Katsuobushi – traditional production

It all starts with blood, water and fire. In the end, an ancient process that originated more than 1,500 years ago turns the small tuna species bonito into a rock-hard delicacy. Katsuobushi, known to us as bonito flakes, is the basic seasoning of Japanese cuisine and adds depth of flavor to broths, sauces and soups. Yasuhisa Seriwaza represents the fifth generation of Kanesa Bonito Manufactory. He is not only a producer using old traditional methods, but also a networker. He seeks publicity, goes to fairs and organizes events to tell about the old traditions and production methods. Serizawa is president of Slow Food Mount Fuji and aims to preserve traditional tastes.

Die Manufaktur von Yasuhisa Serizawa ist eine der letzten in Japan, die den Bonito auf dem Weg zum besonders hochwertigen Honkare-Katsuobushi unterzieht. Das geschieht in einem traditionell sehr aufwändigen sechsmonatigen Verarbeitungsprozess / © Foto: Georg Berg
Yasuhisa Serizawa’s manufactory is one of the last in Japan to subject bonito to katsuobushi on its way to becoming a particularly high-quality honkare. Here, Yasuhisa Serizawa shows food journalist Angela Berg the final product after the traditional six-month processing procedure / © Photo: Georg Berg

Archaic force in a family business

On this Monday in September, we witness how the process from fish to flake begins. It has been going on in this place for 138 years and five generations. Yasuhisa Serizawa’s factory is inconspicuously located in a bend on the way down to Tago Bay in the west of the Izu peninsula with its bizarre rock formations. Two tons of tuna are delivered in the late afternoon. The fish are frozen and poured into three large basins to thaw. Outside, the sultriness of the day has subsided and the temperature is perfect for the fish to be ready for processing the next morning.

Am Strand der Tago Bay bringen sich abends unzählige Sonnenuntergangs-Fotografen in Stellung und warten auf den Augenblick, in dem sich der Sonnenball für einen kurzen Moment wie ein Edelstein in die natürliche und runde Aussparung der Felsen schiebt / © Foto: Georg Berg
On Tago Bay beach, countless sunset photographers pose in the evening / © Photo: Georg Berg

Cocktail fans and sunset photographers drive carelessly past the manufactory toward the beach. There is a bar there that only opens for the sunset spectacle. Countless photographers get into position and wait for the moment when the ball of the sun slides into the natural and round recess of the rocks for a brief moment like a precious stone. Admittedly, this expectation is not fulfilled today. The natural spectacle – as old as the earth itself – is therefore not quite so kitschy today. The course of events in Yasuhisa Serizawa’s manufacture, on the other hand, is real and of archaic force.

Namagiri – The battle begins

Auf der Zerlegebank werden die Fische halbiert und die Innereien entnommen. Die Hälften bestehen aus je zwei Filets mit den Namen Obushi und Mebushi / © Foto: Georg Berg
On the cutting bench, the fish are cut in half and the innards removed. / © Photo: Georg Berg

The next morning, work begins for Yasuhisa Seriwaza and a good 15 employees. Among them are his parents. Next to the basins, a kind of guillotine is brought into position. The head of the small tuna species bonito, weighing about five kilos, is cut off in the rattling machine. Then begins a process based on the division of labor, in which everyone knows their place and their task. Steam is rising, water is splashing out of the hoses. The work surface is constantly cleaned with a gush of fresh water. There is never any idling. The headless fish are cut in half with a knife and the innards removed. A job that requires strength and skill.

Yasuhisa Serizawa, rechts im Bild. Ihm gegenüber sein Vater, der mit weit über 80 Jahren noch mitzerteilt. Seine Mutter nimmt die Fischhälften und legt sie für den nächsten Arbeitsschritt in einen großen Metallkorb / © Foto: Georg Berg
Yasuhisa Serizawa, on the right in the picture. Opposite him is his father, who at well over 80 years of age is still helping out. Serizawa’s mother stands at the end of the bench, accepts the fish halves and places them in a round metal basket for the next step / © Photo: Georg Berg
Fein säuberlich zerlegt: An den vier Filets kann man jetzt schon die spätere Form des Honkare-Katsuobushi erkennen. Durch die mehrstufige Trocknung wird das Endprodukt viel kleiner sein. Auch alle anderen Teile des Fisches werden verwertet / © Foto: Georg Berg
Neatly dissected: You can already see the later shape of the honkare katsuobushi on the four fillets. The halves consist of two fillets each, named obushi and mebushi. Due to the multi-stage drying process, the final product will be much smaller. All other parts of the fish are also utilized / © Photo: Georg Berg

The Japanese attach great importance to the complete utilization of an animal. The heart of the tuna sits very close to the head. A worker kneels in front of a vat of fish heads and carefully detaches the tuna heart. It is considered a delicacy in Japan. The hearts are later picked up by a restaurant owner. At a small round table, two women squat on stools. With their small knives, they sort the offal. The stomach contents are removed. Almost everything else is collected for further processing for a fish paste that is later rubbed into the fillets.

