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{{Short description|Dried, fermented, and smoked skipjack tuna}}
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| serving_size = 100 g
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[[File:Shitake and Bonito shavings at Yakitoro in Madrid.webm|thumb|Steam animates ''katsuobushi'']]
[[File:Katsuobushi 3.jpg|thumb|A bag of ''katsuobushi'' flakes]]
{{nihongo|'''Katsuobushi'''|{{linktext|鰹節}}|lead=yes}} is [[simmered]], [[Smoked fish|smoked]]  and [[Fermented fish|fermented]] [[skipjack tuna]] (''Katsuwonus pelamis'', sometimes referred to as [[bonito]]). It is also known as '''bonito flakes''' or broadly as {{nihongo4||おかか|'''okaka'''}}.

Shaved ''katsuobushi'' and dried [[kelp]]—''[[kombu]]''—are the main ingredients of ''[[dashi]]'', a broth that forms the basis of many soups (such as [[miso soup|miso]]) and sauces (e.g., ''[[soba]] no tsukejiru'') in [[Japanese cuisine]].

''Katsuobushi''{{'}}s 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 ''[[Taste#Heartiness|kokumi]]'' (a term translated as "heartiness").<ref>{{cite book|author1=Mikiharu Doi|editor1-last=Toko|editor1-first=Kiyoshi|title=Biochemical sensors: mimicking gustatory and olfactory senses| chapter= 8: Investigation into the Kokumi Taste of Soup Stock Materials|date=2013|publisher=Pan Stanford |location=Singapore |isbn=978-9814267076|page=123 |ref=kokumi}}</ref>

==Traditional production process==
[[Image:Katsuobushi block.JPG|thumb|''Katsuobushi'' is in wood-like blocks.]]
The fish is beheaded, gutted, and [[fish fillet|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. At this point, the fish is dry and hard, and the built-up tar from the smoke and excess fat is cleaned from the surface using a grinder.<ref>{{cite AV media |title=かつお節ができるまで。カツオの街から生まれたかつお節。 |url=https://www.youtube.com/watch?v=2OcV0IHbtCM |access-date=2023-09-09 |language=ja |minutes=18 |script-quote=ja:削り作業 節の外形を整えることと、焙乾中に表面ににじみ出た脂肪分を除き、 カビがむらなく付き易くするためです。 |trans-quote=The trimming work is to shape the exterior of the fish block and to remove the fat that surfaces during drying, preventing uneven mold formation.}}</ref>  At this stage the fillets are called ''{{nihongo4||荒節|arabushi}}'' and most commonly found in stores shaved and packaged for sale under the name ''{{nihongo4||鰹削り節|katsuo-kezuri-bushi}}'' 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 [[food drying|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 {{nihongo4||枯節|karebushi|"dried fillet"}}, and fillets repeating this process more than three times can be called {{nihongo4||本枯節|honkarebushi|"true dried fillet"}}. When tapped together lightly, they sound almost metallic, and unlike their dull beige outer appearance, when broken open they are a translucent deep ruby color inside. Rarely, very high-end ''honkarebushi'' repeat this drying process for over two years.<ref>{{cite web|title=Katsuobushi Museum|url=http://www.daiyan.jp/makeing.html|access-date=23 February 2012|url-status=dead|archive-url=https://web.archive.org/web/20120127215253/http://www.daiyan.jp/makeing.html|archive-date=27 January 2012}}</ref>

In the Edo era, it was common for ''katsuobushi'' to go through an extra step, the so-called {{nihongo4|tebiyama style|手火山式|tebiyama-shiki}} process. After the fillets are boiled and their rib bones removed the fish are put in steaming baskets stacked atop one another for one to two hours a few meters above a burning wood fire.  These are rotated to assure an equal exposure to the smoke. The result is more flavorful and resistant to deterioration. Due to the extra cost and facilities required only a few factories following ''tebiyama-shiki'' remain.

== Shaving ==
[[Image:Katsuobushi kezuriki.jpg|thumb|right|[[Katsuobushi kezuriki]] used to prepare ''katsuobushi'' shavings]]
Traditionally, chunks of ''katsuobushi'' were shaved as needed with an instrument similar to a [[Plane (tool)|wood plane]] called a ''[[katsuobushi kezuriki]]''.
[[File:Numazu Gyosho Tokaido.jpg|thumb|[[Hiroshige]]]]
Today ''katsuobushi'' is typically sold in bags of small pink-brown shavings, which vary by thickness: smaller, thinner shavings, called ''hanakatsuo'' ({{lang|ja|花鰹}}), are used as a flavoring and topping for many Japanese dishes, such as [[okonomiyaki]], while the larger thicker, called ''kezurikatsuo'' ({{lang|ja|削り鰹}}), are favored for making the widely used dashi stock.

