Glutamates naturally found in food deliver a big punch of umami, a sense of savoriness often called the "fifth taste." Seaweed is loaded with glutamate – indeed it was from a seaweed, from kombu, that monosodium glutamate or MSG was created back in 1908.
As noted in my Good Eating story, "Unlocking umami: Foods high in glutamates offer sought-after flavor," you can find glutamates in tomatoes, mushrooms, fish, meat, hard cheese and, yes, seaweed.
Kombu is used to make dashi, the ubiquitous stock of Japan. But you don’t have to use dashi only in Japanese foods; dashi works to give a flavorful boost to most any type of cooking. Stir into sauces, use as a soup base, even deglaze the skillet with it.
American consumers encounter kombu in dried form at Asian markets and some supermarkets. Elizabeth Andoh, the Japanese food authority, offers these tips for buying and using kombu.
-- Most kombu sold for stock making in the United States is either ma kombu or Hidaka kombu. Ma kombu is "broad, fairly thick, flat slices with a slightly grayish sometimes greenish tint,’’ Andoh writes in an email. “Hidaka is narrower, usually appears scrunched up (not flat when dried in the package) and darker, almost black."
-- "All variety of dried kelp will have varying amounts of whitish, chalky powdery film on the surface, this is glutamic acid and should not be wipes or washed away," Andoh cautions.
-- Dashi is made by infusing water with kombu. "Room temperature is the best temperature to do an initial extraction of the flavor-enhancing substance in all kombu," Andoh writes. "Heat can be applied, to good purpose, after the initial extraction, but does not need to be in order to unlock the glutamic acid."
-- Too much heat, such as boiling, will bring on the tannins in kombu, making for harsher flavor, Andoh says. Too much heat will also turn the stock cloudy.
And here’s Andoh’s recipe for making a basic stock using kombu. The recipe makes about 4 cups.
"The master stock used in making traditional vegetarian Japanese cookery is made just from kombu, a sweet but sturdy kelp," Andoh writes in her cookbook, "Kansha: Celebrating Japan's Vegan and Vegetarian Traditions."
Basic kelp stock (kombu dashi)
1 piece kombu, about 1 1/2 by 4 inches if using Hidaka kombu or a 3-inch square ma kombu
4 cups water
1. Place the kombu in a large glass jar. Pour in the water and cover with a lid or plastic wrap. To extract the most flavor, allow the kombu to sit submerged in the water at room temperature for at least 30 minutes or up to 12 hours before using the stock. If you prefer to refrigerate the stock from the start, allow the kombu to soak for at least 8 hours or up to 48 hours before using the stock. Remove the softened kombu from the jar after the flavor is extracted. The stock may be kept, refrigerated, for 4 to 5 days before using.