Wirklich alles wird vom Fisch verwertet. Zwei Frauen säubern sogar die Mägen der Fische, damit diese ohne Inhalt zu einer Paste weiterverarbeitet werden können / © Foto: Georg Berg
Really everything is utilized from the fish. Two women even clean the stomachs of the fish so that they can be processed into a paste without the contents / © Photo: Georg Berg

Shakuju is a matter for the boss

The division of labor is as conscientious and calm as each half of the fish seems to have its place in the production process. There is little talking. The foreman, who has just detached the tuna hearts from the headboard, is now setting up a new workstation. Steam rises.

"Shakuju" ist absolute Chefsache. Für jedes Tauchbecken hat Serizawa eine eigene Uhr. Das Wasser darf nie kochen, es darf nur köcheln und der ganze Vorgang zwei Stunden nicht überschreiten / © Foto: Georg Berg
Shakuju is absolutely a matter for the boss. Yasuhisa Serizawa watches the temperature and stops the time / © Photo: Georg Berg

The immersion tanks for the boiling process have long since been brought up to operating temperature. And this temperature is 90 degrees. Rather than fish, it now smells of blood. The billowing steam gives this place the atmosphere of an eerily beautiful movie set.

Serizawa führt den Korb, Nikgao genannt, mit den Thunfischhälften in ein maßgeschneidertes Tauchbecken. Dies ist der sensibelste Part in der Herstellung. Denn das vorsichtige Köcheln des Fisches bestimmt seine spätere Form und ist Grundlage für die spätere Geschmacksintensität / © Foto: Georg Berg

Serizawa guides the basket, called a nikgao, containing the tuna halves into a custom-made dip tank. This is the most sensitive part of the production. This is because the careful simmering of the fish determines its shape and is the basis for the desired intensity of flavor. Shakuju is absolutely a matter for the chef. Serizawa has its own clock for each dip. The water must never boil, it must only simmer and the whole process must not exceed two hours.

The long tradition of tuna processing

In Nishi-Izu, people have been living off tuna for 1,500 years. It started with the preservation by sun drying. Later, salting was added to the sun. In the Edo period, about 360 years ago, the production of katsuobushi developed. Sun-drying and salting is preceded by simmering the fish fillets in 90-degree water.

„Honenuki“ heißt das manuelle Entgräten der Fischhälften, bei dem der nun in vier Filets geteilte Fisch möglichst unbeschadet bleiben soll / © Foto: Georg Berg
Honenuki is the name given to the manual deboning of the fish halves, during which the fish, now divided into four fillets, should remain as undamaged as possible / © Photo: Georg Berg

The next workstation is set up. The water is let in and a newly formed team begins the laborious process of deburring the fish halves. They are now split into two pieces, approaching their eventual shape. Despite great caution, pieces break off again and again during the deburring process. This blemish is leveled by the paste of fish guts. Each piece of fillet is rubbed and brought into shape. Syuzen (repair) is the name of this step.

„Baikan“ - Für das Räuchern wird nur hartes Holz wie Eiche verwendet. Bei diesem ersten Räuchervorgang, der bis spät in die Nacht geht, bewachen zwei Arbeiter für acht Stunden das Feuer / © Foto: Georg Berg
Baikan – Only hard wood such as oak is used for smoking. During this first smoking process, which goes on until late at night, two workers guard the fire for eight hours / © Photo: Georg Berg

After boning, the fish comes into contact with the smoker for the first time. The fillets are placed on wooden stretchers and stacked over a wood fire. 130 to 150 degrees has this first heat. It is a traditional smoking method. Only a handful of katsuobushi producers throughout Japan still smoke with these old ovens. This requires two people to watch the fire for about eight hours.