==Uses==
In addition to making dashi, other popular uses of ''katsuobushi'' include:
* Okaka, finely chopped ''katsuobushi'' dressed with soy sauce.
** As a stuffing for rice balls (''[[onigiri]]'').
** As a topping for rice. Popular for [[bentō]], often covered with [[nori|strips of laver]].
** Dried okaka is used as an ingredient of ''[[furikake]]'' rice topping (called "okaka furikake").
* As a seasoning for cold [[tofu]] (''[[hiyayakko]]'', {{lang|ja|冷奴}}) along with grated [[ginger]] and [[Welsh onion]] (a type of [[spring onion]]).
* Sprinkled with [[sesame]] seeds and chopped [[nori|laver]] atop cold soba noodles ([[soba|zarusoba]]).
* As a topping on [[takoyaki]], [[okonomiyaki]] or [[agedashi dōfu]].
* As a seasoning on [[century egg]] along with [[sesame oil]] and [[soy sauce]].
* As a high-protein treat for [[cat]]s sold at pet stores.
* As a topping for ramen mixed with salt.<ref>{{cite web|url=http://www.souschef.co.uk/bureau-of-taste/ramen-flavour-bomb-katsuobushi-salt/|title=Ramen Flavour Bomb: Katsuobushi Salt|date=7 August 2018 }}</ref>

== Health ==
The [[mycotoxin]] [[beta-nitropropionic acid]] has been found on ''katsuobushi'' as well as in [[miso]] and in [[soy sauce]], two other Japanese fungal fermented products. Certain strains of ''A. glaucus'' are reported to produce mycotoxins.<ref>{{Cite book|chapter-url=https://books.google.com/books?id=9xlIicZfQ5IC&q=mycotoxins+katsuobushi%7C&pg=PA7|title=Advances in Food Mycology|isbn=9780387283913|editor=Ailsa Diane Hocking|first1=Jens C.|last1=Frisvad|first2=Ulf|last2=Thrane|first3=Robert A.|last3=Samson|first4=John I.|last4=Pitt|date=2006-08-29|chapter=Important Mycotoxins and the Fungi which Produce Them<!--|section=2.5 ''Aspergillus'' Toxins: β-Nitropropionic Acid (BNP)-->|page=7|series=Advances in Experimental Medicine and Biology|volume=571|publisher=Springer Science+Business Media, Inc.|location=New York}}</ref>

Due to the smoking process which involves tar and charcoal, amounts of [[benzopyrene]] exceeding EU standards, as much as 37μg per kilogram, have been detected in commercially sold ''katsuobushi''.<ref>{{Cite book|url=https://books.google.com/books?id=xCUSBQAAQBAJ|title=Chemical Induction of Cancer: Structural Bases and Biological Mechanisms|last1=Arcos|first1=Joseph C.|last2=Argus|first2=Mary F.|date=2013-10-22|publisher=Elsevier|isbn=9781483263731|language=en}}</ref> As a result, they have been banned for sale in the European Union.<ref>{{Cite web|url=http://www.japancrush.com/2014/stories/anger-over-eu-import-ban-on-bonito-flakes-over-carcinogen-issue.html|title=Anger Over EU Import Ban On Bonito Flakes Over Carcinogen Issue|website=japanCRUSH|language=en-US|access-date=2016-04-14}}</ref>

==See also==
{{portal|Food}}
* [[List of dried foods]]
* [[Maldives fish]]

==References==
{{reflist}}

==External links==
{{Commons category|Katsuobushi}}
{{Cookbook|Bonito Flakes|l1=Bonito flakes}}
* [http://www.katsuobushi-jp.net/types_productionmethods.php Katsuobushi types and production methods]
* {{Cite web |last=Angela |first=Berg |date=2019-10-24 |title=Katsuobushi – traditional production |url=https://en.tellerrandstories.de/manufacture-katsuobushi/ |access-date=2022-11-25 |website=Tellerrand-Stories}}

{{Japanese food and drink}}
{{Dried fish}}
{{Authority control}}

[[Category:Japanese condiments]]
[[Category:Dried fish]]
[[Category:Fermented fish]]
[[Category:Smoked fish]]
[[Category:Umami enhancers]]
[[Category:Toppings]]