The most common form of dashi is a simple broth or fish stock made by heating water containing kombu (edible kelp) and kezurikatsuo (shavings of katsuobushi – preserved, fermented skipjack tuna or cheaper bonito) to near-boiling, then straining the resultant liquid. If bonito is not available, dried anchovies or sardines may be substituted. The element of umami, one of the five basic tastes, is introduced into dashi from the use of katsuobushi and kombu. Katsuobushi is especially high in sodium inosinate and kombu is especially high in glutamic acids; both combined create a synergy of umami.
Homemade dashi, made from dried kombu and katsuobushi, is less popular today, even in Japan. Granulated or liquid instant dashi replaced the homemade product in the second half of the 20th century. Compared to the taste of homemade dashi, instant dashi tends to have a stronger, less subtle flavor, due to the use of chemical flavor enhancers—glutamates and ribonucleotides.