What makes katsuobushi like honkarebushi

Das Räucherholz ist Eiche. Im begehbaren Holzkohleofen wird per Hand getestet, ob der Fisch bereits trocken genug ist. Denn jeder Fisch ist anders und so bedarf es einer individuellen Prüfung / © Foto: Georg Berg
The wood used for smoking is oak. In the walk-in charcoal oven, the fish is tested by hand to see if it is already dry enough. Because every fish is different and so it requires an individual test / © Photo: Georg Berg

Then begins a process that is repeated ten times at Serizawa. The fillets go into the smokehouse for a day and then rest for a day. The internal residual moisture of the fillet permeates to the outside. The fish is put back into the smoking chamber. The residual moisture escapes to the outside and is dried again. At the end, the fish has a residual moisture of around 23 percent and can call itself Arabushi. But a lot of time and work will pass before the perfect bonito flake, honkarebushi, is achieved.

Während der Fermentation wird der Pilz immer wieder durch Sonneneinstrahlung in Schach gehalten und und die Fischfilets werden im Hof für mehrere Stunden auf Matten ausgebreitet, bevor sie wieder für weitere 20 Tage in Zedernfässern geschichtet werden / © Foto: Georg Berg
During fermentation, the fungus is repeatedly kept in check by exposure to sunlight, and the fish fillets are spread out on mats in the courtyard for several hours before being layered again in cedar barrels for another 20 days / © Photo: Georg Berg

Using the means of fermentation

Unlike the major factory producers in the country, Serizawa still brings fermentation into play at this point. This involves spraying the outer smoke crust of the fillets with Aspergillus Ripens and storing them in cedar barrels. This watering can fungus can stand up to high dryness. If the fish ferments too long, the mold culture does a great job and the fillets become soft like blue cheese, Serizawa explains.

Sonne und Schimmelkultur im Wechsel geben dem Honkare-Katsuobushi den angestrebten Feuchtigkeitsgrad von unter 20 Prozent / © Foto: Georg Berg
Alternating sunlight and mold culture give honkare katsuobushi the desired moisture level of less than 20 percent / © Photo: Georg Berg

To control the koji fungus, the fillets are placed in the sun. The entire courtyard of the manufactory is then covered with tatami mats. The fillets now look like whole fish again and form a beautiful pattern on the mat. After sunbathing, the mushroom has been given a damper, the fillets are wiped off and placed in the cedar barrel for another 20 days. This procedure is repeated six times. If the fish looks rather bluish at the beginning of this procedure, it turns beige-brown at the end. The desired effect is a further reduction of the water content with simultaneous extraction of umami.

Vor dem Hobel liegt das Endprodukt, ein hochwertiger Honkare-Katsuobushi. Getrocknet und fermentiert hat er die geringste Restfeuchte und ist ein natürlicher Geschmacksverstärker / © Foto: Georg Berg
In front of the slicer lies the final product, a high-quality honkare katsuobushi. Dried and fermented, it has the lowest residual moisture and is a natural flavor booster / © Photo: Georg Berg

Feather-light flavor booster

Six months after the bonito tuna is delivered to Yasuhisa Seriwaza’s Kanesa Bonito Manufactory, the fish has reached a water content of 17 percent. With the help of a plane, the fish is planed from tail to head. In order to know where the top and bottom are after six months of intensive treatment, part of the skin is left on the end of the tail. Freshly planed, the Honkarebushi has its most intense flavor. A real gourmet product. In stores and for everyday use in making daily miso soup, Japanese buy the sliced variety.

Nishi-Izu Shiu-katsuo Nudeln sind eine regionale Spezialität. Sie wird nur noch in Nish-Izu hergestellt und wurde schon mehrfach ausgezeichnet / © Foto: Georg Berg
Nishi-Izu Shiu-katsuo noodles are a regional specialty. They are only produced in Nish-Izu and have won several awards / © Photo: Georg Berg

Bonito in bast dress

Shio-katsuo, salted and sun-dried used to be even a means of payment to the administration. The custom of hanging it on the front door on New Year’s Day has survived to this day. After the New Year, the fish is cut up by the father and eaten with the family. Today, Serizawa is still the only producer in all of Japan that does this according to the old methods. The oldest way of preserving tuna is dying out. To preserve the taste of Shio-Katsuo and with it the tradition is another mission of Yasuhisa Serizawa.

Journalistin Angela Berg neben Yasuhisa Seriwaza mit dem traditionellen Shio-Katsuo, dem Bonito im Bastkleid / © Foto: Georg Berg
Angela Berg next to Yasuhisa Seriwaza with the traditional shio-katsuo, the bonito in raffia dress / © Photo: Georg Berg

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