10. THE BUSIEST FISH IN THE OCEAN

I wanted to find out more about the two key, umami-rich ingredients used to make dashi: konbu and katsuobushi. Konbu would have to wait until we headed north to Hokkaido the following week (this was now late September), but I wanted to see how katsuobushi was made while we were still in Tokyo.

Katsuobushi are dried and fermented fillets of the bonito fish, as hard as wood and dusty brown in color. In their whole state they look kind of like fossilized bananas but are usually sold pre-shaved in airtight bags. They crop up either as shavings, dancing bewitchingly in the heat atop various dishes, or steeped and then strained in dashi to add a deeply satisfying savoriness to soups and sauces. The shavings are fantastically moreish just eaten on their own from the bag, too, with an addictive smoky-citric flavor and a mildly fishy aftertaste. Fishiness aside, the closest comparison I can think of is the salty meatiness of a really good, paper-thin slice of pata negra ham. It really is that delicious.

*   *   *

Soon after my visit to Ajinomoto, I took the Shinkansen south from Tokyo to Yaizu, a fishing port midway between Tokyo and Nagoya (to my eternal gratitude, Lissen again agreed to entertain the children—this time with a trip to the Mori Art Museum and the aquarium). Yaizu is Katsuo Town, built on the money from processing bonito. Yaizu katsuobushi is famous throughout Japan; it’s a brand in its own right, with some of its output still made the traditional way, by drying the fillets in the sun.

The town was more prosperous than other rural communities I would see in Japan. The price they’d had to pay for that prosperity was apparent as soon I got out of the taxi. The air was heavy with the smell of smoking fish. To me it was deliciously tangy, but I could imagine one might grow immune to its charms if one lived with it all the time. The smell was accompanied by a cacophony of machinery and diesel engines, forklift trucks, and conveyor belts. As I approached the factory gates, there was an almighty rubbery clattering noise behind me as a truck tipped a load of silver-black, glistening torpedoes, together with a large quantity of bloody seawater, into a tank. My first sight of a real, whole bonito.

The Yaizu Fish Manufacturing Park is a town within a town made up of corrugated warehouses housing twenty-four factories. Each is in some way involved with processing every scrap of this dense, oily, red-fleshed fish, making everything from super-fresh sashimi to canned bonito. One company takes the guts and salts, pickles, and ferments them to be eaten as a delicacy; another makes calcium supplements for school meals from the dried, powdered bones. Even the essence from the liquid used to cook the bonito is recuperated and used to flavor instant ramen, and, of course, several make the katsuobushi itself. It is an incredible fish.

“Nothing is wasted here,” a spokesman for Yaizu explained as he showed me into the boardroom. “Even the guts and hearts are processed for fertilizer. Quantities of bonito are declining, and the number of ships catching them are decreasing, too. Even though the government [which controls prices] says the number of fish in the ocean is stable, we don’t agree. There are fewer fish to go after, oil costs mean it is more expensive to go after them, yet demand is rising, so we have to maximize the yield from every one we catch.”

Yaizu processes around thirteen thousand tons of katsuo each year—that’s about sixty thousand fish per day—but as recently as 2004, that figure was as high as eighteen thousand tons. I learned all this from what was about the tenth corporate video I had endured since arriving in Japan, all of them opening with the same shaky, synthesized strings and a portentous voice-over. As well as informing me that they “make the most of our blessings from the sea,” it did explain the bonito’s migration pattern: modori is the name given to katsuo returning from the north (specifically the southeast coast of Hokkaido) in the autumn, which are fatter and richer and mostly eaten raw or lightly grilled (bonito is considered a lower-grade fish to eat than tuna); while in spring the fish come from the south on the so-called Black Current, mostly from the Philippines, and are leaner and better for making katsuobushi. The migration is changing, however, with fish traveling farther north to spawn while the Black Current itself is changing, too.

