Part 4: All About Kombu
My Love for Kombu
As I mentioned briefly in the introduction, kombu became the star in my kitchen ever since I started using in my daughter’s baby food. When I first started feeding her solid foods, I began by letting her grow accustomed to the soft taste of kombu dashi, then little by little added more variation and flavors into her meals.
My fondness for kombu comes from the fact that it has the most delicate and gentle flavor out of all the other kinds of dashi. While the punch of katsuo dashi and the distinct fragrance of shiitake dashi has its time and place, they cannot compare to the ability of kombu dashi to support and bring out the best in practically all ingredients. Kombu has a unique power to pull out the subtlest of natural flavors and bring them to life through cooking.
Kombu dashi is excellent with cuisines other than Japanese food, as well. For example, you can make a delicious potage-style soup by stewing vegetables with finely sliced pieces of kombu and then blending everything into a smooth soup in the mixer. It is also outstanding for other dishes such as cabbage rolls, pot-au-feu (French-style beef stew) and tomato-based stews which will turn out tasting better by just adding the kombu. The versatility of kombu to pair with and enhance any kind of cooking is truly remarkable.
The Basics of Kombu
The process of turning kelp into the “kombu” used for making dashi is simple. In general, two year old kelp is harvested from the sea, then naturally dried in the sun. It is this shear simplicity that makes kombu all the more profound and interesting to learn about and use.
Kombu is harvested mainly off the coasts starting from Hokkaido and running to the northeastern Tohoku region. One of the the most fascinating things about kombu, is that depending on the exact coastline, ocean currents, ecology of the area and other environmental factors, the characteristics and flavor of the kombu that grows in any particular area can vary immensely. Like katsuo-bushi, if you know the differences between the major types of kombu, you will be able to enjoy it even more in your cooking. There are four major types of kombu that are especially good to know about, which I will explain next.
Known as the “king of kombu,” makombu has the best overall balance of flavor, umami and fragrance. It has a thick, fleshy texture and the tough fibers that give it a stiff body. It is often compared to the similarly textured rishiri kombu (more below about rishiri kombu), but no other type of kombu produces the same unique kind of soft, smooth and well-rounded flavor like makombu.
Makombu is mainly harvested around the southern end of Hokkaido and the region called Minami-Kayabe is especially well-known for producing top quality makombu.
Whenever I do a blind tasting session with different kinds of dashi in my cooking classes, almost everyone votes raus kombu as the dashi with the most umami. Not surprisingly, raus kombu happens to contain the highest amount of glutamates (the source of umami flavor), out of all the types of kombu. Raus kombu is much softer and thinner compared to the other kinds of kombu allowing you to make dashi in a shorter amount of time. Although dashi made with raus kombu tends to give the broth some cloudiness, it is hard to find a comparable substitute for the level of full-bodied flavor it will bring out in your cooking.
Rishiri kombu is what probably comes to mind whenever most people in Japan think of kombu. It gets its name from where it is harvested in the northern part of Hokkaido - around the Rishiri and Rebun Islands, as well as off the coasts of Wakkanai and Teshio. It is characterized by its thick, fleshy blades, stiff fibrous structure and jet black color.
Perhaps Rishiri kombu's most distinctive feature is that it creates an extremely clear dashi broth. This makes it excellent for emphasizing the color and subtle flavors of the ingredients within your dishes, and it is the dashi of choice in most of Kyoto's "kappo" restaurants which serve fine traditional Japanese food.
When it comes to affordability and ease of use, Hidaka kombu is number one. Dashi brewed from Hidaka kombu is great for everyday cooking. Like raus kombu, Hidaka has a soft and thin blade that makes brewing the dashi easier and faster than the thicker types of kombu. Since it becomes quite soft when cooking, it can used as an ingredient in other dishes or even eaten by itself. Hidaka kombu is also the kind of kombu used in oden for musubi kombu, or pieces of kombu tied into the shape of a bow tie or knot and simmered in a flavored broth.
Although it is easy to use, Hidaka kombu is actually not ideal for making dashi because it does not provide much flavor or umami to the stock and tends to make the broth cloudy. Still, other kinds of kombu can get rather pricey, so I find nothing wrong with using inexpensive Hidaka kombu for daily cooking and no fuss meals.
