a large scale (information from FAO).
Many different types of kelp can be used to make Kombu, and its preparation is very simple. In Japan, the whole seaweed is washed thoroughly with seawater, cut into 1 m lengths, folded and dried. The same process is used in New Zealand to prepare Pacific Harvest’s kelp, only it is then milled into granules to be used as a seasoning. The small granules become soft when exposed to the moisture on food and look like cracked pepper. These granules can be used easily to make dashi just the same; just fill a tea ball with the kelp granules and follow the recipe below.
Kombu/kelp is one of the three main ingredients needed to make dashi, a soup stock used in a multitude of Japanese dishes. Making dashi is simple: a strip of dried kombu (or a teaball filled with kelp granules) is placed in cold water , then heated to near-boiling; then the flakes of dried smoked bonito, a type of tuna, are added. The softened kombu is sometimes eaten after cooking. Ingestion of the seaweed is recommended because of the detoxifying properties of its fibre.
A small piece of kombu/kelp granules added to dried beans helps to tenderize them as they cook. (Click the link to find out more.)
In 2010 a group of researchers at the University of Newcastle found that a fibrous material in sea kelp (called alginate) was better at preventing fat absorption than most over-the-counter slimming treatments in laboratory trials. As a food additive it may be used to reduce fat absorption and thus obesity. Kombu/kelp contains very little calories and is a popular diet food. It contains the most potassium of all the sea vegetables. Because potassium removes sodium, it is effective at improving swelling. Kelp contains fucoidan, a type of polysaccharide known to activate the liver cells. It is said to also be effective in cleaning the blood and decreasing cholesterol levels. Find out more about kelp’s benefits by following the link.
* Genera is a phyto-taxonomy (plant nomenclature & classification) term for ‘families’ which contain many ‘genus’ which themselves have many varieties. As an example, Pacific Harvest’s kelp is Ecklonia radiata: Class= Brown seaweed or Phaeophyceae, Order= Laminariales (kelps), Genera/Family= Alariaceae, Genus= Ecklonia and Specie= radiata.