I asked if they had tried ranching or farming bonito. “It has not yet become economically viable to farm bonito like tuna; they are too small and are even more active than tuna,” explained the spokesman. Apparently, bonito even swim in their sleep: especially industrious Japanese are said to “work like a katsuo.”

I was curious to see the process that takes the fish we had seen being tipped out of their tanker as we arrived and turns them into the dried fillets, like glockenspiel keys, that I had seen for sale in the shops in the outer part of Tsukiji.

We headed outside to take a look. The spokesman explained that the fish are defrosted and their heads and internal organs removed. After boiling, an army of local women fillet every one of those sixty thousand fish by hand—after cooking, the fish are fragile, and this is the only way of removing the spine and other bones while retaining the perfectly shaped fillets the aesthetically conscious Japanese demand. We visited one of the processing halls, a dark, strip-lit factory, smelly and steamy, its every surface coated in brown fish grease. Around fifty women in blue hygiene hats, wearing rubber gloves, with their sleeves rolled up, stood as the cooked fish passed by on conveyor belts. I watched one as she swiftly picked a fish up and turned it over in her hands a couple of times, dividing the four fillets from the skeleton, perfectly, in seconds. The bones disappeared down a hole to be taken off and ground up, while the fillets were placed carefully on a wire tray beside her.

Smoking and fermenting come next. Obviously, different types of wood will affect the final flavor. Some companies use konara oak, others cherrywood, but the flavor of the finished katsuobushi can also change according to how many times it is smoked: between ten and twenty is the norm to dry the flesh thoroughly until only about 20 percent of the water remains. We saw the vast smoking kilns, again caked in old fish goo, treacly and brown. The finest bonito of all, however, are cured in the sun for two days. There are records dating back to the Middle Ages of bonito being mold-cured in this way, and one company in Yaizu still prepares its bonito this way—weather permitting.

Next, the fillets are placed in a hot, humid storage area, like a huge oven, that has been impregnated with the Aspergillus glaucus mold. Some of the storage chambers are decades old and imbue the fillets with a unique flavor, each identifiable to a true katsuo connoisseur. As with miso, soy, and sake, this fermentation contributes greatly to the deep, complex flavor and umami power of katsuobushi. The mold creates flavorsome enzymes that turn the fish protein into amino acids, in particular a compound called inosine monophosphate (IMP). The process takes up to six weeks, during which the fillets will be taken back out into the sun to kill off the mold—perhaps several times—each time being returned to the chamber to grow a new layer, which deepens the flavor further. By the end, the fish fillets are hard as wood, ready for the final stage: shaving.

This is done using a katsuobushi kezuriki, an upside-down carpenter’s plane with a container underneath to catch the shavings. The best chefs will shave the katsuobushi fillets by hand, literally moments before they go into the dashi, as they start to lose flavor and aroma the moment they are shaved. Many use airtight bags of pre-shaved fillets, which you can buy in all Japanese supermarkets. Most home cooks, however, will use some kind of powdered form of instant dashi, most likely with an Ajinomoto label on it.

We ended up in a small shop selling some of the produce made nearby. The Yaizu spokesman showed me how to pick good katsuobushi fillets by gently tapping two together—the denser the fillets, the better their quality and flavor, and the sound they make should be almost metallic. (Also, should you find yourself out shopping for katsuobushi, Shizuo Tsuji, in A Simple Art, says that if there is a green tint to the mold, the fillet is too watery, and if it is yellow, too acidic.) He broke one in half to show me the rings, again, just like wood, the color ranging through its center from dark purple to brown. Apparently, I was the first Westerner ever to visit Yaizu, and, overcome by the honor, I rashly bought two whole fillets for a few thousand yen, not really thinking ahead that I didn’t have anything to shave them with, later realizing that a proper katsuobushi grater costs around a hundred dollars or so.

I still have the fillets. They remain at the bottom of my “too good to use” drawer, as yet unshaved. From time to time I take them out, sniff them fondly, and imagine how great they will one day taste.