Kombu is edible kelp, a type of seaweed, and it’s responsible for umami in many Japanese recipes including as dashi (Japanese soup stock), sushi rice, and hot pot.
Kombu (昆布 konbu) is edible kelp, a type of seaweed, widely consumed in East Asia. Known for its excellent source of glutamic acid, an amino acid responsible for umami, kombu plays an indispensable role in Japanese food culture. It grows in the cold currents, and for that reason, 90-95% of kombu is harvested in the winter around the island of Hokkaido(北海道), Japan.
How Kombu is Used in Japanese Cooking
Kombu is hard to digest on its own and must be cooked for a long time before eating. Therefore, it is mostly valued for its depth of flavor – Umami.
This edible kelp is used extensively in Japanese cooking and here are some examples:
The primary usage for kombu is to make Japanese soup stock called Kombu Dashi, which is the base of miso soup, noodle soup, and many other simmered and hot pot dishes. The seaweed is reconstituted by soaking or heating gently in water (it should not be boiled). Sometimes, katsuobushi (bonito flakes) is added to the kombu dashi for more flavor and this is called Awase Dashi, the most commonly used Dashi.
Kombu is also used to wrap around raw fish or vegetables in order to impart its flavor onto the ingredient. This technique is called Kobujime (昆布締め).
Kombu is also eaten as tsukudani (佃煮), a dish where the seaweed is simmered for a long time in a sweet soy sauce-based broth until it absorbs all the flavors and becomes edible. Here’s my Kombu Tsukudani (Simmered Kombu) recipe.
Tsukemono – Japanese Pickles
Small strips of kombu are often included in pickling for additional umami flavor.
Kombu is pickled in vinegar and eaten as a snack called Su Kombu (酢昆布) or eaten as a dried shred (Boro Kombu or Shiraga Kombu).
Different Types of Kombu
There are different types of kombu in Japan. Each type has slightly different flavors and textures. Ideally, it’s best to use a specific type of kombu for each recipe that requires certain taste and texture. Here’s a quick rundown:
- Ma Kombu (真昆布) – thick and wide
- Rishiri Kombu (利尻昆布) – thin and very hard
- Hidaka Kombu (日高昆布) – greenish blackish color
- Rausu Kombu (羅臼昆布) – thin and really wide
1. Ma Kombu 真昆布
Characteristics: 1 to 8 meters in length, 12 to 30 centimeters in width. Light brown color. The thick and wide wedge shape is formed at the bottom that connects to the stem. Popular in Osaka area.
Broth Taste: Refined, sweet, and clear broth
Suitable Dishes: Dashi, clear soup, simmered dishes, hot pot dishes, tsukudani, shio kombu, and tororo komobu.
2. Rishiri Kombu 利尻昆布
Characteristics: Narrower and harder than Ma Kombu. The base of the leaf is a thin wedge. More or less ruffled on the margins. The color is dark brown and the leaves are hard. It is commonly used in Kyoto’s kaiseki meals.
Broth Taste: Strong, aromatic, a little salty, and clear broth.
Suitable Dishes: Great for dashi and soups including Hot Tofu (Yudofu). Great for pickling vegetables (used in Senmaizuke in Kyoto).
3. Hidaka Kombu 日高昆布
Characteristics: 2 to 7 meters in length, 6-15 centimeters in width. Dark greenish and blackish color. Tender and easy to cook, and flexible once rehydrated. Slightly more affordable in price. It is widely used in Tokyo and Northern Japan area.
Broth Taste: It’s easy to cook Hidaka Kombu, therefore, it is used in a variety of kombu dishes.
4. Rausu Kombu 羅臼昆布
Characteristics: 1.5 to 3 meters in length, 20 to 30 centimeters in width. Thin and really wide kombu.
Broth Taste: Rich, soft, fragrant, yellowish, and thick broth. Because of its exquisite taste, it is called “the king of (kombu) dashi.”
Suitable Dishes: Great for kombu dashi, simmered dishes (nimono), hot pot dishes, non-clear soups, and Mentsuyu. Rausu kombu doesn’t have much flavor after being cooked, so it’s not meant for tsukudani or for eating.
Where to Buy Kombu
Kombu is sold in plastic packages as dry strips. It comes with a thin layer of whitish substance on the surface and this is what gives the umami. Never wipe off or wash the kombu.
You can purchase kombu at Japanese and Asian (Korean/Chinese) grocery stores. Whole Foods and natural food stores also carry kombu in the Asian food aisle. Alternatively, you can buy good quality kombu from here that ships internationally.
A reader Jessica recommended this Atlantic Holdfast Seaweed Company in Maine that sells different types of seaweeds.
Note: You might see a Prop 65 warning label on the kombu product. Kombu doesn’t cause cancer specifically; however, seaweeds (kombu, nori, hijiki, etc) grown in Japan are harvested in water that contains higher traces of heavy metals than seaweeds harvested elsewhere in the world. Some health agencies have issued warnings against consuming hijiki specifically, which contains a higher amount of inorganic arsenic than other kombu. But there is no ban anywhere in the world against hijiki or any other kind of seaweed. All kombu contain traces of organic arsenic, but not in quantities that can hurt you, unless you consume more than the usual amount of kombu every single day. Companies are required to put a Prop 65 warning label on their products in California.
How To Store Kombu
I store my kombu in an airtight container (I use this OXO container) in my pantry. It’s important to keep it in a dry, cool, dark place. You can keep kombu for a year. If you have older kombu, check the kombu to see if they is any mold growth. If it looks perfectly fine, you may be able to use it as long as it’s less than 2 years old.
Worth A Read: Seaweed Farming & The Current Trends in the US
In the most recent years, there has been a growing number of fishermen, scientists and consumers in the west, particularly in the US, are seeing kelp and kelp farming as a solution to many environmental affairs. Once an exotic ingredient to the Americans, kombu kelp is starting to be accepted in the US as a promising source of food, jobs and help cleaning ocean waters.
Health Benefits of Kombu Kelp
In addition to flavoring dishes, it’s worth noting that kombu and many other seaweeds are rich in antioxidants, omega-3 fatty acids, iron, calcium, and fiber.
To learn more about the surprising health benefits, read Discover Seaweed: The Essential Ingredient of the Japanese Diet.
Kombu for Vegetarian & Vegan Cooking
As it joins the rank of a superfood, many vegetarians and vegans are starting to incorporate kombu kelp and other seaweeds in their cooking.
Did you know the amino acids found in kombu can help to break down heavy starches in food like dried beans? This has allowed easy digestion and helps minimize the gas-producing effects beans may have. It is especially great news for vegetarians and vegans as beans are one of the main food groups for the diet.
Recipes Using Kombu
From soup stock, sauces, stews, to vegetable dishes, kombu can be enjoyed in a myriad of ways. You’ll value its appeal once you start cooking with this sea vegetable. Here are some recipes featuring kombu for you to get started:
Kombucha / Kobucha 昆布茶
Japanese Ingredient Substitution: If you want to look for substitutes for Japanese condiments and ingredients, click here.
Editor’s Note: The post was originally published in July 2013. The images and content have been updated in April 2019.