is simmered, smoked and fermented skipjack tuna (Katsuwonus pelamis, sometimes referred to as bonito). It is also known as bonito flakes or broadly as . Shaved katsuobushi and dried kelp—kombu—are the main ingredients of dashi, a broth that forms the basis of many soups (such as miso) and sauces (e.g., soba no tsukejiru) in Japanese cuisine. Katsuobushis distinct umami taste comes from its high inosinic acid content. Traditionally made katsuobushi, known as karebushi, is deliberately fermented with Aspergillus glaucus fungus in order to reduce moisture. Katsuobushi has also been shown to impart kokumi (a term translated as "heartiness"). Traditional production process The fish is beheaded, gutted, and filleted, with the fatty belly, which does not lend well to being preserved, trimmed off. The fillets are then arranged in a basket and simmered just below boiling for an hour to an hour and a half, depending on their size. The rib bones are then removed and the fillets smoked for up to a month using oak, pasania, or castanopsis wood. They are smoked for five to six hours in one session, left to rest one day for the condensation to rise to the surface, then fired and smoked again the next day. This smoking and resting cycle is repeated 12–15 times in total. The built-up tar from the smoke is cleaned from the surface using a grinder. At this stage the fillets are called and most commonly found in stores shaved and packaged for sale under the name or hanakatsuo. They are not true katsuobushi without the last fermentation stage, but still valued as a good substitute. The last stage of creating katsuobushi is to allow the fish to sun-dry using the assistance of mold. The fillets are sprayed with Aspergillus glaucus culture and left for two weeks in a closed cultivation room. The mold ferments the fillets and also draws out any residual moisture. The mold is continually scraped off, with further sun-drying increasing hardness and dryness until the fillet resembles a piece of wood, with less than 20% of its original weight. By definition, only fillets that have been treated in this manner may be referred to as katsuobushi. After repeating this process of mold growth and sun-drying at least twice, the katsuobushi can also be called , and fillets repeating this process more than three times can be called . When tapped together lightly, they sound almost metallic,