Besides the above kinds of kombu, there are also other kombu products available such as "suki-kombu" (kombu cut into strips) and "kombu-ko" (kombu powder) which are easy to use and great in a variety of dishes. For example, suki-kombu can be rehydrated and used in salads, and kombu-ko can be used to thicken soups or is good sprinkled on pastas. I recommend using suki-kombu and kombu-ko in not just Japanese cooking, but western cuisines as well.
Kombu matures well as it ages so “fresh" is not necessarily the best choice. In fact, kombu that has been aged under ideal conditions continues to develop more and more umami and flavor - there are even highly treasured "vintage kombu" that have matured for two to three years. It is good to know there are both "wild" kombu, that had been harvested from the seas where it grows naturally, and farmed kombu which is grown by producers. Wild kombu is superior in both flavor and aroma. However, it is more expensive as well, so it’s best to consider what kind of kombu to buy based on what you will use it for and of course, what you can afford.
When picking out kombu to buy, I recommend looking for kombu that is thick and has some glossiness to its surface. If you ever have the chance to go to a dried-foods shop where the shopkeepers still let you choose the pieces of kombu you want yourself, you should take the chance to smell all the various types and note their differences. The best quality kombu has no hint of staleness and an aroma that will practically make your mouth water! Avoid any kombu that has a yellowish color or seems unnaturally dark or black in color - this is a good sign that it has not been properly stored.
Kombu can be stored at room temperature without affecting the flavor but you want to make sure to protect it from humidity and moisture. Wrap it in newspaper or similar material and store in a well ventilated place. Since kombu’s flavor improves with age, you can continue to use it even after the expiration date has passed. Properly stored kombu will often develop small, white spots on its surface. This is actually a sign of maturity and good umami development, so by all means do not try to wipe or wash it away before cooking because it will add more flavor to your dashi!
Making Kombu Dashi
One great characteristic of kombu is that there are two methods you can use to draw out the dashi: heating it in hot water or simply letting soak in cold water. Kombu dashi made by soaking in cold water will result in the most refined and clean tasting stock. Since no heat is used, cold soaking gently pulls out the natural flavors of the kombu without bringing out any unpleasant tastes or bitterness. On top of that, all you need to do is drop a piece of kombu in some water, let it sit overnight and you will have a delicious batch of dashi waiting for you to use the next morning. It can’t get much easier than that.
How to make hot kombu dashi
- Use 15 g kombu to 1 liter water. Let the kombu soak in water for at least 30 minutes, but it is better if soaked overnight.
- After soaking, warm the water and kombu on medium heat, letting the temperature rise to about 60°C (140°F). This is the best temperature for drawing out the flavors from the kombu. Once the water reaches temperature, taste the dashi. Keep the temperature steady and let the dashi brew until it reaches the strength and taste you prefer. Do not boil the water or else you risk making the broth cloudy and releasing unpleasant flavors from the kombu.
How to make cold soaked kombu dashi
- Use 15 g kombu to 1 liter water. Submerge kombu in the water and let soak in the refrigerator overnight. Remove kombu and use the liquid for cooking.
Whether you are making hot or cold dashi, here are a few tips to help you ensure you get the best tasting dashi every time:
- Before placing the kombu in water to soak, lightly wipe it with a dry cloth. Some say to wipe it with a moist cloth, but the kombu nowadays is not very dusty or dirty so wiping with a dry cloth will suffice. Washing kombu with a wet cloth will just wipe away the umami that has developed on its surface.
- Some instructions for making kombu dashi will tell you to make cuts into the sides of the kombu pieces, but this is not necessary. The flavors diffuse out of the surface of the kombu so cutting slits into the pieces will not give you anymore flavor.
In the end what really makes kombu the most fascinating to me, is pairing it with other ingredients. Since kombu doesn't assert itself in your dishes like katsuo dashi, kombu dashi goes well with just about any ingredient. I will talk more about pairing the different kinds of dashi in cooking and give specific examples in Part 7: Using Dashi in Cooking, so stay tuned.