With the ever-growing popularity of Asian restaurants in the West also arises the curiosity to learn about their unique, yet most commonly used ingredients. When you think of kombu and nori, you probably think about vegetables that combine flawlessly with your sushi rolls, however, there are some major differences between these two, even though they’re both considered sea vegetables.
So, what’s the difference between them? Technically, kombu is kelp, while nori is seaweed. What sets them apart besides their size, is that kelp grows strictly in saltwater environments and is harvested near rocky ocean coastlines, while seaweed can grow in multiple marine-based environments such as lakes, rivers, and oceans.
Additionally, there are several other differences worth mentioning that range from appearance, texture, nutrition, and culinary usage. In this article, I’ll provide you with a deeper insight into all of these differences.
Major differences between kombu and nori
We have briefly learned that kombu is a species of kelp, while nori is a species of seaweed.
On that same note, seaweed is an umbrella term used to describe numerous marine-based species of plants and algae, while sea kelp describes the largest subgroup of seaweed. Plus, the major difference between these two is that seaweed can grow in any marine environment, while kelp strictly grows in saltwater and is mostly found along rocky coastlines.
Beyond that kombu and nori have several differences, especially in terms of appearance and use.
Appearance and texture
Kombu is sold dry in whole sheets or small pieces based upon your preferences. Unlike Nori, it is very thick and has a dry texture that immediately softens when immersed in water. It also has a very dark color, with some kombu actually being dark-grey.
Nori, on the other hand, is also sold dry in both of the forms we’ve mentioned, but it has a crispy texture, and is lighter in color, especially when compared to kombu. Unlike kombu, nori should never be submerged in water, otherwise, it will ruin its taste and texture.
While kombu and nori are both sea vegetables, they have distinct nutrient profiles, which is perfectly normal considering that potatoes and carrots have different nutrients even though they’re both root vegetables. Therefore, it’s also normal for different species of sea vegetables to have unique macro and micronutrient profiles.
For example, 100 grams of kombu have the following nutrient composition:
- Calories: 16
- Carbs: 3.65 grams
- Fiber: 0.5 grams
- Protein: 0.65 grams
- Fat: 0.21 grams
While 100 grams of nori have the following nutrient composition:
- Calories: 35
- Carbs: 5 grams
- Fiber: 0.3 grams
- Protein: 6 grams
- Fat: 0.3 grams
On a macronutrient level, nori has a superior calorie and protein content (at least according to the information presented in nutritional labels) but it’s not very significant.
What really sets kombu and nori apart, however, is their iodine content.
Kombu has significantly more iodine than nori. The average iodine content in kombu is 2523 mcg per gram (1,682% of the RDI), while the average iodine content in nori is 37 mcg per gram (25% of the RDI). This is very significant because excessive iodine consumption may precipitate hyperthyroidism, hypothyroidism, goiter, and/or thyroid autoimmunity, which means too much kombu might be bad for your health.
Other than that, both kombu and nori have significant levels of vitamins A, B, and C, as well as minerals such as iron, magnesium, potassium, calcium, as well as zinc.
Growth and harvest
Most kombu comes from Hokkaidõ, Japan, but it is also cultivated in Korea, where it is known as dashima, and China, where it is known as haidai. There are three farming methods usually employed to grow kombu, all of which make use of floating rafts and culture ropes with kelp:
- Vertical culture method: This method makes good use of water space and is considered a simple and easily manageable system. However, there is limited sun exposure to meet the requirements for good kelp growth.
- Horizontal culture method: This method is generally applied in shallow waters where turbidity is high, for example, the coastline of southern China. And while it provides the kelp with good sun exposure, the culture ropes may be too exposed to strong currents.
- Mixed culture method: This method combines the vertical and horizontal methods, solving the disadvantages encountered when using either of the other systems. It’s been widely adopted by Laminaria sea farming enterprises in China.
Harvesting kombu is quite labor-intensive since it requires untying the culture rope from the floating raft, loading the kelp into sampans (boats), and transporting it to the seashore for sun-drying or processing.
