Seaweed Stock : Konbu Dashi
Konbu is the most important ingredient in making all Japanese dashi stocks. It also creates a powerful dashi stock of its own and, also, a very nutritious one because konbu is loaded with iodine, iron, calcium, and other trace minerals, as well as the vitamins A and C. In the Setouchi, a simple konbu dashi is the stock most commonly used in cooking. This is primarily because its pure, subtle richness takes a back seat to the delicate flavors of the Setouchi’s seafoods and fresh, seasonal vegetables and complements the region’s light, quick cooking techniques. In addition, many, if not most, Setouchi dishes include some type of fish, shellfish, or mollusk. The glutamate in konbu combines with the isonate form of umami found in these seafoods to create a synergistic effect, exponentially multiplying the umami richness of the dish.
There are three main types of konbu used to make konbu dashi. The same recipe and methods are used to prepare all of them, with each variety producing a dashi stock that has different flavor characteristics. Go here to learn more about them.
Seaweed Stock
Konbu Dashi : 昆布出汁
Makes 4 Cups (1 liter)
Main Foods
Konbu (Dried Kelp), 0.5 oz ≈ 6” piece (15 g ≈ 15 cm piece)
Directions
They are two ways to make konbu dashi. Both are very easy and result in nearly the same flavor characteristics. The cold method produces a slightly more subtle, sophisticated taste. The hot method is more aromatic and slightly stronger tasting. Which you chose largely depends on how much time you have.
Before you begin, there are two optional prep steps you can apply:
Konbu can have some dust and dirt on it from being laid out in the open to dry, and you may want to quickly run the konbu under cold water and then gently wipe it with a damp cloth. But be careful not to wipe off the chalky white substance on the konbu, which gives the konbu much of its umami flavor. For fear of doing this and because most packaged konbu nowadays is largely dust and dirt free, just lightly rinse, not wipe, the konbu.
Cut shallow incisions along the edges of the konbu using scissors. This helps to extract its umam flavori. If you plan to cut the konbu up into strips for another use after it’s been cooked, stagger the width of the incisions with this in mind.
Cold Method:
Put the konbu in a sealable bottle or other type of container with 4 cups (1 liter) of cold water and let it soak for 8 hours or overnight in the refrigerator, up to a maximum of 10 hours. The konbu will double or more in size, and depending on the shape of the container, you may need to cut the konbu in half before you begin. Once it’s ready, take the konbu out, discard it, or save it for another use.
Hot Method:
Put the konbu in a saucepan with 4 cups (1 liter) of water and let it soak for 30 minutes in summer and 90 minutes in winter. (If using Rishiri-Konbu, which is a tougher konbu than the others when dried, it needs to be soaked for 60 minutes.)
Turn the heat on to medium-low and slowly bring the stock to a gentle simmer, about 10 minutes. As soon as small bubbles form around the edge of the konbu, take it out, discard it, or save it for another use. If you’d like to be precise, the ideal temperature for when to take the konbu out is 140F (60C). It’s important to remove the konbu before the stock boils as this will cause it to become sticky and release strong and off-flavors.
Konbu dashi made by either method will keep in the refrigerator for about 3 days and in the freezer for 2 weeks.
Note
You can adjust the strength of the konbu dashi, depending on your taste preference and the dish you’re using it for, by decreasing or increasing the amount of konbu used.