Japan is also the biggest producer of nori, and just like kombu, three farming methods are commonly employed to cultivate it:
- Floating system: This method has been used in Japan but it’s also been adopted by China. Nets are attached to buoys floating on the surface of the sea so that the nori thalli is constantly soaked in water.
- Semi-floating system: This method is a combination of floating and fixed net systems. At high tide, the nets float on the surface, but when the water level goes down, the nets stand on land.
- Fixed nets: Also referred to as “pole system”, this method consists of nori nets hung between poles. During ebb tides, the nets are exposed to air and become dry. This system ensures that periodic exposure of the proper duration, reducing the incidence of disease and the growth of competitive weed species.
After being nurtured in the open sea for 40 or 50 days, the first harvesting phase begins. Harvesting can last up to 5 months, with an interval of 10-15 days each time, which means the crop is harvested 10-12 times annually. Nori can be harvested manually or with the use of machines, unlike kombu.
Kombu is associated with good fortune in Japanese culture, which is why it’s often served during the new year, as it is believed to bring good fortune for the rest of the year. Kombu can be cooked in a variety of ways, but it’s mostly used to prepare dashi, a popular dish in Japan, by immersing it in boiled water. Kombu is also simmered in mirin, soy sauce, and a variety of other seasonings and added to boiled dishes for extra flavor. It can also be softened in vinegar and shredded to make a dish called Tororo-kombu.
Nori is the most popular of the two. It is commonly used in sushi restaurants to wrap sushi and rice for a variety of dishes, also referred to as norimaki-zushi. This type of dish doesn’t require any preparation and the nori is used in its natural, dry state. It’s a popular breakfast snack when wrapped around rice and dipped in soy sauce. Nori can also be shredded and added to a bowl of rice, or also added to tea, in which case it’s called O-chazuke.
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Other popular types of sea vegetables
Kombu and nori are among the popular types of sea vegetables, but others are considered just as nutritious and versatile in their culinary usage.
Wakame, which is also known as sea mustard in the West is as popular as kombu and nori in Japan. It is a delicate, lightly sweet seaweed often used raw and rehydrated in salads and miso soup. Because of its silky, satiny texture, it’s better to pair wakame with ingredients that have some crunchiness or chewiness. Wakame, like kombu and nori, also has an equally rich mineral and vitamin profile.
Not as popular in the West, hijiki has many uses, including soups and stews, stir-frys, fish dishes, in sauces, and even as a seasoning for salads. It’s rich in dietary fiber, and essential minerals. Its use is associated with health and beauty, and thick, black, lustrous hair is connected to its regular consumption in small amounts. That being said, countries like Canada, United Kingdom, and the United States have advised against its consumption due to containing potentially toxic quantities of inorganic arsenic.
Made from tengusa (a form of plant that is also coined as heavenly grass), kanten is very similar to gelatin, but it’s not made from animal body parts. It is used to make all types of jellies, puddings, and custards. Kanten is semi-translucent and firmer with less jiggle. It is also used to make wagashi (Japanese confectionery) like yokan and anmitsu.
Can kombu go bad?
Kombu is very shelf-stable, but as with any dried food, it should be stored in a dry, dark, and moderately cool place. It can be kept in the pantry for one year before it begins to lose its vaguely sweet, maritime aroma in exchange for a stale, musty one.
Can nori go bad?
If kept unsealed, nori can last up to 2-3 years. In any case, it’s a good idea to search for indications in the packaging. The shelf life of nori may depend on a variety of factors, such as the best by date, the preparation method, and how it is stored. However, as a general rule, opened nori should last about 2-3 weeks, which will also depend on how you store it.
Can eating too much kombu or nori be bad for my health?
Eating too many of these sea vegetables may be dangerous for one reason: iodine. Iodine is an important mineral in our diet, and it plays an important role in regulating thyroid function. However, too much iodine in our system can be toxic as it may trigger problems associated with the thyroid. In fact, excess iodine may sometimes decrease the production of thyroid hormones and cause hypothyroidism.